diff --git a/crates/buzz-acp/src/acp.rs b/crates/buzz-acp/src/acp.rs
index 8a698954a0..b362de32f0 100644
--- a/crates/buzz-acp/src/acp.rs
+++ b/crates/buzz-acp/src/acp.rs
@@ -211,6 +211,10 @@ pub struct AcpClient {
     /// deltas. Both goose and buzz-agent emit this notification; goose gates
     /// on client capability advertisement, buzz-agent emits unconditionally.
     goose_usage: UsageTracker,
+    /// Accumulates `agent_message_chunk` text while a one-shot helper (the
+    /// `complete` subcommand) is capturing the agent's reply. `None` disables
+    /// capture — the normal harness path never allocates here.
+    captured_agent_text: Option<String>,
 }
 
 /// Recursively merge `overlay` into `base`, with `overlay` winning on scalar/shape
@@ -550,9 +554,23 @@ impl AcpClient {
             steering_supported: false,
             steer_rx: None,
             goose_usage: UsageTracker::default(),
+            captured_agent_text: None,
         })
     }
 
+    /// Start capturing `agent_message_chunk` text from `session/update`
+    /// notifications. Used by the one-shot `complete` subcommand to collect
+    /// the agent's reply text; the harness path never enables this.
+    pub fn begin_text_capture(&mut self) {
+        self.captured_agent_text = Some(String::new());
+    }
+
+    /// Take the text captured since [`begin_text_capture`](Self::begin_text_capture)
+    /// and disable capture.
+    pub fn take_captured_text(&mut self) -> String {
+        self.captured_agent_text.take().unwrap_or_default()
+    }
+
     /// Attach a local observer feed to this ACP client.
     pub fn set_observer(&mut self, observer: Option<ObserverHandle>, agent_index: usize) {
         self.observer = observer;
@@ -1715,6 +1733,9 @@ impl AcpClient {
             "agent_message_chunk" => {
                 if let Some(text) = update["content"]["text"].as_str() {
                     tracing::info!(target: "acp::stream", "{text}");
+                    if let Some(buffer) = self.captured_agent_text.as_mut() {
+                        buffer.push_str(text);
+                    }
                 }
                 false
             }
diff --git a/crates/buzz-acp/src/base_prompt.md b/crates/buzz-acp/src/base_prompt.md
index e360d24982..606a239b34 100644
--- a/crates/buzz-acp/src/base_prompt.md
+++ b/crates/buzz-acp/src/base_prompt.md
@@ -24,6 +24,27 @@ Run `buzz --help` or `buzz <group> --help` for full usage. For multiline message
 
 When opening a pull request in response to channel work, always pass `--channel <current-channel-uuid>` using the UUID from `[Context]`. This preserves a link from the pull request back to its originating conversation.
 
+## Sub-channels
+
+Sub-channels are focused working sessions under a main channel. They use the one-level naming convention `parent--sub`; a sub-channel cannot itself be a parent.
+
+Spawn one with `buzz channels create --name <slug> --parent <parent-channel-id> --description "<task>"`. The sub-channel inherits the parent's type and visibility; the command constructs the full name, announces the spawn in the parent, and updates both canvases.
+
+Only ever add someone to a sub-channel if they are already a member of its parent. Humans may join a sub-channel to steer the work or stay out of it.
+
+Before considering the task done, post a final summary to the parent channel as a thread reply to the spawn announcement. The sub-channel canvas records both the parent channel and the announcement event ID under `spawned-from`.
+
+## Sharing Buzz Links in Slack
+
+When sharing a link to Buzz work in Slack, always use this exact format:
+
+> :buzz: Joah is working on this in Buzz. [Join #<channel-name> to participate](buzz://message?channel=<uuid>&id=<event-id>)
+
+- Start with the `:buzz:` Slack emoji. Do not add a 🤖 AI-agent disclaimer to these messages — this is a deliberate exception.
+- `buzz://` has no channel-only deep link; link the relevant message or thread root, which opens the channel in Desktop.
+- ALWAYS wait until the channel's name is finalized before sending. Freshly spawned channels get renamed shortly after creation; verify the current name with `buzz channels list` immediately before posting, and if the channel still carries a placeholder or parent name, wait for the rename to land first.
+- Whenever Joah gives you a link to a Slack message as context for work, ALWAYS post the Buzz-link message as a reply in that Slack thread so watchers know where the work is happening.
+
 ## Conversational Agent Creation
 
 When someone asks to create an agent, ask for at most two things: the agent's name and what it should do day-to-day. Turn the user's rough purpose into the `--system-prompt` yourself; do not separately ask for purpose, tone, constraints, access, runtime, provider, or model unless the user's request is genuinely ambiguous.
diff --git a/crates/buzz-acp/src/config.rs b/crates/buzz-acp/src/config.rs
index dab61be30a..be9d67d6d0 100644
--- a/crates/buzz-acp/src/config.rs
+++ b/crates/buzz-acp/src/config.rs
@@ -201,6 +201,35 @@ pub struct AuthAgentArgs {
     pub agent_args: Vec<String>,
 }
 
+/// CLI args for `buzz-acp complete` — one-shot prompt completion via the
+/// configured agent. Spawns the agent, opens a session, sends a single
+/// prompt, and prints the accumulated agent reply text. No relay connection.
+#[derive(Debug, Parser)]
+#[command(
+    name = "buzz-acp complete",
+    about = "One-shot prompt completion via the configured agent"
+)]
+pub struct CompleteArgs {
+    #[command(flatten)]
+    pub agent: AuthAgentArgs,
+
+    /// Prompt text to send to the agent.
+    #[arg(long)]
+    pub prompt: String,
+
+    /// Optional system prompt for the session.
+    #[arg(long)]
+    pub system_prompt: Option<String>,
+
+    /// Optional model id to select via `session/set_model` (best-effort).
+    #[arg(long)]
+    pub model: Option<String>,
+
+    /// Output structured JSON (`{"text": ...}`) instead of raw text.
+    #[arg(long)]
+    pub json: bool,
+}
+
 /// CLI args for `buzz-acp auth-methods` — query adapter-advertised login methods.
 #[derive(Debug, Parser)]
 #[command(
diff --git a/crates/buzz-acp/src/lib.rs b/crates/buzz-acp/src/lib.rs
index 403512a322..a7f4ef0298 100644
--- a/crates/buzz-acp/src/lib.rs
+++ b/crates/buzz-acp/src/lib.rs
@@ -30,7 +30,7 @@ use buzz_core::observer::{
 };
 use clap::Parser;
 use config::{
-    AuthAgentArgs, AuthMethodsArgs, AuthenticateArgs, Config, DedupMode, ModelsArgs,
+    AuthAgentArgs, AuthMethodsArgs, AuthenticateArgs, CompleteArgs, Config, DedupMode, ModelsArgs,
     MultipleEventHandling, RespondTo, SubscribeMode,
 };
 use filter::SubscriptionRule;
@@ -1251,6 +1251,16 @@ async fn tokio_main() -> Result<()> {
         return run_models(args).await;
     }
 
+    if is_subcommand("complete") {
+        let filtered: Vec<String> = std::env::args()
+            .enumerate()
+            .filter(|(i, _)| *i != 1)
+            .map(|(_, a)| a)
+            .collect();
+        let args = CompleteArgs::parse_from(&filtered);
+        return run_complete(args).await;
+    }
+
     if is_subcommand("auth-methods") {
         let filtered: Vec<String> = std::env::args()
             .enumerate()
@@ -4176,6 +4186,98 @@ async fn run_models(args: ModelsArgs) -> Result<()> {
     Ok(())
 }
 
+/// Setup timeout for `buzz-acp complete` (spawn + initialize + session/new).
+/// Longer than [`MODELS_TIMEOUT`] because agents cold-start here (goose can
+/// take >10s to initialize its first session).
+const COMPLETE_SETUP_TIMEOUT: Duration = Duration::from_secs(30);
+
+/// Idle timeout for `buzz-acp complete` — resets on any agent stdout activity.
+const COMPLETE_IDLE_TIMEOUT: Duration = Duration::from_secs(30);
+
+/// Hard wall-clock cap for `buzz-acp complete`.
+const COMPLETE_MAX_DURATION: Duration = Duration::from_secs(90);
+
+/// Flow: spawn → initialize → session/new → session/prompt → print captured
+/// agent text → shutdown. No relay connection, no MCP servers.
+///
+/// Powers desktop features that need a bounded request/response completion
+/// from the configured agent (e.g. Developer Mode channel naming).
+async fn run_complete(args: CompleteArgs) -> Result<()> {
+    let agent_args = config::normalize_agent_args(&args.agent.agent_command, args.agent.agent_args);
+    let cwd = std::env::current_dir()
+        .unwrap_or_else(|_| std::path::PathBuf::from("/"))
+        .to_string_lossy()
+        .to_string();
+
+    // Spawn outside the timeout so we always own the child for cleanup.
+    let mut client =
+        match AcpClient::spawn(&args.agent.agent_command, &agent_args, &[], false).await {
+            Ok(c) => c,
+            Err(e) => {
+                eprintln!("error: failed to spawn agent: {e}");
+                std::process::exit(1);
+            }
+        };
+
+    let setup_result = tokio::time::timeout(COMPLETE_SETUP_TIMEOUT, async {
+        client.initialize().await?;
+        let session = client
+            .session_new_full(&cwd, vec![], args.system_prompt.as_deref(), None)
+            .await?;
+        Ok::<_, acp::AcpError>(session.session_id)
+    })
+    .await;
+
+    let session_id = match setup_result {
+        Ok(Ok(id)) => id,
+        Ok(Err(e)) => {
+            client.shutdown().await;
+            eprintln!("error: agent communication failed: {e}");
+            std::process::exit(1);
+        }
+        Err(_) => {
+            client.shutdown().await;
+            eprintln!("error: agent timed out ({COMPLETE_SETUP_TIMEOUT:?})");
+            std::process::exit(1);
+        }
+    };
+
+    // Best-effort model selection — not all agents support session/set_model.
+    if let Some(model) = &args.model {
+        let _ = client.session_set_model(&session_id, model).await;
+    }
+
+    client.begin_text_capture();
+    let prompt_result = client
+        .session_prompt_with_idle_timeout(
+            &session_id,
+            &args.prompt,
+            COMPLETE_IDLE_TIMEOUT,
+            COMPLETE_MAX_DURATION,
+        )
+        .await;
+    let text = client.take_captured_text();
+    client.shutdown().await;
+
+    if let Err(e) = prompt_result {
+        eprintln!("error: prompt failed: {e}");
+        std::process::exit(1);
+    }
+
+    let trimmed = text.trim();
+    if trimmed.is_empty() {
+        eprintln!("error: agent returned no message text");
+        std::process::exit(1);
+    }
+
+    if args.json {
+        println!("{}", serde_json::json!({ "text": trimmed }));
+    } else {
+        println!("{trimmed}");
+    }
+    Ok(())
+}
+
 fn build_mcp_servers(config: &Config) -> Vec<McpServer> {
     if config.mcp_command.is_empty() {
         return vec![];
diff --git a/crates/buzz-cli/src/commands/channels.rs b/crates/buzz-cli/src/commands/channels.rs
index 42844bf1e0..5222c28bc6 100644
--- a/crates/buzz-cli/src/commands/channels.rs
+++ b/crates/buzz-cli/src/commands/channels.rs
@@ -328,6 +328,253 @@ pub async fn cmd_create_channel(
     Ok(())
 }
 
+fn sanitize_sub_channel_name(name: &str) -> Result<String, CliError> {
+    let mut sanitized = String::new();
+    let mut previous_hyphen = false;
+    for ch in name.to_ascii_lowercase().chars() {
+        if ch.is_ascii_alphanumeric() {
+            sanitized.push(ch);
+            previous_hyphen = false;
+        } else if !previous_hyphen && !sanitized.is_empty() {
+            sanitized.push('-');
+            previous_hyphen = true;
+        }
+    }
+    let sanitized = sanitized.trim_matches('-').to_string();
+    if sanitized.is_empty() {
+        return Err(CliError::Usage(
+            "--name is empty after sub-channel name sanitization".into(),
+        ));
+    }
+    Ok(sanitized)
+}
+
+fn construct_sub_channel_name(parent_name: &str, name: &str) -> Result<String, CliError> {
+    if parent_name.contains("--") {
+        return Err(CliError::Usage(
+            "sub-channels support one nesting level; the parent name cannot contain '--'".into(),
+        ));
+    }
+    Ok(format!(
+        "{parent_name}--{}",
+        sanitize_sub_channel_name(name)?
+    ))
+}
+
+fn append_sub_channel_to_canvas(canvas: &str, sub_name: &str, task: &str) -> String {
+    let bullet = format!("- #{sub_name} — {}", task.lines().next().unwrap_or(task));
+    let heading = "## Sub-channels";
+    let mut canvas = canvas.to_string();
+    let Some(heading_start) = canvas.lines().position(|line| line.trim() == heading) else {
+        canvas.push_str("\n\n## Sub-channels\n");
+        canvas.push_str(&bullet);
+        canvas.push('\n');
+        return canvas;
+    };
+
+    let lines: Vec<&str> = canvas.lines().collect();
+    let section_end = lines[heading_start + 1..]
+        .iter()
+        .position(|line| line.starts_with("## "))
+        .map(|offset| heading_start + 1 + offset)
+        .unwrap_or(lines.len());
+    let insert_line = (heading_start + 1..section_end)
+        .rfind(|&index| lines[index].starts_with("- #"))
+        .map(|index| index + 1)
+        .unwrap_or(heading_start + 1);
+    let mut output = lines[..insert_line].join("\n");
+    if !output.is_empty() {
+        output.push('\n');
+    }
+    output.push_str(&bullet);
+    if insert_line < lines.len() {
+        output.push('\n');
+        output.push_str(&lines[insert_line..].join("\n"));
+    } else {
+        output.push('\n');
+    }
+    output
+}
+
+async fn resolve_parent_channel(
+    client: &BuzzClient,
+    parent: &str,
+) -> Result<ChannelSummary, CliError> {
+    let filter = if Uuid::parse_str(parent).is_ok() {
+        serde_json::json!({"kinds": [39000], "#d": [parent], "limit": 1})
+    } else {
+        serde_json::json!({"kinds": [39000]})
+    };
+    let matches: Vec<ChannelSummary> = client
+        .query_paginated(filter, 1000)
+        .await?
+        .iter()
+        .filter_map(ChannelSummary::from_event)
+        .filter(|channel| channel.channel_id == parent || channel.name.eq_ignore_ascii_case(parent))
+        .collect();
+    match matches.as_slice() {
+        [channel] => Ok(ChannelSummary {
+            channel_id: channel.channel_id.clone(),
+            name: channel.name.clone(),
+            channel_type: channel.channel_type.clone(),
+            visibility: channel.visibility.clone(),
+            archived: channel.archived,
+            about: channel.about.clone(),
+            topic: channel.topic.clone(),
+            purpose: channel.purpose.clone(),
+        }),
+        [] => Err(CliError::Usage(format!(
+            "parent channel '{parent}' not found"
+        ))),
+        _ => Err(CliError::Usage(format!(
+            "multiple channels are named '{parent}'; use the parent channel UUID"
+        ))),
+    }
+}
+
+async fn cmd_create_sub_channel(
+    client: &BuzzClient,
+    parent_ref: &str,
+    name: &str,
+    channel_type: Option<&str>,
+    visibility: Option<&str>,
+    description: Option<&str>,
+    ttl: Option<i64>,
+) -> Result<(), CliError> {
+    let parent = resolve_parent_channel(client, parent_ref).await?;
+    let parent_uuid = parse_uuid(&parent.channel_id)?;
+    let member_filter =
+        serde_json::json!({"kinds": [39002], "#d": [&parent.channel_id], "limit": 1});
+    let member_events = client.query_paginated(member_filter, 1).await?;
+    let caller = client.keys().public_key().to_hex();
+    if !member_events
+        .first()
+        .map(extract_p_tags)
+        .unwrap_or_default()
+        .iter()
+        .any(|member| member == &caller)
+    {
+        return Err(CliError::Usage(
+            "sub-channel members must be members of the parent; the caller is not a parent member"
+                .into(),
+        ));
+    }
+
+    let final_name = construct_sub_channel_name(&parent.name, name)?;
+    let channel_type = channel_type
+        .or(parent.channel_type.as_deref())
+        .ok_or_else(|| CliError::Other("parent channel has no type".into()))?;
+    let visibility = visibility
+        .or(parent.visibility.as_deref())
+        .map(|value| if value == "public" { "open" } else { value })
+        .ok_or_else(|| CliError::Other("parent channel has no visibility".into()))?;
+    let ttl = ttl.map(validate_ttl_seconds).transpose()?;
+    let sub_uuid = Uuid::new_v4();
+    let vis = match visibility {
+        "open" => buzz_sdk::Visibility::Open,
+        "private" => buzz_sdk::Visibility::Private,
+        other => {
+            return Err(CliError::Other(format!(
+                "invalid parent visibility: {other}"
+            )))
+        }
+    };
+    let kind = match channel_type {
+        "stream" => buzz_sdk::ChannelKind::Stream,
+        "forum" => buzz_sdk::ChannelKind::Forum,
+        other => {
+            return Err(CliError::Other(format!(
+                "invalid parent channel type: {other}"
+            )))
+        }
+    };
+    let builder = buzz_sdk::build_create_channel(
+        sub_uuid,
+        &final_name,
+        Some(vis),
+        Some(kind),
+        description,
+        ttl,
+    )
+    .map_err(|e| CliError::Other(format!("build_create_channel failed: {e}")))?;
+    let create_response = client.submit_event(client.sign_event(builder)?).await?;
+    let task = description.unwrap_or(&final_name);
+
+    let announcement = format!("→ spawned #{final_name}");
+    let announcement_result: Result<String, CliError> = async {
+        let builder = buzz_sdk::build_message(parent_uuid, &announcement, None, &[], false, &[])
+            .map_err(|e| CliError::Other(format!("build_message failed: {e}")))?;
+        let response = client.submit_event(client.sign_event(builder)?).await?;
+        serde_json::from_str::<serde_json::Value>(&response)
+            .ok()
+            .and_then(|value| value["event_id"].as_str().map(str::to_string))
+            .ok_or_else(|| CliError::Other("announcement response omitted event_id".into()))
+    }
+    .await;
+
+    let announcement_id = match announcement_result {
+        Ok(id) => id,
+        Err(error) => {
+            eprintln!("warning: channel created, but parent announcement failed: {error}");
+            print_sub_channel_response(&create_response, &sub_uuid, &final_name, None);
+            return Ok(());
+        }
+    };
+
+    let sub_canvas = format!(
+        "# Sub-channel of #{}\n\n- parent: #{} ({})\n- spawned-from: {}\n- task: {}\n\nWhen the work here is complete, post a summary to #{} as a thread reply to the spawn announcement (event {}). Every member of this sub-channel must be a member of #{}.",
+        parent.name, parent.name, parent.channel_id, announcement_id, task, parent.name, announcement_id, parent.name
+    );
+    if let Err(error) = set_canvas(client, sub_uuid, &sub_canvas).await {
+        eprintln!("warning: channel created, but sub-channel canvas setup failed: {error}");
+    }
+
+    let parent_canvas_result: Result<(), CliError> = async {
+        let filter = serde_json::json!({"kinds": [40100], "#h": [&parent.channel_id], "limit": 1});
+        let events = client.query_paginated(filter, 1).await?;
+        let current = events
+            .first()
+            .and_then(|event| event.get("content"))
+            .and_then(|content| content.as_str())
+            .unwrap_or("");
+        let updated = append_sub_channel_to_canvas(current, &final_name, task);
+        set_canvas(client, parent_uuid, &updated).await
+    }
+    .await;
+    if let Err(error) = parent_canvas_result {
+        eprintln!("warning: channel created, but parent canvas update failed: {error}");
+    }
+    print_sub_channel_response(
+        &create_response,
+        &sub_uuid,
+        &final_name,
+        Some(&announcement_id),
+    );
+    Ok(())
+}
+
+async fn set_canvas(client: &BuzzClient, channel: Uuid, content: &str) -> Result<(), CliError> {
+    let builder = buzz_sdk::build_set_canvas(channel, content)
+        .map_err(|e| CliError::Other(format!("build_set_canvas failed: {e}")))?;
+    client.submit_event(client.sign_event(builder)?).await?;
+    Ok(())
+}
+
+fn print_sub_channel_response(
+    response: &str,
+    channel_id: &Uuid,
+    name: &str,
+    announcement_event_id: Option<&str>,
+) {
+    let normalized = normalize_write_response(response);
+    let mut output: serde_json::Value =
+        serde_json::from_str(&normalized).unwrap_or_else(|_| serde_json::json!({}));
+    output["channel_id"] = serde_json::json!(channel_id);
+    output["name"] = serde_json::json!(name);
+    output["announcement_event_id"] = serde_json::json!(announcement_event_id);
+    println!("{output}");
+}
+
 /// A resolved live managed-agent instance backing a template persona slug.
 #[derive(Debug, Clone, PartialEq, Eq, Serialize)]
 struct ResolvedAgent {
@@ -1092,6 +1339,7 @@ pub async fn dispatch(
             description,
             ttl,
             template,
+            parent,
             templates_file,
         } => {
             if let Some(template_name) = template {
@@ -1106,6 +1354,23 @@ pub async fn dispatch(
                     ttl,
                 )
                 .await
+            } else if let Some(parent) = parent {
+                cmd_create_sub_channel(
+                    client,
+                    &parent,
+                    &name,
+                    channel_type
+                        .as_ref()
+                        .map(|value| value.to_string())
+                        .as_deref(),
+                    visibility
+                        .as_ref()
+                        .map(|value| value.to_string())
+                        .as_deref(),
+                    description.as_deref(),
+                    ttl,
+                )
+                .await
             } else {
                 // required_unless_present = "template" guarantees these are
                 // Some when template is None.
@@ -1176,10 +1441,10 @@ pub async fn dispatch_canvas(cmd: crate::CanvasCmd, client: &BuzzClient) -> Resu
 #[cfg(test)]
 mod tests {
     use super::{
-        apply_cardinality_rule, build_template_report, cmd_set_add_policy,
-        finalize_roster_resolution, name_matches, resolve_roster_with_archive_filter,
-        validate_ttl_seconds, ArchivedExclusion, ChannelSummary, ResolvedAgent, RosterResolution,
-        SkippedSlug,
+        append_sub_channel_to_canvas, apply_cardinality_rule, build_template_report,
+        cmd_set_add_policy, construct_sub_channel_name, finalize_roster_resolution, name_matches,
+        resolve_roster_with_archive_filter, validate_ttl_seconds, ArchivedExclusion,
+        ChannelSummary, ResolvedAgent, RosterResolution, SkippedSlug,
     };
     use crate::client::BuzzClient;
     use crate::CliError;
@@ -1189,6 +1454,34 @@ mod tests {
         json!({ "tags": tags })
     }
 
+    #[test]
+    fn sanitizes_and_constructs_sub_channel_names() {
+        assert_eq!(
+            construct_sub_channel_name("engineering", "  API / Client---Work! ").unwrap(),
+            "engineering--api-client-work"
+        );
+        assert!(construct_sub_channel_name("engineering", "💥").is_err());
+        assert!(construct_sub_channel_name("engineering--api", "work").is_err());
+    }
+
+    #[test]
+    fn appends_sub_channel_section_and_uses_first_task_line() {
+        assert_eq!(
+            append_sub_channel_to_canvas("# Parent", "parent--api", "Build API\nDetails"),
+            "# Parent\n\n## Sub-channels\n- #parent--api — Build API\n"
+        );
+    }
+
+    #[test]
+    fn appends_sub_channel_bullet_after_existing_bullets() {
+        let canvas =
+            "# Parent\n\n## Sub-channels\n- #parent--one — One\n\nNotes\n\n## Links\n- link";
+        assert_eq!(
+            append_sub_channel_to_canvas(canvas, "parent--two", "Two"),
+            "# Parent\n\n## Sub-channels\n- #parent--one — One\n- #parent--two — Two\n\nNotes\n\n## Links\n- link"
+        );
+    }
+
     #[test]
     fn from_event_extracts_known_tags() {
         let ev = event(json!([
diff --git a/crates/buzz-cli/src/lib.rs b/crates/buzz-cli/src/lib.rs
index 02a58a618e..53a7d2a6c2 100644
--- a/crates/buzz-cli/src/lib.rs
+++ b/crates/buzz-cli/src/lib.rs
@@ -544,17 +544,17 @@ pub enum ChannelsCmd {
     },
     /// Create a new channel
     #[command(
-        after_help = "Examples:\n  buzz channels create --name general --type stream --visibility open\n  buzz channels create --name design --type forum --visibility open --description \"Design discussions\"\n  buzz channels create --name standup --type stream --visibility open --ttl 3600  # ephemeral, archived after 1h idle\n  buzz channels create --name project-x --template \"Buzz Team\"  # type/visibility/canvas/roster from the template; explicit flags override"
+        after_help = "Examples:\n  buzz channels create --name general --type stream --visibility open\n  buzz channels create --name design --type forum --visibility open --description \"Design discussions\"\n  buzz channels create --name standup --type stream --visibility open --ttl 3600  # ephemeral, archived after 1h idle\n  buzz channels create --name implementation --parent general --description \"Implement the feature\"\n  buzz channels create --name project-x --template \"Buzz Team\"  # type/visibility/canvas/roster from the template; explicit flags override"
     )]
     Create {
         /// Channel name
         #[arg(long)]
         name: String,
         /// Channel type. Required unless --template supplies one.
-        #[arg(long = "type", value_enum, required_unless_present = "template")]
+        #[arg(long = "type", value_enum, required_unless_present_any = ["template", "parent"])]
         channel_type: Option<ChannelType>,
         /// Channel visibility. Required unless --template supplies one.
-        #[arg(long, value_enum, required_unless_present = "template")]
+        #[arg(long, value_enum, required_unless_present_any = ["template", "parent"])]
         visibility: Option<ChannelVisibility>,
         /// Channel description
         #[arg(long)]
@@ -568,6 +568,9 @@ pub enum ChannelsCmd {
         /// its agent roster against the relay to add as members.
         #[arg(long)]
         template: Option<String>,
+        /// Parent channel UUID or exact name. Creates a one-level sub-channel.
+        #[arg(long, conflicts_with = "template", value_name = "CHANNEL")]
+        parent: Option<String>,
         /// Override the channel-templates.json path (default: the desktop
         /// app's prod app-data dir). Mainly for the dev store or testing.
         #[arg(long, value_name = "PATH")]
diff --git a/desktop/package.json b/desktop/package.json
index 2226a0cb12..7d1ad32f61 100644
--- a/desktop/package.json
+++ b/desktop/package.json
@@ -30,6 +30,7 @@
     "@emoji-mart/data": "^1.2.1",
     "@emoji-mart/react": "^1.1.1",
     "@fontsource-variable/inter": "^5.2.8",
+    "@fontsource-variable/jetbrains-mono": "^5.3.0",
     "@mediapipe/tasks-vision": "^0.10.35",
     "@radix-ui/react-alert-dialog": "^1.1.15",
     "@radix-ui/react-avatar": "^1.1.11",
diff --git a/desktop/playwright.config.ts b/desktop/playwright.config.ts
index 459fa75743..5429eaec43 100644
--- a/desktop/playwright.config.ts
+++ b/desktop/playwright.config.ts
@@ -27,6 +27,16 @@ export default defineConfig({
         "**/channels.spec.ts",
         "**/channel-shared-header-backdrop.spec.ts",
         "**/channel-composer-overflow.spec.ts",
+        "**/dev-mode-overflow.spec.ts",
+        "**/dev-mode-members.spec.ts",
+        "**/dev-mode-mentions.spec.ts",
+        "**/dev-mode-palette.spec.ts",
+        "**/dev-mode-shortcuts.spec.ts",
+        "**/dev-mode-composer-default.spec.ts",
+        "**/dev-mode-first-reply.spec.ts",
+        "**/dev-mode-sub-channels.spec.ts",
+        "**/dev-mode-unread.spec.ts",
+        "**/dev-mode-media.spec.ts",
         "**/badge.spec.ts",
         "**/channel-browser.spec.ts",
         "**/channel-add-screenshots.spec.ts",
diff --git a/desktop/public/sounds/bong.mp3 b/desktop/public/sounds/bong.mp3
index a62f2a442f..e1e6f17daf 100644
Binary files a/desktop/public/sounds/bong.mp3 and b/desktop/public/sounds/bong.mp3 differ
diff --git a/desktop/public/sounds/bong.svg b/desktop/public/sounds/bong.svg
index 9088087299..de559051a4 100644
--- a/desktop/public/sounds/bong.svg
+++ b/desktop/public/sounds/bong.svg
@@ -1 +1 @@
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+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 200 80" fill="currentColor" aria-hidden="true"><rect x="1.67" y="38.00" width="5" height="4.00" rx="2.50"/><rect x="10.00" y="34.10" width="5" height="11.80" rx="2.50"/><rect x="18.33" y="2.00" width="5" height="76.00" rx="2.50"/><rect x="26.67" y="6.58" width="5" height="66.85" rx="2.50"/><rect x="35.00" y="10.66" width="5" height="58.68" rx="2.50"/><rect x="43.33" y="12.82" width="5" height="54.36" rx="2.50"/><rect x="51.67" y="18.33" width="5" height="43.34" rx="2.50"/><rect x="60.00" y="24.53" width="5" height="30.95" rx="2.50"/><rect x="68.33" y="24.65" width="5" height="30.70" rx="2.50"/><rect x="76.67" y="22.88" width="5" height="34.25" rx="2.50"/><rect x="85.00" y="28.68" width="5" height="22.64" rx="2.50"/><rect x="93.33" y="33.36" width="5" height="13.27" rx="2.50"/><rect x="101.67" y="31.32" width="5" height="17.35" rx="2.50"/><rect x="110.00" y="34.19" width="5" height="11.62" rx="2.50"/><rect x="118.33" y="35.87" width="5" height="8.26" rx="2.50"/><rect x="126.67" y="35.78" width="5" height="8.44" rx="2.50"/><rect x="135.00" y="36.15" width="5" height="7.71" rx="2.50"/><rect x="143.33" y="37.41" width="5" height="5.17" rx="2.50"/><rect x="151.67" y="37.55" width="5" height="4.90" rx="2.50"/><rect x="160.00" y="37.83" width="5" height="4.34" rx="2.50"/><rect x="168.33" y="38.00" width="5" height="4.00" rx="2.50"/><rect x="176.67" y="38.00" width="5" height="4.00" rx="2.50"/><rect x="185.00" y="38.00" width="5" height="4.00" rx="2.50"/><rect x="193.33" y="38.00" width="5" height="4.00" rx="2.50"/></svg>
diff --git a/desktop/public/sounds/boo.mp3 b/desktop/public/sounds/boo.mp3
index 1d672a7d94..9431dc1188 100644
Binary files a/desktop/public/sounds/boo.mp3 and b/desktop/public/sounds/boo.mp3 differ
diff --git a/desktop/public/sounds/boo.svg b/desktop/public/sounds/boo.svg
index 977037bd3f..0190f87326 100644
--- a/desktop/public/sounds/boo.svg
+++ b/desktop/public/sounds/boo.svg
@@ -1 +1 @@
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diff --git a/desktop/public/sounds/dng.mp3 b/desktop/public/sounds/dng.mp3
index 29b111b10a..132c51f64a 100644
Binary files a/desktop/public/sounds/dng.mp3 and b/desktop/public/sounds/dng.mp3 differ
diff --git a/desktop/public/sounds/dng.svg b/desktop/public/sounds/dng.svg
index b702b0534e..cc779fb9fc 100644
--- a/desktop/public/sounds/dng.svg
+++ b/desktop/public/sounds/dng.svg
@@ -1 +1 @@
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diff --git a/desktop/public/sounds/doo.mp3 b/desktop/public/sounds/doo.mp3
index 6eb8f3b56e..fa9190b7ba 100644
Binary files a/desktop/public/sounds/doo.mp3 and b/desktop/public/sounds/doo.mp3 differ
diff --git a/desktop/public/sounds/doo.svg b/desktop/public/sounds/doo.svg
index 5fe260a236..a1a6e21bf5 100644
--- a/desktop/public/sounds/doo.svg
+++ b/desktop/public/sounds/doo.svg
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diff --git a/desktop/public/sounds/doodone.mp3 b/desktop/public/sounds/doodone.mp3
index c21ee7ad01..f65b8a862a 100644
Binary files a/desktop/public/sounds/doodone.mp3 and b/desktop/public/sounds/doodone.mp3 differ
diff --git a/desktop/public/sounds/doodone.svg b/desktop/public/sounds/doodone.svg
index bc6275de48..9433f41e22 100644
--- a/desktop/public/sounds/doodone.svg
+++ b/desktop/public/sounds/doodone.svg
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diff --git a/desktop/public/sounds/doong.mp3 b/desktop/public/sounds/doong.mp3
index 7c81649b91..8ece1d4ed1 100644
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diff --git a/desktop/public/sounds/doong.svg b/desktop/public/sounds/doong.svg
index 43728d02b4..d16d2db368 100644
--- a/desktop/public/sounds/doong.svg
+++ b/desktop/public/sounds/doong.svg
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diff --git a/desktop/public/sounds/doop.mp3 b/desktop/public/sounds/doop.mp3
index bbece1cb73..84fa111eb1 100644
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diff --git a/desktop/public/sounds/doop.svg b/desktop/public/sounds/doop.svg
index 4fdce28a34..6891b44b5c 100644
--- a/desktop/public/sounds/doop.svg
+++ b/desktop/public/sounds/doop.svg
@@ -1 +1 @@
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diff --git a/desktop/public/sounds/flirl.mp3 b/desktop/public/sounds/flirl.mp3
index 1edaa772ef..229258ab86 100644
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diff --git a/desktop/public/sounds/flirl.svg b/desktop/public/sounds/flirl.svg
index 5daa5e2a4b..08df112ebc 100644
--- a/desktop/public/sounds/flirl.svg
+++ b/desktop/public/sounds/flirl.svg
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diff --git a/desktop/public/sounds/flutter.mp3 b/desktop/public/sounds/flutter.mp3
index f6b7e3db6e..807c19b091 100644
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diff --git a/desktop/public/sounds/flutter.svg b/desktop/public/sounds/flutter.svg
index 81a87769cb..e470f61721 100644
--- a/desktop/public/sounds/flutter.svg
+++ b/desktop/public/sounds/flutter.svg
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diff --git a/desktop/public/sounds/oh-no.mp3 b/desktop/public/sounds/oh-no.mp3
index c95b6dfb56..65c6ac6b25 100644
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diff --git a/desktop/public/sounds/oh-no.svg b/desktop/public/sounds/oh-no.svg
index 26ad14a5b4..36e127bac5 100644
--- a/desktop/public/sounds/oh-no.svg
+++ b/desktop/public/sounds/oh-no.svg
@@ -1 +1 @@
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diff --git a/desktop/public/sounds/ping.mp3 b/desktop/public/sounds/ping.mp3
index 9cb4dc6352..4210dc3763 100644
Binary files a/desktop/public/sounds/ping.mp3 and b/desktop/public/sounds/ping.mp3 differ
diff --git a/desktop/public/sounds/ping.svg b/desktop/public/sounds/ping.svg
index c96cfbdea4..d0df0b4b9f 100644
--- a/desktop/public/sounds/ping.svg
+++ b/desktop/public/sounds/ping.svg
@@ -1 +1 @@
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diff --git a/desktop/public/sounds/unison.mp3 b/desktop/public/sounds/unison.mp3
index 143119017e..5c6495ae4d 100644
Binary files a/desktop/public/sounds/unison.mp3 and b/desktop/public/sounds/unison.mp3 differ
diff --git a/desktop/public/sounds/unison.svg b/desktop/public/sounds/unison.svg
index 6759d3df77..38ed6754de 100644
--- a/desktop/public/sounds/unison.svg
+++ b/desktop/public/sounds/unison.svg
@@ -1 +1 @@
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diff --git a/desktop/src-tauri/src/commands/agent_completion.rs b/desktop/src-tauri/src/commands/agent_completion.rs
new file mode 100644
index 0000000000..16e3cf7536
--- /dev/null
+++ b/desktop/src-tauri/src/commands/agent_completion.rs
@@ -0,0 +1,111 @@
+use tauri::{AppHandle, State};
+
+use super::agent_model_process::run_acp_helper_subprocess;
+use super::agent_models::{agent_model_discovery_config, AgentModelDiscoveryConfig};
+
+use crate::{
+    app_state::AppState,
+    managed_agents::{
+        discovery_env_with_baked_floor, known_acp_runtime, load_global_agent_config,
+        load_managed_agents, load_personas, missing_command_message, resolve_command,
+        runtime_metadata_env_vars, user_facing_harness_error,
+    },
+};
+
+/// Run one bounded prompt through a managed agent and return its reply text.
+///
+/// Spawns a short-lived `buzz-acp complete` subprocess against the agent's
+/// effective harness config (same descriptor resolution as spawn/model
+/// discovery). No relay connection — the exchange never appears in any
+/// channel. Powers Developer Mode channel naming.
+#[tauri::command]
+pub async fn generate_agent_completion(
+    pubkey: String,
+    prompt: String,
+    system_prompt: Option<String>,
+    app: AppHandle,
+    state: State<'_, AppState>,
+) -> Result<String, String> {
+    let (resolved_acp, agent_command, discovery) = {
+        let _store_guard = state
+            .managed_agents_store_lock
+            .lock()
+            .map_err(|e| e.to_string())?;
+        let records = load_managed_agents(&app)?;
+        let record = records
+            .iter()
+            .find(|r| r.pubkey == pubkey)
+            .ok_or_else(|| format!("agent {pubkey} not found"))?;
+
+        let resolved = resolve_command(&record.acp_command)
+            .ok_or_else(|| missing_command_message(&record.acp_command, "ACP harness command"))?;
+
+        let personas = load_personas(&app).unwrap_or_default();
+        let global = load_global_agent_config(&app).unwrap_or_default();
+        let discovery = agent_model_discovery_config(record, &personas, &global).map_err(|e| {
+            format!(
+                "cannot run completion for {pubkey}: {}",
+                user_facing_harness_error(&e)
+            )
+        })?;
+
+        let resolved_agent = resolve_command(&discovery.command)
+            .map(|p| p.display().to_string())
+            .unwrap_or_else(|| discovery.command.clone());
+
+        (resolved, resolved_agent, discovery)
+    }; // store lock released — subprocess runs without holding the lock
+
+    let AgentModelDiscoveryConfig {
+        command: descriptor_command,
+        args: agent_args,
+        model,
+        provider,
+        env: merged_env,
+        ..
+    } = discovery;
+    let mut merged_env = discovery_env_with_baked_floor(merged_env);
+
+    // Mirror spawn_agent_child: the harness reads model/provider from its
+    // runtime env vars, and those override the layered descriptor env.
+    if let Some(meta) = known_acp_runtime(&descriptor_command) {
+        for (key, value) in runtime_metadata_env_vars(
+            meta.model_env_var,
+            meta.provider_env_var,
+            meta.provider_locked,
+            model.as_deref(),
+            provider.as_deref(),
+        ) {
+            merged_env.insert(key.to_string(), value.to_string());
+        }
+    }
+
+    let mut helper_args = vec![
+        "complete".to_string(),
+        "--json".to_string(),
+        "--prompt".to_string(),
+        prompt,
+    ];
+    if let Some(system) = system_prompt.filter(|s| !s.trim().is_empty()) {
+        helper_args.push("--system-prompt".to_string());
+        helper_args.push(system);
+    }
+    if let Some(model) = model {
+        helper_args.push("--model".to_string());
+        helper_args.push(model);
+    }
+
+    let raw = run_acp_helper_subprocess(
+        resolved_acp,
+        agent_command,
+        agent_args,
+        merged_env,
+        helper_args,
+    )
+    .await?;
+
+    raw.get("text")
+        .and_then(|v| v.as_str())
+        .map(str::to_owned)
+        .ok_or_else(|| "buzz-acp complete returned no text".to_string())
+}
diff --git a/desktop/src-tauri/src/commands/agent_model_process.rs b/desktop/src-tauri/src/commands/agent_model_process.rs
index 998edeca27..f02115c386 100644
--- a/desktop/src-tauri/src/commands/agent_model_process.rs
+++ b/desktop/src-tauri/src/commands/agent_model_process.rs
@@ -7,21 +7,32 @@ use crate::managed_agents::{
 
 use super::agent_models::normalize_agent_models;
 
-pub(super) async fn run_agent_models_command(
+/// Run a lightweight `buzz-acp` helper subcommand (`models`, `complete`, ...)
+/// against the configured agent and parse its JSON stdout.
+///
+/// `helper_args` is the full subcommand argv (e.g. `["models", "--json"]`).
+/// Env layering mirrors runtime agent spawn: augmented PATH, runtime default
+/// env, baked provider defaults, then user env last so it always wins.
+pub(super) async fn run_acp_helper_subprocess(
     resolved_acp: PathBuf,
     agent_command: String,
     agent_args: Vec<String>,
-    persisted_model: Option<String>,
     merged_env: BTreeMap<String, String>,
-) -> Result<AgentModelsResponse, String> {
+    helper_args: Vec<String>,
+) -> Result<serde_json::Value, String> {
+    let subcommand = helper_args
+        .first()
+        .cloned()
+        .unwrap_or_else(|| "helper".into());
     // Clone the env map for redaction below — `merged_env` is moved
     // into the spawn_blocking closure and we still need the values to
     // scrub any user-supplied secrets that the child surfaces in stderr.
     let env_for_redaction = merged_env.clone();
+    let subcommand_in_closure = subcommand.clone();
 
     // Use spawn_blocking because the desktop Tauri crate doesn't enable
     // tokio's `process` feature. std::process::Command is synchronous
-    // but fine for a short-lived subprocess (~2-5s).
+    // but fine for a short-lived subprocess.
     let output = tokio::task::spawn_blocking(move || {
         let mut cmd = std::process::Command::new(&resolved_acp);
         if let Some(home) = default_agent_workdir() {
@@ -36,8 +47,7 @@ pub(super) async fn run_agent_models_command(
         if let Some(ref path) = crate::managed_agents::readiness::cli_probe::augmented_path() {
             cmd.env("PATH", path);
         }
-        cmd.arg("models")
-            .arg("--json")
+        cmd.args(&helper_args)
             .env("BUZZ_ACP_AGENT_COMMAND", &agent_command)
             .env("BUZZ_ACP_AGENT_ARGS", agent_args.join(","));
         if let Some(meta) = known_acp_runtime(&agent_command) {
@@ -59,10 +69,10 @@ pub(super) async fn run_agent_models_command(
         cmd.stdout(std::process::Stdio::piped())
             .stderr(std::process::Stdio::piped())
             .output()
-            .map_err(|e| format!("failed to spawn buzz-acp models: {e}"))
+            .map_err(|e| format!("failed to spawn buzz-acp {subcommand_in_closure}: {e}"))
     })
     .await
-    .map_err(|e| format!("model discovery task failed: {e}"))?
+    .map_err(|e| format!("buzz-acp {subcommand} task failed: {e}"))?
     .map_err(|e: String| e)?;
 
     if !output.status.success() {
@@ -72,13 +82,30 @@ pub(super) async fn run_agent_models_command(
         // a failing child process echoed back.
         let stderr_redacted = redact_env_values_in(stderr.as_ref(), &env_for_redaction);
         return Err(format!(
-            "buzz-acp models failed (exit {}): {stderr_redacted}",
+            "buzz-acp {subcommand} failed (exit {}): {stderr_redacted}",
             output.status.code().unwrap_or(-1)
         ));
     }
 
-    let raw: serde_json::Value = serde_json::from_slice(&output.stdout)
-        .map_err(|e| format!("failed to parse model JSON: {e}"))?;
+    serde_json::from_slice(&output.stdout)
+        .map_err(|e| format!("failed to parse buzz-acp {subcommand} JSON: {e}"))
+}
+
+pub(super) async fn run_agent_models_command(
+    resolved_acp: PathBuf,
+    agent_command: String,
+    agent_args: Vec<String>,
+    persisted_model: Option<String>,
+    merged_env: BTreeMap<String, String>,
+) -> Result<AgentModelsResponse, String> {
+    let raw = run_acp_helper_subprocess(
+        resolved_acp,
+        agent_command,
+        agent_args,
+        merged_env,
+        vec!["models".into(), "--json".into()],
+    )
+    .await?;
 
     Ok(normalize_agent_models(&raw, persisted_model))
 }
diff --git a/desktop/src-tauri/src/commands/agent_models.rs b/desktop/src-tauri/src/commands/agent_models.rs
index 7ce03b140b..d3cff9a215 100644
--- a/desktop/src-tauri/src/commands/agent_models.rs
+++ b/desktop/src-tauri/src/commands/agent_models.rs
@@ -167,9 +167,9 @@ fn model_discovery_error(pubkey: &str, error: &str) -> String {
 
 #[path = "agent_models_discovery_config.rs"]
 mod discovery_config;
-use discovery_config::{
-    agent_model_discovery_config, draft_agent_model_discovery_env, AgentModelDiscoveryConfig,
-};
+use discovery_config::draft_agent_model_discovery_env;
+// Re-exported for `agent_completion` (channel naming) to launch discovery.
+pub(super) use discovery_config::{agent_model_discovery_config, AgentModelDiscoveryConfig};
 
 #[derive(Debug, Deserialize)]
 #[serde(rename_all = "camelCase")]
diff --git a/desktop/src-tauri/src/commands/agent_models_discovery_config.rs b/desktop/src-tauri/src/commands/agent_models_discovery_config.rs
index e43f09495b..4bd5fe80ee 100644
--- a/desktop/src-tauri/src/commands/agent_models_discovery_config.rs
+++ b/desktop/src-tauri/src/commands/agent_models_discovery_config.rs
@@ -17,23 +17,23 @@ use crate::managed_agents::known_acp_runtime;
 /// one pure step so the linked-agent regression test can bind the exact values
 /// the command consumes.
 #[derive(Debug, PartialEq, Eq)]
-pub(super) struct AgentModelDiscoveryConfig {
+pub(in crate::commands) struct AgentModelDiscoveryConfig {
     /// Effective harness command (descriptor-resolved), for `resolve_command`.
-    pub(super) command: String,
+    pub(in crate::commands) command: String,
     /// Effective harness args (descriptor-resolved).
-    pub(super) args: Vec<String>,
+    pub(in crate::commands) args: Vec<String>,
     /// Model from the authoritative resolver spawn uses — linked instances
     /// read their definition, never stale `record.model` bytes.
-    pub(super) model: Option<String>,
+    pub(in crate::commands) model: Option<String>,
     /// Provider from the same authoritative resolver — never stale
     /// `record.provider` bytes for linked instances.
-    pub(super) provider: Option<String>,
+    pub(in crate::commands) provider: Option<String>,
     /// The runtime's provider env var (e.g. `GOOSE_PROVIDER`), so discovery
     /// can recover the provider from the env when the resolver yields none.
     /// `None` for runtimes that do not take a provider, or an unknown command.
-    pub(super) provider_env_var: Option<&'static str>,
+    pub(in crate::commands) provider_env_var: Option<&'static str>,
     /// The descriptor's fully layered env (definition/persona/global/agent).
-    pub(super) env: BTreeMap<String, String>,
+    pub(in crate::commands) env: BTreeMap<String, String>,
 }
 
 /// Resolve the model-discovery config for a saved agent — the descriptor-backed
@@ -55,7 +55,7 @@ pub(super) struct AgentModelDiscoveryConfig {
 /// Returns `Err("DANGLING_HARNESS_ID:<id>")` from the descriptor resolver when
 /// the harness id no longer exists; the caller routes it through
 /// `model_discovery_error`.
-pub(super) fn agent_model_discovery_config(
+pub(in crate::commands) fn agent_model_discovery_config(
     record: &crate::managed_agents::ManagedAgentRecord,
     personas: &[crate::managed_agents::AgentDefinition],
     global: &crate::managed_agents::GlobalAgentConfig,
diff --git a/desktop/src-tauri/src/commands/link_labels.rs b/desktop/src-tauri/src/commands/link_labels.rs
new file mode 100644
index 0000000000..d5e42cd3aa
--- /dev/null
+++ b/desktop/src-tauri/src/commands/link_labels.rs
@@ -0,0 +1,379 @@
+//! Rich link labels resolved through the locally installed `sq agent-tools`
+//! CLI. Slack permalinks sit behind an auth wall, and private Google files
+//! return "Sign in" pages, so plain HTML title fetching (link_preview.rs)
+//! can't label them. When the user has `sq` on their machine we ask the
+//! authenticated agent-tools extensions instead:
+//!
+//! - Slack channel message  → "author in #channel"
+//! - Slack DM message       → "author with partner"
+//! - Slack channel link     → "#channel"
+//! - Google Docs/Drive file → the file's real title
+//!
+//! Everything is best-effort: a missing `sq` binary, CLI errors, and
+//! timeouts all yield `Ok(None)` so the caller falls back to the generic
+//! page-title path.
+
+use std::path::PathBuf;
+use std::time::Duration;
+
+use serde_json::Value;
+use url::Url;
+
+const SQ_TIMEOUT: Duration = Duration::from_secs(20);
+
+#[derive(Debug, PartialEq)]
+enum AgentLink {
+    SlackMessage { channel: String, ts: String },
+    SlackChannel { channel: String },
+    GoogleFile,
+}
+
+#[tauri::command]
+pub async fn fetch_agent_link_label(href: String) -> Result<Option<String>, String> {
+    let url = Url::parse(href.trim()).map_err(|error| format!("invalid URL: {error}"))?;
+    let Some(link) = classify_agent_link(&url) else {
+        return Ok(None);
+    };
+    let Some(sq) = sq_binary() else {
+        return Ok(None);
+    };
+
+    let label = match link {
+        AgentLink::SlackMessage { channel, ts } => {
+            resolve_slack_message_label(&sq, &channel, &ts).await
+        }
+        AgentLink::SlackChannel { channel } => resolve_slack_conversation_label(&sq, &channel)
+            .await
+            .map(|conversation| conversation.label),
+        AgentLink::GoogleFile => resolve_google_file_label(&sq, url.as_str()).await,
+    };
+    Ok(label)
+}
+
+fn classify_agent_link(url: &Url) -> Option<AgentLink> {
+    if url.scheme() != "https" {
+        return None;
+    }
+    let host = url.host_str()?.to_ascii_lowercase();
+    let segments: Vec<&str> = url.path_segments()?.filter(|s| !s.is_empty()).collect();
+
+    if host == "slack.com" || host.ends_with(".slack.com") {
+        return match segments.as_slice() {
+            ["archives", channel] if looks_like_slack_conversation_id(channel) => {
+                Some(AgentLink::SlackChannel {
+                    channel: (*channel).to_string(),
+                })
+            }
+            ["archives", channel, message] if looks_like_slack_conversation_id(channel) => {
+                let ts = parse_slack_message_ts(message)?;
+                Some(AgentLink::SlackMessage {
+                    channel: (*channel).to_string(),
+                    ts,
+                })
+            }
+            _ => None,
+        };
+    }
+
+    super::is_supported_google_link(url).then_some(AgentLink::GoogleFile)
+}
+
+fn looks_like_slack_conversation_id(value: &str) -> bool {
+    let mut chars = value.chars();
+    matches!(chars.next(), Some('C' | 'D' | 'G'))
+        && value.len() >= 9
+        && chars.all(|c| c.is_ascii_alphanumeric())
+}
+
+/// Slack permalinks encode the message timestamp as `p1738012345123456`;
+/// the API wants `1738012345.123456`.
+fn parse_slack_message_ts(segment: &str) -> Option<String> {
+    let digits = segment.strip_prefix('p')?;
+    if digits.len() <= 10 || !digits.bytes().all(|b| b.is_ascii_digit()) {
+        return None;
+    }
+    let (seconds, fraction) = digits.split_at(10);
+    Some(format!("{seconds}.{fraction}"))
+}
+
+struct SlackConversation {
+    label: String,
+    is_dm: bool,
+}
+
+async fn resolve_slack_message_label(sq: &PathBuf, channel: &str, ts: &str) -> Option<String> {
+    let author_args = [
+        "agent-tools",
+        "slack",
+        "read-thread",
+        "--channel",
+        channel,
+        "--thread-ts",
+        ts,
+        "--limit",
+        "1",
+    ];
+    let author = run_sq_json(sq, &author_args);
+    let conversation = resolve_slack_conversation_label(sq, channel);
+    let (author, conversation) = tokio::join!(author, conversation);
+
+    let author = author.as_ref().and_then(extract_message_author)?;
+    let conversation = conversation?;
+    let joiner = if conversation.is_dm { "with" } else { "in" };
+    Some(format!("{author} {joiner} {}", conversation.label))
+}
+
+async fn resolve_slack_conversation_label(
+    sq: &PathBuf,
+    channel: &str,
+) -> Option<SlackConversation> {
+    if channel.starts_with('D') {
+        // resolve-name can't see DM conversation IDs, but search-channels
+        // matches them and returns the DM partner.
+        let result = run_sq_json(
+            sq,
+            &[
+                "agent-tools",
+                "slack",
+                "search-channels",
+                "--query",
+                channel,
+                "--limit",
+                "3",
+            ],
+        )
+        .await?;
+        let partner = extract_dm_partner(&result, channel)?;
+        return Some(SlackConversation {
+            label: partner,
+            is_dm: true,
+        });
+    }
+
+    let result = run_sq_json(
+        sq,
+        &[
+            "agent-tools",
+            "slack",
+            "resolve-name",
+            "--name",
+            channel,
+            "--entity-type",
+            "channel",
+        ],
+    )
+    .await?;
+    let name = result.get("name")?.as_str()?.trim();
+    if name.is_empty() || name == channel {
+        return None;
+    }
+    Some(SlackConversation {
+        label: format!("#{}", name.trim_start_matches('#')),
+        is_dm: result.get("type").and_then(Value::as_str) == Some("im"),
+    })
+}
+
+fn extract_message_author(result: &Value) -> Option<String> {
+    let user = result.get("messages")?.as_array()?.first()?.get("user")?;
+    let author = user
+        .get("username")
+        .and_then(Value::as_str)
+        .filter(|name| !name.trim().is_empty())
+        .or_else(|| {
+            user.get("real_name")
+                .and_then(Value::as_str)
+                .filter(|name| !name.trim().is_empty())
+        })?;
+    Some(author.trim().to_string())
+}
+
+fn extract_dm_partner(result: &Value, channel: &str) -> Option<String> {
+    let results = result.get("results")?.as_array()?;
+    let dm = results
+        .iter()
+        .find(|entry| entry.get("id").and_then(Value::as_str) == Some(channel))?;
+    let partner = dm.get("dm_user")?;
+    let name = partner
+        .get("username")
+        .and_then(Value::as_str)
+        .filter(|name| !name.trim().is_empty())
+        .or_else(|| {
+            partner
+                .get("real_name")
+                .and_then(Value::as_str)
+                .filter(|name| !name.trim().is_empty())
+        })?;
+    Some(name.trim().to_string())
+}
+
+async fn resolve_google_file_label(sq: &PathBuf, href: &str) -> Option<String> {
+    let result = run_sq_json(
+        sq,
+        &[
+            "agent-tools",
+            "google-drive",
+            "get-file-metadata",
+            "--file-id-or-url",
+            href,
+        ],
+    )
+    .await?;
+    let name = result.get("file")?.get("name")?.as_str()?.trim();
+    (!name.is_empty()).then(|| name.chars().take(180).collect())
+}
+
+fn sq_binary() -> Option<PathBuf> {
+    crate::managed_agents::resolve_command("sq")
+}
+
+async fn run_sq_json(sq: &PathBuf, args: &[&str]) -> Option<Value> {
+    let mut command = tokio::process::Command::new(sq);
+    command
+        .args(args)
+        .stdin(std::process::Stdio::null())
+        .stdout(std::process::Stdio::piped())
+        .stderr(std::process::Stdio::null())
+        .kill_on_drop(true);
+    #[cfg(windows)]
+    {
+        use std::os::windows::process::CommandExt;
+        command.creation_flags(0x0800_0000); // CREATE_NO_WINDOW
+    }
+
+    let output = tokio::time::timeout(SQ_TIMEOUT, command.output())
+        .await
+        .ok()?
+        .ok()?;
+    if !output.status.success() {
+        return None;
+    }
+    serde_json::from_slice(&output.stdout).ok()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{
+        classify_agent_link, extract_dm_partner, extract_message_author, parse_slack_message_ts,
+        AgentLink,
+    };
+    use serde_json::json;
+    use url::Url;
+
+    fn classify(href: &str) -> Option<AgentLink> {
+        classify_agent_link(&Url::parse(href).unwrap())
+    }
+
+    #[test]
+    fn slack_message_permalinks_classify_with_api_ts() {
+        assert_eq!(
+            classify("https://block.slack.com/archives/C0AJ54K0KNY/p1785361516443929"),
+            Some(AgentLink::SlackMessage {
+                channel: "C0AJ54K0KNY".to_string(),
+                ts: "1785361516.443929".to_string(),
+            })
+        );
+        // Thread-reply permalinks carry a query string; the p-segment is
+        // still the linked message.
+        assert_eq!(
+            classify(
+                "https://block.slack.com/archives/D0BLPGME058/p1785367578361779?thread_ts=1785361516.443929&cid=D0BLPGME058"
+            ),
+            Some(AgentLink::SlackMessage {
+                channel: "D0BLPGME058".to_string(),
+                ts: "1785367578.361779".to_string(),
+            })
+        );
+    }
+
+    #[test]
+    fn slack_channel_links_classify_without_ts() {
+        assert_eq!(
+            classify("https://block.slack.com/archives/C0AJ54K0KNY"),
+            Some(AgentLink::SlackChannel {
+                channel: "C0AJ54K0KNY".to_string(),
+            })
+        );
+    }
+
+    #[test]
+    fn non_archive_and_non_slack_urls_do_not_classify_as_slack() {
+        assert_eq!(classify("https://block.slack.com/team/U123456"), None);
+        assert_eq!(
+            classify("https://notslack.com/archives/C0AJ54K0KNY/p1785361516443929"),
+            None
+        );
+        assert_eq!(
+            classify("http://block.slack.com/archives/C0AJ54K0KNY"),
+            None
+        );
+        // Malformed p-segments fall through entirely.
+        assert_eq!(
+            classify("https://block.slack.com/archives/C0AJ54K0KNY/p123"),
+            None
+        );
+        assert_eq!(
+            classify("https://block.slack.com/archives/general/p1785361516443929"),
+            None
+        );
+    }
+
+    #[test]
+    fn google_file_links_classify() {
+        assert_eq!(
+            classify("https://docs.google.com/document/d/1WQchQDNfF6ZD/edit"),
+            Some(AgentLink::GoogleFile)
+        );
+        assert_eq!(
+            classify("https://drive.google.com/file/d/abc123/view"),
+            Some(AgentLink::GoogleFile)
+        );
+        assert_eq!(classify("https://docs.google.com/"), None);
+    }
+
+    #[test]
+    fn permalink_ts_requires_p_prefix_and_digits() {
+        assert_eq!(
+            parse_slack_message_ts("p1785361516443929").as_deref(),
+            Some("1785361516.443929")
+        );
+        assert_eq!(parse_slack_message_ts("1785361516443929"), None);
+        assert_eq!(parse_slack_message_ts("p1785361516"), None);
+        assert_eq!(parse_slack_message_ts("p17853615164439x9"), None);
+    }
+
+    #[test]
+    fn author_prefers_username_then_real_name() {
+        let with_username = json!({
+            "messages": [{ "user": { "username": "gpap", "real_name": "Gábor Pap" } }]
+        });
+        assert_eq!(
+            extract_message_author(&with_username).as_deref(),
+            Some("gpap")
+        );
+
+        let real_name_only = json!({
+            "messages": [{ "user": { "username": "", "real_name": "Gábor Pap" } }]
+        });
+        assert_eq!(
+            extract_message_author(&real_name_only).as_deref(),
+            Some("Gábor Pap")
+        );
+
+        assert_eq!(extract_message_author(&json!({ "messages": [] })), None);
+    }
+
+    #[test]
+    fn dm_partner_matches_conversation_id_exactly() {
+        let result = json!({
+            "results": [
+                { "id": "D0OTHER", "dm_user": { "username": "wrong" } },
+                { "id": "D0BLPGME058", "dm_user": { "username": "dreya", "real_name": "Dreya Griffin" } }
+            ]
+        });
+        assert_eq!(
+            extract_dm_partner(&result, "D0BLPGME058").as_deref(),
+            Some("dreya")
+        );
+        assert_eq!(extract_dm_partner(&result, "D0MISSING"), None);
+    }
+}
diff --git a/desktop/src-tauri/src/commands/link_preview.rs b/desktop/src-tauri/src/commands/link_preview.rs
index 5cc9c01d33..d1c8f7b5e3 100644
--- a/desktop/src-tauri/src/commands/link_preview.rs
+++ b/desktop/src-tauri/src/commands/link_preview.rs
@@ -55,7 +55,74 @@ pub async fn fetch_link_preview_title(href: String) -> Result<Option<String>, St
     Ok(extract_google_title(&body))
 }
 
-fn is_supported_google_link(url: &Url) -> bool {
+/// Fetch the page title of any https URL — og:title / twitter:title falling
+/// back to `<title>`. Best-effort: auth walls, non-HTML responses, and
+/// timeouts all yield `Ok(None)` so callers can render the bare link.
+#[tauri::command]
+pub async fn fetch_page_title(href: String) -> Result<Option<String>, String> {
+    let url = Url::parse(href.trim()).map_err(|error| format!("invalid URL: {error}"))?;
+    if url.scheme() != "https" {
+        return Ok(None);
+    }
+
+    let client = reqwest::Client::builder()
+        .redirect(Policy::limited(3))
+        .pool_idle_timeout(Duration::from_secs(10))
+        .pool_max_idle_per_host(1)
+        .build()
+        .map_err(|error| format!("page title client failed: {error}"))?;
+
+    let request = client
+        .get(url.as_str())
+        .header(
+            ACCEPT,
+            "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
+        )
+        .header(USER_AGENT, "Buzz Desktop link preview");
+
+    let response = match tokio::time::timeout(TITLE_FETCH_TIMEOUT, request.send()).await {
+        Ok(Ok(response)) => response,
+        Ok(Err(_)) | Err(_) => return Ok(None),
+    };
+
+    if !response.status().is_success() {
+        return Ok(None);
+    }
+
+    let is_html = response
+        .headers()
+        .get(CONTENT_TYPE)
+        .and_then(|value| value.to_str().ok())
+        .map(|value| value.to_ascii_lowercase().contains("text/html"))
+        .unwrap_or(true);
+    if !is_html {
+        return Ok(None);
+    }
+
+    let body = read_limited_text(response).await?;
+    Ok(extract_page_title(&body))
+}
+
+fn extract_page_title(html: &str) -> Option<String> {
+    let raw = extract_meta_title(html).or_else(|| extract_title_tag(html))?;
+    let title = decode_html_entities(&raw)
+        .split_whitespace()
+        .collect::<Vec<_>>()
+        .join(" ");
+    if title.is_empty() || is_auth_wall_title(&title) {
+        return None;
+    }
+    Some(title)
+}
+
+/// Auth walls (Slack, Google, Okta, ...) title their login pages "Sign in
+/// ..." — worse than useless as a link label, so render the bare URL instead.
+fn is_auth_wall_title(title: &str) -> bool {
+    let lower = title.to_ascii_lowercase();
+    lower.starts_with("sign in") || lower.starts_with("log in") || lower.starts_with("login")
+}
+
+pub(crate) fn is_supported_google_link(url: &Url) -> bool {
     if url.scheme() != "https" {
         return false;
     }
@@ -251,9 +318,52 @@ fn decode_html_entities(value: &str) -> String {
 
 #[cfg(test)]
 mod tests {
-    use super::{extract_google_title, is_supported_google_link};
+    use super::{extract_google_title, extract_page_title, is_supported_google_link};
     use url::Url;
 
+    #[test]
+    fn page_title_prefers_open_graph_then_title_tag() {
+        let html = r#"
+          <html>
+            <head>
+              <meta property="og:title" content="Slack thread &amp; replies">
+              <title>Fallback title</title>
+            </head>
+          </html>
+        "#;
+        assert_eq!(
+            extract_page_title(html).as_deref(),
+            Some("Slack thread & replies")
+        );
+        assert_eq!(
+            extract_page_title("<title>Plain\n  Page   Title</title>").as_deref(),
+            Some("Plain Page Title")
+        );
+    }
+
+    #[test]
+    fn page_title_none_when_absent_or_blank() {
+        assert_eq!(
+            extract_page_title("<html><body>no title</body></html>"),
+            None
+        );
+        assert_eq!(extract_page_title("<title>   </title>"), None);
+    }
+
+    #[test]
+    fn page_title_rejects_auth_wall_titles() {
+        assert_eq!(extract_page_title("<title>Sign in to Block</title>"), None);
+        assert_eq!(
+            extract_page_title("<title>Log in | Workspace</title>"),
+            None
+        );
+        assert_eq!(extract_page_title("<title>LOGIN</title>"), None);
+        assert_eq!(
+            extract_page_title("<title>Design signals</title>").as_deref(),
+            Some("Design signals")
+        );
+    }
+
     #[test]
     fn title_prefers_open_graph_title() {
         let html = r#"
diff --git a/desktop/src-tauri/src/commands/mod.rs b/desktop/src-tauri/src/commands/mod.rs
index 66ef7ef17b..ef8b7efbbe 100644
--- a/desktop/src-tauri/src/commands/mod.rs
+++ b/desktop/src-tauri/src/commands/mod.rs
@@ -1,4 +1,5 @@
 mod agent_auth;
+mod agent_completion;
 mod agent_config;
 mod agent_discovery;
 mod agent_logs;
@@ -23,6 +24,7 @@ mod identity;
 mod identity_archive;
 mod join_policy;
 mod legacy_storage;
+mod link_labels;
 mod link_preview;
 pub(crate) mod media;
 mod media_animated;
@@ -62,6 +64,7 @@ mod workflows;
 mod workspace;
 
 pub use agent_auth::*;
+pub use agent_completion::*;
 pub use agent_config::*;
 pub use agent_discovery::*;
 pub use agent_logs::*;
@@ -82,6 +85,7 @@ pub use identity::*;
 pub use identity_archive::*;
 pub use join_policy::*;
 pub use legacy_storage::*;
+pub use link_labels::*;
 pub use link_preview::*;
 pub use media::*;
 pub use media_download::*;
diff --git a/desktop/src-tauri/src/lib.rs b/desktop/src-tauri/src/lib.rs
index 35f4eae866..5fc5c3545a 100644
--- a/desktop/src-tauri/src/lib.rs
+++ b/desktop/src-tauri/src/lib.rs
@@ -693,7 +693,9 @@ pub fn run() {
             get_relay_ws_url,
             get_relay_http_url,
             get_media_proxy_port,
+            fetch_agent_link_label,
             fetch_link_preview_title,
+            fetch_page_title,
             discover_acp_auth_methods,
             discover_acp_providers,
             discover_git_bash_prerequisite,
@@ -786,6 +788,7 @@ pub fn run() {
             get_managed_agent_log,
             get_agent_models,
             discover_agent_models,
+            generate_agent_completion,
             get_agent_config_surface,
             get_runtime_file_config,
             get_baked_build_env_keys,
diff --git a/desktop/src/app/AppShell.tsx b/desktop/src/app/AppShell.tsx
index abbbf29610..c47adea0c8 100644
--- a/desktop/src/app/AppShell.tsx
+++ b/desktop/src/app/AppShell.tsx
@@ -13,6 +13,7 @@ import { useLiveHomeFeedActions } from "@/app/useLiveHomeFeedActions";
 import { useChannelBrowserDialog } from "@/app/useChannelBrowserDialog";
 import { useMarkAsReadShortcuts } from "@/app/useMarkAsReadShortcuts";
 import { useSettingsShortcuts } from "@/app/useSettingsShortcuts";
+import { useGlobalActionShortcuts } from "@/app/useGlobalActionShortcuts";
 import { useAppShellDesktopNotifications } from "@/app/useAppShellDesktopNotifications";
 import { useAppShellLifecycleEffects } from "@/app/useAppShellLifecycleEffects";
 import { useThreadActivityFeedItems } from "@/app/useThreadActivityFeedItems";
@@ -80,6 +81,7 @@ import {
 } from "@/features/communities/communityNavigationStorage";
 import { useAddCommunityDialogState } from "@/features/communities/addCommunityPrefill";
 import { useApplyTemplate } from "@/features/channel-templates/useApplyTemplate";
+import { useDisplayStyle } from "@/features/dev-mode/lib/displayStylePreference";
 import { relayClient } from "@/shared/api/relayClient";
 import { useIdentityQuery } from "@/shared/api/hooks";
 import { useRelayAutoHeal } from "@/shared/api/useRelayAutoHeal";
@@ -91,7 +93,6 @@ import { ChannelNavigationProvider } from "@/shared/context/ChannelNavigationCon
 import { MainInsetProvider } from "@/shared/layout/MainInsetContext";
 import { chromeCssVarDefaults } from "@/shared/layout/chromeLayout";
 import { cn } from "@/shared/lib/cn";
-import { hasPrimaryShortcutModifier } from "@/shared/lib/platform";
 import { useMessageDeepLinks } from "@/shared/useMessageDeepLinks";
 import { SidebarInset, SidebarProvider } from "@/shared/ui/sidebar";
 import { RelayConnectionOverlay } from "@/app/RelayConnectionOverlay";
@@ -102,10 +103,16 @@ const LazySettingsScreen = React.lazy(async () => {
   return { default: module.SettingsScreen };
 });
 
+const LazyDevModeShell = React.lazy(async () => {
+  const module = await import("@/features/dev-mode/ui/DevModeShell");
+  return { default: module.DevModeShell };
+});
+
 export function AppShell() {
   useWebviewZoomShortcuts();
   useTauriWindowDrag();
   useWebviewScrollBoundaryLock();
+  const displayStyle = useDisplayStyle();
   const communitiesHook = useCommunities();
   const hasCommunityRail = communitiesHook.communities.length > 1;
   const addCommunityDialog = useAddCommunityDialogState();
@@ -328,6 +335,7 @@ export function AppShell() {
     markChannelRead,
     markChannelUnread,
     unreadChannelIds,
+    topLevelUnreadChannelIds,
     unreadChannelCounts,
     highPriorityUnreadChannelIds,
     unreadChannelNotificationCount,
@@ -632,69 +640,15 @@ export function AppShell() {
     () => setIsCreateChannelOpen(true),
     [],
   );
-  React.useLayoutEffect(() => {
-    if (settingsOpen) {
-      return;
-    }
-
-    function handleKeyDown(event: KeyboardEvent) {
-      if (!hasPrimaryShortcutModifier(event) || event.altKey || event.repeat) {
-        return;
-      }
-
-      // A focused surface may claim the shortcut first — e.g. the composer
-      // consumes ⌘K to open the link editor when text is selected. Its
-      // element-level handler runs before this window-level bubble listener
-      // and calls `preventDefault()`; respect that instead of also opening
-      // the global dialog.
-      if (event.defaultPrevented) {
-        return;
-      }
-
-      const key = event.key.toLowerCase();
-      if (key === "k" && !event.shiftKey) {
-        event.preventDefault();
-        handleOpenSearch();
-        return;
-      }
-
-      if (key === "k" && event.shiftKey) {
-        event.preventDefault();
-        handleOpenNewDm();
-        return;
-      }
-
-      if (key === "n" && event.shiftKey) {
-        event.preventDefault();
-        handleOpenCreateChannel();
-        return;
-      }
-
-      if (key === "o" && event.shiftKey) {
-        event.preventDefault();
-        handleOpenBrowseChannels();
-        return;
-      }
-
-      if (key === "a" && event.shiftKey) {
-        event.preventDefault();
-        void goHome();
-        return;
-      }
-    }
-
-    window.addEventListener("keydown", handleKeyDown);
-    return () => {
-      window.removeEventListener("keydown", handleKeyDown);
-    };
-  }, [
-    handleOpenBrowseChannels,
-    handleOpenNewDm,
-    handleOpenCreateChannel,
-    handleOpenSearch,
-    goHome,
+  const handleGoHomeShortcut = React.useCallback(() => void goHome(), [goHome]);
+  useGlobalActionShortcuts({
     settingsOpen,
-  ]);
+    onOpenSearch: handleOpenSearch,
+    onOpenNewDm: handleOpenNewDm,
+    onOpenCreateChannel: handleOpenCreateChannel,
+    onOpenBrowseChannels: handleOpenBrowseChannels,
+    onGoHome: handleGoHomeShortcut,
+  });
   useSettingsShortcuts({
     onClose: handleCloseSettings,
     onOpenSettings: handleOpenSettings,
@@ -766,10 +720,15 @@ export function AppShell() {
                       onSwitchCommunity={handleSwitchCommunity}
                       onUpdateCommunity={communitiesHook.updateCommunity}
                       communities={communitiesHook.communities}
+                      variant={
+                        !settingsOpen && displayStyle === "developer"
+                          ? "developer"
+                          : "standard"
+                      }
                     />
                   ) : null}
                   <SidebarProvider className="min-h-0 flex-1 flex-col overflow-hidden">
-                    {!settingsOpen ? (
+                    {!settingsOpen && displayStyle !== "developer" ? (
                       <AppTopChrome
                         canGoBack={canGoBack}
                         canGoForward={canGoForward}
@@ -820,6 +779,16 @@ export function AppShell() {
                           />
                         </React.Suspense>
                       </div>
+                    ) : displayStyle === "developer" ? (
+                      <div className="flex min-h-0 flex-1 overflow-hidden">
+                        <React.Suspense fallback={null}>
+                          <LazyDevModeShell
+                            hasCommunityRail={hasCommunityRail}
+                            topLevelUnreadChannelIds={topLevelUnreadChannelIds}
+                            unreadChannelIds={unreadChannelIds}
+                          />
+                        </React.Suspense>
+                      </div>
                     ) : (
                       <div className="flex min-h-0 flex-1 overflow-hidden">
                         <AppSidebar
diff --git a/desktop/src/app/useGlobalActionShortcuts.ts b/desktop/src/app/useGlobalActionShortcuts.ts
new file mode 100644
index 0000000000..8984a80e04
--- /dev/null
+++ b/desktop/src/app/useGlobalActionShortcuts.ts
@@ -0,0 +1,95 @@
+import * as React from "react";
+
+import { toggleDisplayStyle } from "@/features/dev-mode/lib/displayStylePreference";
+import { hasPrimaryShortcutModifier } from "@/shared/lib/platform";
+
+/**
+ * Window-level primary-modifier shortcuts: ⌘K search, ⇧⌘K new DM, ⇧⌘N create
+ * channel, ⇧⌘O browse channels, ⇧⌘A home, ⇧⌘D display style. Disabled while
+ * settings is open (settings has its own shortcut scope).
+ */
+export function useGlobalActionShortcuts({
+  settingsOpen,
+  onOpenSearch,
+  onOpenNewDm,
+  onOpenCreateChannel,
+  onOpenBrowseChannels,
+  onGoHome,
+}: {
+  settingsOpen: boolean;
+  onOpenSearch: () => void;
+  onOpenNewDm: () => void;
+  onOpenCreateChannel: () => void;
+  onOpenBrowseChannels: () => void;
+  onGoHome: () => void;
+}) {
+  React.useLayoutEffect(() => {
+    if (settingsOpen) {
+      return;
+    }
+
+    function handleKeyDown(event: KeyboardEvent) {
+      if (!hasPrimaryShortcutModifier(event) || event.altKey || event.repeat) {
+        return;
+      }
+
+      // A focused surface may claim the shortcut first — e.g. the composer
+      // consumes ⌘K to open the link editor when text is selected. Its
+      // element-level handler runs before this window-level bubble listener
+      // and calls `preventDefault()`; respect that instead of also opening
+      // the global dialog.
+      if (event.defaultPrevented) {
+        return;
+      }
+
+      const key = event.key.toLowerCase();
+      if (key === "k" && !event.shiftKey) {
+        event.preventDefault();
+        onOpenSearch();
+        return;
+      }
+
+      if (key === "k" && event.shiftKey) {
+        event.preventDefault();
+        onOpenNewDm();
+        return;
+      }
+
+      if (key === "n" && event.shiftKey) {
+        event.preventDefault();
+        onOpenCreateChannel();
+        return;
+      }
+
+      if (key === "o" && event.shiftKey) {
+        event.preventDefault();
+        onOpenBrowseChannels();
+        return;
+      }
+
+      if (key === "a" && event.shiftKey) {
+        event.preventDefault();
+        onGoHome();
+        return;
+      }
+
+      if (key === "d" && event.shiftKey) {
+        event.preventDefault();
+        toggleDisplayStyle();
+        return;
+      }
+    }
+
+    window.addEventListener("keydown", handleKeyDown);
+    return () => {
+      window.removeEventListener("keydown", handleKeyDown);
+    };
+  }, [
+    settingsOpen,
+    onOpenSearch,
+    onOpenNewDm,
+    onOpenCreateChannel,
+    onOpenBrowseChannels,
+    onGoHome,
+  ]);
+}
diff --git a/desktop/src/features/channels/hooks.ts b/desktop/src/features/channels/hooks.ts
index 9003d0f5a5..626c7ddef1 100644
--- a/desktop/src/features/channels/hooks.ts
+++ b/desktop/src/features/channels/hooks.ts
@@ -36,6 +36,10 @@ import {
   readChannelSnapshot,
   writeChannelSnapshot,
 } from "@/features/channels/channelSnapshot";
+import {
+  applySubChannelRenames,
+  planSubChannelRenames,
+} from "@/features/dev-mode/lib/subChannels";
 
 export const channelsQueryKey = ["channels"] as const;
 const channelDetailQueryKey = (channelId: string) =>
@@ -187,6 +191,62 @@ function setChannelArchivedState(
   );
 }
 
+/**
+ * Patch one channel in the list + detail caches. Used for optimistic
+ * membership updates so join/leave/add/archive feel instant; the settle-time
+ * invalidate reconciles with the relay's answer.
+ */
+function patchChannelState(
+  queryClient: ReturnType<typeof useQueryClient>,
+  channelId: string,
+  patch: (channel: Channel) => Channel,
+) {
+  queryClient.setQueryData<Channel[]>(channelsQueryKey, (current = []) =>
+    sortChannels(
+      current.map((channel) =>
+        channel.id === channelId ? patch(channel) : channel,
+      ),
+    ),
+  );
+
+  queryClient.setQueryData<ChannelDetail | undefined>(
+    channelDetailQueryKey(channelId),
+    (current) => (current ? { ...current, ...patch(current) } : current),
+  );
+}
+
+/**
+ * Snapshot the caches an optimistic channel patch touches, for onError
+ * rollback. Restoring the full list is simpler and safer than un-applying
+ * the patch.
+ */
+function snapshotChannelState(
+  queryClient: ReturnType<typeof useQueryClient>,
+  channelId: string,
+) {
+  return {
+    channels: queryClient.getQueryData<Channel[]>(channelsQueryKey),
+    detail: queryClient.getQueryData<ChannelDetail | undefined>(
+      channelDetailQueryKey(channelId),
+    ),
+  };
+}
+
+function restoreChannelState(
+  queryClient: ReturnType<typeof useQueryClient>,
+  channelId: string,
+  snapshot: ReturnType<typeof snapshotChannelState> | undefined,
+) {
+  if (!snapshot) return;
+  if (snapshot.channels) {
+    queryClient.setQueryData<Channel[]>(channelsQueryKey, snapshot.channels);
+  }
+  queryClient.setQueryData<ChannelDetail | undefined>(
+    channelDetailQueryKey(channelId),
+    snapshot.detail,
+  );
+}
+
 export function useChannelsQuery(options?: { enabled?: boolean }) {
   const { activeCommunity } = useCommunities();
   const relayUrl = activeCommunity?.relayUrl ?? null;
@@ -341,12 +401,41 @@ export function useUpdateChannelMutation(channelId: string | null) {
   const queryClient = useQueryClient();
 
   return useMutation({
-    mutationFn: (input: Omit<UpdateChannelInput, "channelId">) => {
+    mutationFn: async (input: Omit<UpdateChannelInput, "channelId">) => {
       if (!channelId) {
         throw new Error("No channel selected.");
       }
 
-      return updateChannel({ ...input, channelId });
+      const previousName = queryClient
+        .getQueryData<Channel[]>(channelsQueryKey)
+        ?.find((channel) => channel.id === channelId)?.name;
+      const updated = await updateChannel({ ...input, channelId });
+
+      // A `parent--sub` channel is linked to its parent purely by name, so
+      // renaming a parent must rename every sub or the family falls apart.
+      // Best-effort, bounded concurrency — a parent can have hundreds.
+      if (previousName && previousName !== updated.name) {
+        const plan = planSubChannelRenames(
+          queryClient.getQueryData<Channel[]>(channelsQueryKey) ?? [],
+          previousName,
+          updated.name,
+        );
+        if (plan.length > 0) {
+          const { failed } = await applySubChannelRenames(
+            plan,
+            async (subChannelId, newName) => {
+              await updateChannel({ channelId: subChannelId, name: newName });
+            },
+          );
+          if (failed.length > 0) {
+            console.warn(
+              `channel rename: ${failed.length} of ${plan.length} sub-channel(s) failed to follow "${previousName}" → "${updated.name}"`,
+            );
+          }
+        }
+      }
+
+      return updated;
     },
     onMutate: () => ({ channelId }),
     onSuccess: (updatedChannel) => {
@@ -427,12 +516,15 @@ export function useArchiveChannelMutation(channelId: string | null) {
 
       await archiveChannel(channelId);
     },
-    onSuccess: () => {
-      if (!channelId) {
-        return;
-      }
-
+    onMutate: () => {
+      if (!channelId) return undefined;
+      const snapshot = snapshotChannelState(queryClient, channelId);
       setChannelArchivedState(queryClient, channelId, new Date().toISOString());
+      return snapshot;
+    },
+    onError: (_error, _variables, snapshot) => {
+      if (!channelId) return;
+      restoreChannelState(queryClient, channelId, snapshot);
     },
     onSettled: async () => {
       await invalidateChannelState(queryClient, channelId);
@@ -517,6 +609,22 @@ export function useAddChannelMembersMutation(channelId: string | null) {
 
       return addChannelMembers({ ...rest, channelId: effectiveChannelId });
     },
+    onMutate: (variables) => {
+      const effectiveChannelId = variables?.channelId ?? channelId;
+      if (!effectiveChannelId) return undefined;
+      const snapshot = snapshotChannelState(queryClient, effectiveChannelId);
+      const added = variables.pubkeys.length;
+      patchChannelState(queryClient, effectiveChannelId, (channel) => ({
+        ...channel,
+        memberCount: channel.memberCount + added,
+      }));
+      return snapshot;
+    },
+    onError: (_error, variables, snapshot) => {
+      const effectiveChannelId = variables?.channelId ?? channelId;
+      if (!effectiveChannelId) return;
+      restoreChannelState(queryClient, effectiveChannelId, snapshot);
+    },
     onSettled: async (_data, _err, variables) => {
       // Invalidate the effective channel (the one actually mutated) not the
       // live hook-closure channel, which may have changed mid-send.
@@ -551,15 +659,38 @@ export function useJoinChannelMutation(channelId: string | null) {
   const queryClient = useQueryClient();
 
   return useMutation({
-    mutationFn: async () => {
-      if (!channelId) {
+    // Accepts a per-call channel override so one hook instance can join
+    // arbitrary channels (e.g. palette search results).
+    // biome-ignore lint/suspicious/noConfusingVoidType: `| void` (not `| undefined`) is what lets existing no-arg `mutate()` callers compile.
+    mutationFn: async (variables: { channelId?: string } | void) => {
+      const effectiveChannelId = variables?.channelId ?? channelId;
+      if (!effectiveChannelId) {
         throw new Error("No channel selected.");
       }
 
-      await joinChannel(channelId);
+      await joinChannel(effectiveChannelId);
     },
-    onSettled: async () => {
-      await invalidateChannelState(queryClient, channelId);
+    onMutate: (variables) => {
+      const effectiveChannelId = variables?.channelId ?? channelId;
+      if (!effectiveChannelId) return undefined;
+      const snapshot = snapshotChannelState(queryClient, effectiveChannelId);
+      patchChannelState(queryClient, effectiveChannelId, (channel) => ({
+        ...channel,
+        isMember: true,
+        memberCount: channel.memberCount + 1,
+      }));
+      return snapshot;
+    },
+    onError: (_error, variables, snapshot) => {
+      const effectiveChannelId = variables?.channelId ?? channelId;
+      if (!effectiveChannelId) return;
+      restoreChannelState(queryClient, effectiveChannelId, snapshot);
+    },
+    onSettled: async (_data, _error, variables) => {
+      await invalidateChannelState(
+        queryClient,
+        variables?.channelId ?? channelId,
+      );
     },
   });
 }
@@ -575,6 +706,20 @@ export function useLeaveChannelMutation(channelId: string | null) {
 
       await leaveChannel(channelId);
     },
+    onMutate: () => {
+      if (!channelId) return undefined;
+      const snapshot = snapshotChannelState(queryClient, channelId);
+      patchChannelState(queryClient, channelId, (channel) => ({
+        ...channel,
+        isMember: false,
+        memberCount: Math.max(0, channel.memberCount - 1),
+      }));
+      return snapshot;
+    },
+    onError: (_error, _variables, snapshot) => {
+      if (!channelId) return;
+      restoreChannelState(queryClient, channelId, snapshot);
+    },
     onSettled: async () => {
       await invalidateChannelState(queryClient, channelId);
     },
diff --git a/desktop/src/features/channels/unreadChannelCounts.ts b/desktop/src/features/channels/unreadChannelCounts.ts
index cb33c62975..274af64b38 100644
--- a/desktop/src/features/channels/unreadChannelCounts.ts
+++ b/desktop/src/features/channels/unreadChannelCounts.ts
@@ -106,6 +106,25 @@ export function countUnreadAppBadgeObservedEvents(
   return count;
 }
 
+/**
+ * Unread channel-level posts only (rootId === null) — thread replies never
+ * count. Dev mode's channel list uses this so a channel reads as unread only
+ * when a top-level message is unread, not when unopened threads have replies.
+ */
+export function countUnreadTopLevelObservedEvents(
+  eventsById: ReadonlyMap<string, ObservedUnreadEvent> | undefined,
+  getReadAt: (event: ObservedUnreadEvent) => number | null,
+): number {
+  if (!eventsById) return 0;
+  let count = 0;
+  for (const event of eventsById.values()) {
+    if (event.rootId !== null) continue;
+    const readAt = getReadAt(event);
+    if (readAt === null || event.createdAt > readAt) count += 1;
+  }
+  return count;
+}
+
 export function countUnreadHighPriorityObservedEvents(
   eventsById: ReadonlyMap<string, ObservedUnreadEvent> | undefined,
   getReadAt: (event: ObservedUnreadEvent) => number | null,
diff --git a/desktop/src/features/channels/unreadReadMarker.test.mjs b/desktop/src/features/channels/unreadReadMarker.test.mjs
index e05e2ba0b2..fb09b0fb12 100644
--- a/desktop/src/features/channels/unreadReadMarker.test.mjs
+++ b/desktop/src/features/channels/unreadReadMarker.test.mjs
@@ -7,15 +7,16 @@ import {
   countUnreadBadgeObservedEvents,
   countUnreadHighPriorityObservedEvents,
   countUnreadObservedEvents,
+  countUnreadTopLevelObservedEvents,
   observedUnreadEventReadAt,
   recordObservedUnreadEvent,
 } from "./unreadChannelCounts.ts";
+import { addThreadActivityItems } from "./useUnreadChannels.ts";
 import {
-  addThreadActivityItems,
   channelCatchUpEventKinds,
   resolveChannelReadMarker,
   resolveObservedUnreadRootId,
-} from "./useUnreadChannels.ts";
+} from "./unreadReadMarker.ts";
 import {
   isChannelUnreadTriggerKind,
   withChannelTagFallback,
@@ -333,6 +334,38 @@ test("sidebarPipeline_openedReplyMessageMarkerClearsDelayedReplay", () => {
   );
 });
 
+test("countUnreadTopLevelObservedEvents_ignoresThreadReplies", () => {
+  // Channel marker covers the newest top-level post (300). Two thread replies
+  // are strictly newer and unread, but a dev-mode channel dot only tracks
+  // channel-level posts, so the top-level count must be zero.
+  const events = new Map([
+    ["reply-a", observed("reply-a", 400, "root-a")],
+    ["reply-b", observed("reply-b", 500, "root-b")],
+  ]);
+  const getReadAt = readAtFor(300, new Map());
+
+  assert.equal(countUnreadObservedEvents(events, getReadAt), 2);
+  assert.equal(countUnreadTopLevelObservedEvents(events, getReadAt), 0);
+});
+
+test("countUnreadTopLevelObservedEvents_countsUnreadChannelLevelPosts", () => {
+  const events = new Map([
+    ["post", observed("post", 400, null)],
+    ["reply", observed("reply", 500, "root-a")],
+  ]);
+
+  // Marker behind the top-level post: it counts; the newer reply never does.
+  assert.equal(
+    countUnreadTopLevelObservedEvents(events, readAtFor(300, new Map())),
+    1,
+  );
+  // Marker at the top-level post: read.
+  assert.equal(
+    countUnreadTopLevelObservedEvents(events, readAtFor(400, new Map())),
+    0,
+  );
+});
+
 test("latestObservedEvent_latestThreadReadDoesNotImplyChannelClear", () => {
   const events = new Map([
     ["older", observed("older", 400, "root-older")],
diff --git a/desktop/src/features/channels/unreadReadMarker.ts b/desktop/src/features/channels/unreadReadMarker.ts
new file mode 100644
index 0000000000..b6b6a62777
--- /dev/null
+++ b/desktop/src/features/channels/unreadReadMarker.ts
@@ -0,0 +1,57 @@
+import {
+  getThreadReference,
+  isBroadcastReply,
+} from "@/features/messages/lib/threading";
+import type { Channel } from "@/shared/api/types";
+import { CHANNEL_MESSAGE_EVENT_KINDS } from "@/shared/constants/kinds";
+import { DM_NOTIFIABLE_EVENT_KINDS } from "./isDmNotifiableKind";
+
+export function channelCatchUpEventKinds(
+  channelType: Channel["channelType"] | undefined,
+) {
+  return channelType === "dm"
+    ? DM_NOTIFIABLE_EVENT_KINDS
+    : CHANNEL_MESSAGE_EVENT_KINDS;
+}
+
+function parseTimestamp(value: string | null | undefined) {
+  if (!value) {
+    return null;
+  }
+
+  const timestamp = Date.parse(value);
+  return Number.isNaN(timestamp) ? null : timestamp;
+}
+
+function toUnixSeconds(isoOrMs: string | null | undefined): number | null {
+  const ms = parseTimestamp(isoOrMs);
+  return ms === null ? null : Math.floor(ms / 1_000);
+}
+
+// Resolve where the read marker should land when a channel is marked read.
+// Folds the caller's timeline position together with the newest event this
+// client has observed live (`observedLatest`), so an explicit "mark read" still
+// covers messages that arrived faster than channel metadata — this fold is
+// load-bearing for the Esc shortcut, sidebar mark-read, and empty-channel open,
+// all of which pass a null/stale caller value. `clearObserved` reports whether
+// the resulting marker covers the observed timestamp, signalling the caller to
+// drop its observed refs so the unread memo sees `latest === undefined` until a
+// genuinely newer event arrives.
+export function resolveChannelReadMarker(
+  callerReadAt: string | null | undefined,
+  observedLatest: number | undefined,
+): { markAt: number | null; clearObserved: boolean } {
+  const callerUnix = toUnixSeconds(callerReadAt);
+  const markAt = Math.max(callerUnix ?? 0, observedLatest ?? 0) || null;
+  return {
+    markAt,
+    clearObserved:
+      markAt !== null &&
+      observedLatest !== undefined &&
+      observedLatest <= markAt,
+  };
+}
+
+export function resolveObservedUnreadRootId(tags: string[][]): string | null {
+  return isBroadcastReply(tags) ? null : getThreadReference(tags).rootId;
+}
diff --git a/desktop/src/features/channels/useUnreadChannels.ts b/desktop/src/features/channels/useUnreadChannels.ts
index a2376f9b7b..e7f5e372b3 100644
--- a/desktop/src/features/channels/useUnreadChannels.ts
+++ b/desktop/src/features/channels/useUnreadChannels.ts
@@ -9,12 +9,18 @@ import {
   countUnreadBadgeObservedEvents,
   countUnreadHighPriorityObservedEvents,
   countUnreadObservedEvents,
+  countUnreadTopLevelObservedEvents,
   makeObservedUnreadEvent,
   mapsEqual,
   observedUnreadEventReadAt,
   recordObservedUnreadEvent,
   type ObservedUnreadEvent,
 } from "@/features/channels/unreadChannelCounts";
+import {
+  channelCatchUpEventKinds,
+  resolveChannelReadMarker,
+  resolveObservedUnreadRootId,
+} from "@/features/channels/unreadReadMarker";
 import { useReadState } from "@/features/channels/readState/useReadState";
 import { makeRootIdStore } from "@/features/channels/unreadRootIdStore";
 import {
@@ -32,9 +38,7 @@ import {
 } from "@/features/notifications/lib/shouldNotify";
 import type { RelayClient } from "@/shared/api/relayClientSession";
 import type { Channel, RelayEvent } from "@/shared/api/types";
-import { CHANNEL_MESSAGE_EVENT_KINDS } from "@/shared/constants/kinds";
 import { normalizeRelayUrl } from "@/features/profile/lib/selfProfileStorage";
-import { DM_NOTIFIABLE_EVENT_KINDS } from "./isDmNotifiableKind";
 import {
   activityScopeKey,
   addThreadActivityItems,
@@ -67,14 +71,6 @@ type UseUnreadChannelsOptions = UseLiveChannelUpdatesOptions & {
 // per-channel limit elsewhere in the app.
 const CATCH_UP_LIMIT = 1000;
 
-export function channelCatchUpEventKinds(
-  channelType: Channel["channelType"] | undefined,
-) {
-  return channelType === "dm"
-    ? DM_NOTIFIABLE_EVENT_KINDS
-    : CHANNEL_MESSAGE_EVENT_KINDS;
-}
-
 const participationStore = makeRootIdStore("buzz-thread-participation.v1");
 const authoredStore = makeRootIdStore("buzz-thread-authored.v1");
 // Thread roots where an external message @-mentioned the current user. The
@@ -83,48 +79,6 @@ const authoredStore = makeRootIdStore("buzz-thread-authored.v1");
 const mentionedStore = makeRootIdStore("buzz-thread-mentioned.v1");
 const mutedStore = makeRootIdStore("buzz-thread-muted.v1");
 
-function parseTimestamp(value: string | null | undefined) {
-  if (!value) {
-    return null;
-  }
-
-  const timestamp = Date.parse(value);
-  return Number.isNaN(timestamp) ? null : timestamp;
-}
-
-function toUnixSeconds(isoOrMs: string | null | undefined): number | null {
-  const ms = parseTimestamp(isoOrMs);
-  return ms === null ? null : Math.floor(ms / 1_000);
-}
-
-// Resolve where the read marker should land when a channel is marked read.
-// Folds the caller's timeline position together with the newest event this
-// client has observed live (`observedLatest`), so an explicit "mark read" still
-// covers messages that arrived faster than channel metadata — this fold is
-// load-bearing for the Esc shortcut, sidebar mark-read, and empty-channel open,
-// all of which pass a null/stale caller value. `clearObserved` reports whether
-// the resulting marker covers the observed timestamp, signalling the caller to
-// drop its observed refs so the unread memo sees `latest === undefined` until a
-// genuinely newer event arrives.
-export function resolveChannelReadMarker(
-  callerReadAt: string | null | undefined,
-  observedLatest: number | undefined,
-): { markAt: number | null; clearObserved: boolean } {
-  const callerUnix = toUnixSeconds(callerReadAt);
-  const markAt = Math.max(callerUnix ?? 0, observedLatest ?? 0) || null;
-  return {
-    markAt,
-    clearObserved:
-      markAt !== null &&
-      observedLatest !== undefined &&
-      observedLatest <= markAt,
-  };
-}
-
-export function resolveObservedUnreadRootId(tags: string[][]): string | null {
-  return isBroadcastReply(tags) ? null : getThreadReference(tags).rootId;
-}
-
 function setsEqual(a: ReadonlySet<string>, b: ReadonlySet<string>): boolean {
   if (a.size !== b.size) return false;
   for (const item of a) {
@@ -830,6 +784,7 @@ export function useUnreadChannels(
       if (!isReadStateReady) {
         return {
           unreadChannelIds: new Set<string>(),
+          topLevelUnreadChannelIds: new Set<string>(),
           highPriorityUnreadChannelIds: new Set<string>(),
           unreadChannelCounts: new Map<string, number>(),
           unreadChannelNotificationCount: 0,
@@ -837,6 +792,7 @@ export function useUnreadChannels(
       }
 
       const unread = new Set<string>();
+      const topLevelUnread = new Set<string>();
       const highPriority = new Set<string>();
       const counts = new Map<string, number>();
       let unreadChannelNotificationCount = 0;
@@ -847,6 +803,7 @@ export function useUnreadChannels(
         if (Object.hasOwn(forcedUnreadRef.current, channel.id)) {
           // Forced-unread is dot tier only — not high-priority.
           unread.add(channel.id);
+          topLevelUnread.add(channel.id);
           counts.set(channel.id, 1);
           unreadChannelNotificationCount += 1;
           continue;
@@ -873,6 +830,17 @@ export function useUnreadChannels(
         if (unreadCount === 0) continue;
 
         unread.add(channel.id);
+        // Channels whose unread includes a channel-level post — surfaces
+        // that clear by opening the channel (vs thread replies, which clear
+        // through thread read markers) distinguish the two via this set.
+        if (
+          countUnreadTopLevelObservedEvents(
+            observedEvents,
+            readAtForObservedEvent,
+          ) > 0
+        ) {
+          topLevelUnread.add(channel.id);
+        }
         const badgeCount = countUnreadBadgeObservedEvents(
           observedEvents,
           readAtForObservedEvent,
@@ -900,6 +868,7 @@ export function useUnreadChannels(
 
       return {
         unreadChannelIds: unread,
+        topLevelUnreadChannelIds: topLevelUnread,
         highPriorityUnreadChannelIds: highPriority,
         unreadChannelCounts: counts,
         unreadChannelNotificationCount,
@@ -917,6 +886,7 @@ export function useUnreadChannels(
   // Stabilize Set references: only replace when contents actually change,
   // so downstream memos don't re-run on every render when sets are equal.
   const prevUnreadRef = React.useRef<ReadonlySet<string>>(new Set());
+  const prevTopLevelUnreadRef = React.useRef<ReadonlySet<string>>(new Set());
   const prevHighPriorityRef = React.useRef<ReadonlySet<string>>(new Set());
   const prevUnreadCountsRef = React.useRef<ReadonlyMap<string, number>>(
     new Map(),
@@ -930,6 +900,14 @@ export function useUnreadChannels(
     : rawUnread.unreadChannelIds;
   prevUnreadRef.current = unreadChannelIds;
 
+  const topLevelUnreadChannelIds = setsEqual(
+    rawUnread.topLevelUnreadChannelIds,
+    prevTopLevelUnreadRef.current,
+  )
+    ? prevTopLevelUnreadRef.current
+    : rawUnread.topLevelUnreadChannelIds;
+  prevTopLevelUnreadRef.current = topLevelUnreadChannelIds;
+
   const highPriorityUnreadChannelIds = setsEqual(
     rawUnread.highPriorityUnreadChannelIds,
     prevHighPriorityRef.current,
@@ -992,6 +970,7 @@ export function useUnreadChannels(
 
   return {
     unreadChannelIds,
+    topLevelUnreadChannelIds,
     unreadChannelCounts,
     highPriorityUnreadChannelIds,
     unreadChannelNotificationCount,
diff --git a/desktop/src/features/dev-mode/lib/authorColors.ts b/desktop/src/features/dev-mode/lib/authorColors.ts
new file mode 100644
index 0000000000..36ff4056dc
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/authorColors.ts
@@ -0,0 +1,124 @@
+import * as React from "react";
+
+import { normalizePubkey } from "@/shared/lib/pubkey";
+
+/**
+ * Deterministic per-author name colors for developer mode, with optional
+ * per-pubkey hex overrides persisted in localStorage (set via the command
+ * palette). A synced profile color field would need schema/event changes, so
+ * overrides are device-local for now.
+ */
+
+/** Mid-lightness hues that stay readable on both dark and light themes. */
+export const AUTHOR_COLOR_PALETTE = [
+  "#e5484d", // red
+  "#f76b15", // orange
+  "#ffb224", // amber
+  "#46a758", // green
+  "#12a594", // teal
+  "#0091ff", // blue
+  "#3e63dd", // indigo
+  "#6e56cf", // violet
+  "#8e4ec6", // purple
+  "#e93d82", // pink
+  "#05a2c2", // cyan
+  "#978365", // bronze
+] as const;
+
+const STORAGE_KEY = "buzz.devMode.nameColors";
+const HEX_COLOR_RE = /^#[0-9a-f]{6}$/;
+
+const listeners = new Set<() => void>();
+
+let overrides = readStoredOverrides();
+
+function readStoredOverrides(): Record<string, string> {
+  try {
+    const raw = globalThis.localStorage?.getItem(STORAGE_KEY);
+    if (!raw) return {};
+    const parsed: unknown = JSON.parse(raw);
+    if (typeof parsed !== "object" || parsed === null) return {};
+    const valid: Record<string, string> = {};
+    for (const [pubkey, color] of Object.entries(parsed)) {
+      if (typeof color === "string" && HEX_COLOR_RE.test(color)) {
+        valid[pubkey] = color;
+      }
+    }
+    return valid;
+  } catch {
+    return {};
+  }
+}
+
+function subscribe(listener: () => void): () => void {
+  listeners.add(listener);
+  return () => {
+    listeners.delete(listener);
+  };
+}
+
+function getSnapshot(): Record<string, string> {
+  return overrides;
+}
+
+export function normalizeHexColor(value: string): string | null {
+  const trimmed = value.trim().toLowerCase();
+  const withHash = trimmed.startsWith("#") ? trimmed : `#${trimmed}`;
+  const expanded = /^#[0-9a-f]{3}$/.test(withHash)
+    ? `#${withHash[1]}${withHash[1]}${withHash[2]}${withHash[2]}${withHash[3]}${withHash[3]}`
+    : withHash;
+  return HEX_COLOR_RE.test(expanded) ? expanded : null;
+}
+
+export function setNameColorOverride(
+  pubkey: string,
+  color: string | null,
+): void {
+  const key = normalizePubkey(pubkey);
+  const next = { ...overrides };
+  if (color === null) {
+    delete next[key];
+  } else {
+    const normalized = normalizeHexColor(color);
+    if (!normalized) return;
+    next[key] = normalized;
+  }
+  overrides = next;
+  try {
+    globalThis.localStorage?.setItem(STORAGE_KEY, JSON.stringify(next));
+  } catch {
+    // Persistence is best-effort; the in-memory value still applies.
+  }
+  for (const listener of listeners) {
+    listener();
+  }
+}
+
+/** FNV-1a — stable across sessions, unlike per-run hashing. */
+function hashPubkey(pubkey: string): number {
+  let hash = 0x811c9dc5;
+  for (let index = 0; index < pubkey.length; index += 1) {
+    hash ^= pubkey.charCodeAt(index);
+    hash = Math.imul(hash, 0x01000193);
+  }
+  return hash >>> 0;
+}
+
+export function defaultAuthorColor(pubkey: string): string {
+  const key = normalizePubkey(pubkey);
+  return AUTHOR_COLOR_PALETTE[hashPubkey(key) % AUTHOR_COLOR_PALETTE.length];
+}
+
+export type AuthorColorResolver = (pubkey: string) => string;
+
+export function useAuthorColorResolver(): AuthorColorResolver {
+  const current = React.useSyncExternalStore(
+    subscribe,
+    getSnapshot,
+    getSnapshot,
+  );
+  return React.useCallback<AuthorColorResolver>(
+    (pubkey) => current[normalizePubkey(pubkey)] ?? defaultAuthorColor(pubkey),
+    [current],
+  );
+}
diff --git a/desktop/src/features/dev-mode/lib/channelNaming.ts b/desktop/src/features/dev-mode/lib/channelNaming.ts
new file mode 100644
index 0000000000..10dc5bf4a8
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/channelNaming.ts
@@ -0,0 +1,103 @@
+import { generateAgentCompletion } from "@/shared/api/agentCompletion";
+import { sanitizeChannelName } from "@/features/dev-mode/lib/sessionNaming";
+import { meshNodeStatus } from "@/shared/api/tauriMesh";
+
+/**
+ * Ask an LLM to title a session channel from its first prompt.
+ *
+ * Prefers a one-shot completion through a managed agent (the agent tagged in
+ * the composer, or any configured managed agent) via `buzz-acp complete` —
+ * a private subprocess exchange that never appears in a channel. Falls back
+ * to the mesh LLM node's OpenAI-compatible endpoint when one is running.
+ * Returns null (caller keeps its placeholder name) when neither produces a
+ * usable title — callers must not block channel creation on this.
+ */
+
+const TITLE_TIMEOUT_MS = 8_000;
+
+const TITLE_INSTRUCTION =
+  "Reply with only a 2-5 word kebab-case channel name summarizing the " +
+  "following chat prompt. No punctuation besides hyphens, no quotes, no " +
+  "explanation — just the name.";
+
+/** Reduce raw LLM output to a valid channel name, or null if unusable. */
+function toChannelName(raw: string): string | null {
+  // Keep only the last non-empty line — chatty agents sometimes preface the
+  // answer even when told not to.
+  const lastLine = raw
+    .split("\n")
+    .map((line) => line.trim())
+    .filter((line) => line.length > 0)
+    .at(-1);
+  if (!lastLine) return null;
+  const name = sanitizeChannelName(lastLine.replaceAll("-", " "));
+  return name.length >= 3 ? name : null;
+}
+
+async function agentTitle(
+  prompt: string,
+  agentPubkey: string,
+): Promise<string | null> {
+  try {
+    const text = await generateAgentCompletion({
+      pubkey: agentPubkey,
+      prompt: `${TITLE_INSTRUCTION}\n\nPrompt:\n${prompt.slice(0, 500)}`,
+      systemPrompt: TITLE_INSTRUCTION,
+    });
+    return toChannelName(text);
+  } catch {
+    return null;
+  }
+}
+
+async function meshTitle(prompt: string): Promise<string | null> {
+  let apiBaseUrl: string;
+  let modelId: string;
+  try {
+    const status = await meshNodeStatus();
+    if (status.state !== "running" || !status.apiBaseUrl || !status.modelId) {
+      return null;
+    }
+    apiBaseUrl = status.apiBaseUrl;
+    modelId = status.modelId;
+  } catch {
+    return null;
+  }
+
+  try {
+    const response = await fetch(`${apiBaseUrl}/chat/completions`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({
+        model: modelId,
+        messages: [
+          { role: "system", content: TITLE_INSTRUCTION },
+          { role: "user", content: prompt.slice(0, 500) },
+        ],
+        max_tokens: 24,
+        temperature: 0.2,
+      }),
+      signal: AbortSignal.timeout(TITLE_TIMEOUT_MS),
+    });
+    if (!response.ok) return null;
+    const payload: unknown = await response.json();
+    const content = (
+      payload as { choices?: { message?: { content?: unknown } }[] }
+    ).choices?.[0]?.message?.content;
+    if (typeof content !== "string") return null;
+    return toChannelName(content);
+  } catch {
+    return null;
+  }
+}
+
+export async function generateChannelTitle(
+  prompt: string,
+  agentPubkey?: string | null,
+): Promise<string | null> {
+  if (agentPubkey) {
+    const title = await agentTitle(prompt, agentPubkey);
+    if (title) return title;
+  }
+  return meshTitle(prompt);
+}
diff --git a/desktop/src/features/dev-mode/lib/channelRefs.tsx b/desktop/src/features/dev-mode/lib/channelRefs.tsx
new file mode 100644
index 0000000000..a770a53ef1
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/channelRefs.tsx
@@ -0,0 +1,41 @@
+import * as React from "react";
+
+/**
+ * Channel references for developer mode: `#channel-name` in message text is
+ * the wire format the standard UI and mobile already render as channel links,
+ * so dev mode reads and writes the same plain text. The shell provides the
+ * known channels and its open handler once; composers use them for `#`
+ * autocomplete and message rows use them to render clickable references.
+ */
+
+export type ChannelRef = { id: string; name: string };
+
+type ChannelRefsValue = {
+  channels: ChannelRef[];
+  openChannel: (channelId: string) => void;
+};
+
+const ChannelRefsContext = React.createContext<ChannelRefsValue>({
+  channels: [],
+  openChannel: () => {},
+});
+
+export function DevChannelRefsProvider({
+  channels,
+  openChannel,
+  children,
+}: ChannelRefsValue & { children: React.ReactNode }) {
+  const value = React.useMemo(
+    () => ({ channels, openChannel }),
+    [channels, openChannel],
+  );
+  return (
+    <ChannelRefsContext.Provider value={value}>
+      {children}
+    </ChannelRefsContext.Provider>
+  );
+}
+
+export function useChannelRefs(): ChannelRefsValue {
+  return React.useContext(ChannelRefsContext);
+}
diff --git a/desktop/src/features/dev-mode/lib/composerModePreference.ts b/desktop/src/features/dev-mode/lib/composerModePreference.ts
new file mode 100644
index 0000000000..20789dbf0f
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/composerModePreference.ts
@@ -0,0 +1,24 @@
+/**
+ * Remembers the composer's last-used target (an agent's pubkey, or "chat")
+ * across sessions, so the composer keeps pointing at the agent the user last
+ * talked to instead of resetting to the alphabetical default. Device-level
+ * preference, persisted in localStorage.
+ */
+
+const STORAGE_KEY = "buzz.devMode.lastComposerMode";
+
+export function loadLastComposerModeKey(): string | null {
+  try {
+    return globalThis.localStorage?.getItem(STORAGE_KEY) ?? null;
+  } catch {
+    return null;
+  }
+}
+
+export function storeLastComposerModeKey(key: string): void {
+  try {
+    globalThis.localStorage?.setItem(STORAGE_KEY, key);
+  } catch {
+    // Persistence is best-effort; the in-memory selection still applies.
+  }
+}
diff --git a/desktop/src/features/dev-mode/lib/copyLinkUrls.ts b/desktop/src/features/dev-mode/lib/copyLinkUrls.ts
new file mode 100644
index 0000000000..1f244eda93
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/copyLinkUrls.ts
@@ -0,0 +1,43 @@
+/**
+ * Transcript links render a fetched title ("joah in #general") instead of
+ * their URL, so a plain copy would lose the destination. This handler
+ * rewrites the plain-text clipboard so every DevLink serializes as its
+ * href, while text/html keeps the pretty labels for rich paste targets.
+ *
+ * Returns true when it handled the event (selection contained a DevLink).
+ */
+export function copySelectionWithLinkUrls(event: ClipboardEvent): boolean {
+  const selection = window.getSelection();
+  if (!selection || selection.isCollapsed || selection.rangeCount === 0) {
+    return false;
+  }
+
+  const container = document.createElement("div");
+  for (let i = 0; i < selection.rangeCount; i += 1) {
+    container.appendChild(selection.getRangeAt(i).cloneContents());
+  }
+  if (!container.querySelector("a[data-dev-link]")) {
+    return false;
+  }
+
+  const html = container.innerHTML;
+
+  for (const anchor of container.querySelectorAll("a[data-dev-link]")) {
+    const href = anchor.getAttribute("href");
+    if (href) anchor.replaceWith(document.createTextNode(href));
+  }
+
+  // innerText needs layout to turn block boundaries into newlines, so the
+  // clone briefly joins the document off-screen.
+  container.style.position = "fixed";
+  container.style.left = "-99999px";
+  container.style.top = "0";
+  document.body.appendChild(container);
+  const text = container.innerText;
+  container.remove();
+
+  event.clipboardData?.setData("text/plain", text);
+  event.clipboardData?.setData("text/html", html);
+  event.preventDefault();
+  return true;
+}
diff --git a/desktop/src/features/dev-mode/lib/devMarkdown.test.mjs b/desktop/src/features/dev-mode/lib/devMarkdown.test.mjs
new file mode 100644
index 0000000000..b7ecd36cfc
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/devMarkdown.test.mjs
@@ -0,0 +1,92 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { renderDevMarkdown } from "./devMarkdown.tsx";
+
+function elements(nodes, type) {
+  return nodes.filter(
+    (node) => typeof node === "object" && node !== null && node.type === type,
+  );
+}
+
+function textOf(node) {
+  if (node === null || node === undefined) return "";
+  if (typeof node === "string") return node;
+  if (Array.isArray(node)) return node.map(textOf).join("");
+  if (typeof node === "object") return textOf(node.props?.children);
+  return String(node);
+}
+
+test("plainText_staysOnePreWrapParagraph", () => {
+  const nodes = renderDevMarkdown("hello\nworld");
+  assert.equal(nodes.length, 1);
+  assert.equal(nodes[0].type, "p");
+  assert.equal(textOf(nodes[0]), "hello\nworld");
+});
+
+test("blankLine_splitsParagraphs", () => {
+  const nodes = renderDevMarkdown("one\n\ntwo");
+  assert.equal(elements(nodes, "p").length, 2);
+});
+
+test("fencedCode_rendersPreWithoutFenceLines", () => {
+  const nodes = renderDevMarkdown("before\n```ts\nconst a = 1;\n```\nafter");
+  const [pre] = elements(nodes, "pre");
+  assert.ok(pre);
+  assert.equal(textOf(pre), "const a = 1;");
+  assert.equal(elements(nodes, "p").length, 2);
+});
+
+test("unterminatedFence_capturesRestOfMessage", () => {
+  const nodes = renderDevMarkdown("```\nline1\nline2");
+  const [pre] = elements(nodes, "pre");
+  assert.equal(textOf(pre), "line1\nline2");
+});
+
+test("heading_rendersBoldWithoutHashes", () => {
+  const nodes = renderDevMarkdown("## Findings");
+  assert.equal(nodes.length, 1);
+  assert.equal(textOf(nodes[0]), "Findings");
+  assert.ok(nodes[0].props.className.includes("font-bold"));
+});
+
+test("bulletList_rendersMarkerAndInlineContent", () => {
+  const nodes = renderDevMarkdown("- **Saved rule state** — conforms");
+  assert.equal(nodes.length, 1);
+  const [marker, body] = nodes[0].props.children;
+  assert.equal(textOf(marker), "•");
+  assert.equal(textOf(body), "Saved rule state — conforms");
+});
+
+test("numberedList_keepsNumbers", () => {
+  const nodes = renderDevMarkdown("1. first\n2. second");
+  assert.equal(nodes.length, 2);
+  assert.equal(textOf(nodes[0].props.children[0]), "1.");
+  assert.equal(textOf(nodes[1].props.children[0]), "2.");
+});
+
+test("nestedListItem_indents", () => {
+  const nodes = renderDevMarkdown("- top\n  - nested");
+  assert.equal(nodes[1].props.style.paddingLeft, "2ch");
+});
+
+test("blockquote_groupsConsecutiveLines", () => {
+  const nodes = renderDevMarkdown("> one\n> two\nplain");
+  const [quote] = elements(nodes, "blockquote");
+  assert.equal(textOf(quote), "one\ntwo");
+  assert.equal(elements(nodes, "p").length, 1);
+});
+
+test("horizontalRule_rendersDivider", () => {
+  const nodes = renderDevMarkdown("above\n---\nbelow");
+  const divider = nodes.find(
+    (node) =>
+      typeof node === "object" && node.props?.className?.includes("border-t"),
+  );
+  assert.ok(divider);
+});
+
+test("hyphenListItem_isNotAHorizontalRule", () => {
+  const nodes = renderDevMarkdown("- item");
+  assert.equal(textOf(nodes[0].props.children[0]), "•");
+});
diff --git a/desktop/src/features/dev-mode/lib/devMarkdown.tsx b/desktop/src/features/dev-mode/lib/devMarkdown.tsx
new file mode 100644
index 0000000000..c45986c8a4
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/devMarkdown.tsx
@@ -0,0 +1,199 @@
+import type * as React from "react";
+
+import {
+  renderHighlightedContent,
+  type ChannelRefOptions,
+  type MentionStyle,
+} from "@/features/dev-mode/lib/highlightContent";
+import { cn } from "@/shared/lib/cn";
+import { Markdown } from "@/shared/ui/markdown";
+import type { ImetaLookup } from "@/shared/ui/markdown/types";
+
+/**
+ * Block-level markdown for developer-mode transcripts, layered over the
+ * span-based inline highlighter: fenced code blocks, headings, bullet and
+ * numbered lists, blockquotes, and horizontal rules. Everything renders as
+ * React nodes — never HTML — and keeps the terminal aesthetic (monospace,
+ * square corners). Anything unrecognized stays a pre-wrap paragraph, so
+ * plain human chat renders exactly as typed.
+ */
+
+const FENCE_RE = /^\s{0,3}```/;
+const HEADING_RE = /^(#{1,6})\s+(.+)$/;
+const LIST_ITEM_RE = /^(\s*)(?:([-*+])|(\d{1,3})[.)])\s+(.+)$/;
+const HR_RE = /^ {0,3}([-*_])\s*(?:\1\s*){2,}$/;
+const QUOTE_RE = /^ {0,3}>\s?(.*)$/;
+/** A standalone `![alt](url)` line — the shape `buildOutgoingMessage` emits
+ * for image/video attachments (URLs are paren- and space-free). */
+const MEDIA_LINE_RE = /^!\[([^\]]*)\]\((\S+)\)\s*$/;
+
+/**
+ * One attached image or video in a dev-mode transcript, rendered through the
+ * standard `Markdown` component so developer mode inherits the lightbox,
+ * context menus, video controls, and relay URL handling.
+ */
+function DevMediaBlock({
+  line,
+  imetaByUrl,
+}: {
+  line: string;
+  imetaByUrl: ImetaLookup | undefined;
+}) {
+  return (
+    <div className="my-1 min-w-0 max-w-md" data-block-media="">
+      <Markdown content={line} imetaByUrl={imetaByUrl} />
+    </div>
+  );
+}
+
+export function renderDevMarkdown(
+  content: string,
+  mentions: MentionStyle[] = [],
+  channelRefs?: ChannelRefOptions,
+  imetaByUrl?: ImetaLookup,
+): React.ReactNode[] {
+  const inline = (text: string) =>
+    renderHighlightedContent(text, mentions, channelRefs);
+
+  const lines = content.split("\n");
+  const nodes: React.ReactNode[] = [];
+  let paragraph: string[] = [];
+  let quote: string[] = [];
+
+  const flushParagraph = () => {
+    if (paragraph.length === 0) return;
+    nodes.push(
+      <p key={`p${nodes.length}`} className="whitespace-pre-wrap">
+        {inline(paragraph.join("\n"))}
+      </p>,
+    );
+    paragraph = [];
+  };
+
+  const flushQuote = () => {
+    if (quote.length === 0) return;
+    nodes.push(
+      <blockquote
+        key={`q${nodes.length}`}
+        className="whitespace-pre-wrap border-l-2 border-border pl-2 text-muted-foreground"
+      >
+        {inline(quote.join("\n"))}
+      </blockquote>,
+    );
+    quote = [];
+  };
+
+  let i = 0;
+  while (i < lines.length) {
+    const line = lines[i];
+
+    if (FENCE_RE.test(line)) {
+      flushParagraph();
+      flushQuote();
+      const code: string[] = [];
+      i += 1;
+      while (i < lines.length && !FENCE_RE.test(lines[i])) {
+        code.push(lines[i]);
+        i += 1;
+      }
+      i += 1; // Closing fence (or end of message on an unterminated fence).
+      nodes.push(
+        <pre
+          key={`c${nodes.length}`}
+          className="my-1 overflow-x-auto rounded-none border border-border/50 bg-muted/40 px-2 py-1"
+        >
+          {code.join("\n")}
+        </pre>,
+      );
+      continue;
+    }
+
+    const quoted = QUOTE_RE.exec(line);
+    if (quoted) {
+      flushParagraph();
+      quote.push(quoted[1]);
+      i += 1;
+      continue;
+    }
+    flushQuote();
+
+    if (line.trim() === "") {
+      flushParagraph();
+      i += 1;
+      continue;
+    }
+
+    if (HR_RE.test(line)) {
+      flushParagraph();
+      nodes.push(
+        <div
+          key={`hr${nodes.length}`}
+          className="my-1 border-t border-border/40"
+        />,
+      );
+      i += 1;
+      continue;
+    }
+
+    const heading = HEADING_RE.exec(line);
+    if (heading) {
+      flushParagraph();
+      const level = heading[1].length;
+      nodes.push(
+        <div
+          key={`h${nodes.length}`}
+          className={cn(
+            level <= 2 ? "font-bold" : "font-semibold",
+            level === 1 && "text-base",
+          )}
+        >
+          {inline(heading[2])}
+        </div>,
+      );
+      i += 1;
+      continue;
+    }
+
+    const media = MEDIA_LINE_RE.exec(line.trim());
+    if (media) {
+      flushParagraph();
+      nodes.push(
+        <DevMediaBlock
+          key={`m${nodes.length}`}
+          imetaByUrl={imetaByUrl}
+          line={line.trim()}
+        />,
+      );
+      i += 1;
+      continue;
+    }
+
+    const item = LIST_ITEM_RE.exec(line);
+    if (item) {
+      flushParagraph();
+      const [, indent, bullet, number, rest] = item;
+      nodes.push(
+        <div
+          key={`li${nodes.length}`}
+          className="flex"
+          style={indent ? { paddingLeft: `${indent.length}ch` } : undefined}
+        >
+          <span className="shrink-0 select-none pr-2 text-muted-foreground">
+            {bullet ? "•" : `${number}.`}
+          </span>
+          <span className="min-w-0 flex-1 whitespace-pre-wrap">
+            {inline(rest)}
+          </span>
+        </div>,
+      );
+      i += 1;
+      continue;
+    }
+
+    paragraph.push(line);
+    i += 1;
+  }
+  flushParagraph();
+  flushQuote();
+  return nodes;
+}
diff --git a/desktop/src/features/dev-mode/lib/displayStylePreference.ts b/desktop/src/features/dev-mode/lib/displayStylePreference.ts
new file mode 100644
index 0000000000..23bf303d84
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/displayStylePreference.ts
@@ -0,0 +1,78 @@
+import * as React from "react";
+
+/**
+ * App-wide display style.
+ *
+ * - `standard` — the default sidebar + channel pane layout.
+ * - `developer` — a prompt-first, terminal-style surface: one composer that
+ *   spawns a channel per prompt with an agent tagged (Tab cycles the target
+ *   agent), plus keyboard-driven session navigation.
+ *
+ * Persisted in localStorage. Device-level UI preference, not community-scoped.
+ */
+export type DisplayStyle = "standard" | "developer";
+
+const STORAGE_KEY = "buzz.displayStyle";
+
+const DEFAULT_DISPLAY_STYLE: DisplayStyle = "standard";
+
+const listeners = new Set<() => void>();
+
+let displayStyle = readStoredDisplayStyle();
+
+function parseDisplayStyle(value: string | null | undefined): DisplayStyle {
+  return value === "standard" || value === "developer"
+    ? value
+    : DEFAULT_DISPLAY_STYLE;
+}
+
+function readStoredDisplayStyle(): DisplayStyle {
+  try {
+    return parseDisplayStyle(globalThis.localStorage?.getItem(STORAGE_KEY));
+  } catch {
+    return DEFAULT_DISPLAY_STYLE;
+  }
+}
+
+function subscribe(listener: () => void): () => void {
+  listeners.add(listener);
+  return () => {
+    listeners.delete(listener);
+  };
+}
+
+function getSnapshot(): DisplayStyle {
+  return displayStyle;
+}
+
+function getServerSnapshot(): DisplayStyle {
+  return DEFAULT_DISPLAY_STYLE;
+}
+
+/** Read the persisted display style outside of React. */
+export function getDisplayStyle(): DisplayStyle {
+  return displayStyle;
+}
+
+/** Update the display style and notify all subscribed components. */
+export function setDisplayStyle(style: DisplayStyle): void {
+  displayStyle = style;
+
+  try {
+    globalThis.localStorage?.setItem(STORAGE_KEY, style);
+  } catch {
+    // Persistence is best-effort; the in-memory value still applies.
+  }
+
+  for (const listener of listeners) {
+    listener();
+  }
+}
+
+export function toggleDisplayStyle(): void {
+  setDisplayStyle(displayStyle === "developer" ? "standard" : "developer");
+}
+
+export function useDisplayStyle(): DisplayStyle {
+  return React.useSyncExternalStore(subscribe, getSnapshot, getServerSnapshot);
+}
diff --git a/desktop/src/features/dev-mode/lib/highlightContent.test.mjs b/desktop/src/features/dev-mode/lib/highlightContent.test.mjs
new file mode 100644
index 0000000000..6460cf88a7
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/highlightContent.test.mjs
@@ -0,0 +1,180 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  matchLeadingMention,
+  renderHighlightedContent,
+} from "./highlightContent.tsx";
+
+const channels = [
+  { id: "c1", name: "fix login bug" },
+  { id: "c2", name: "fix login bug in prod" },
+  { id: "c3", name: "deploys" },
+];
+
+function channelRefOpts(onOpen = () => {}) {
+  return { channels, onOpen };
+}
+
+function buttons(nodes) {
+  return nodes.filter(
+    (node) =>
+      typeof node === "object" && node !== null && node.type === "button",
+  );
+}
+
+test("knownChannelRef_rendersClickableButton", () => {
+  let opened = null;
+  const nodes = renderHighlightedContent(
+    "see #deploys for status",
+    [],
+    channelRefOpts((id) => {
+      opened = id;
+    }),
+  );
+  const [button] = buttons(nodes);
+  assert.ok(button, "expected a button node for the channel ref");
+  assert.equal(button.props.children, "#deploys");
+  button.props.onClick();
+  assert.equal(opened, "c3");
+});
+
+test("unknownChannelRef_staysPlainText", () => {
+  const nodes = renderHighlightedContent(
+    "priority #1 for today",
+    [],
+    channelRefOpts(),
+  );
+  assert.equal(buttons(nodes).length, 0);
+  assert.ok(nodes.join("").includes("#1"));
+});
+
+test("channelRef_withoutOptions_staysPlainText", () => {
+  const nodes = renderHighlightedContent("see #deploys");
+  assert.equal(buttons(nodes).length, 0);
+});
+
+test("channelRef_matchesLongestNameWithSpaces", () => {
+  const nodes = renderHighlightedContent(
+    "tracking #fix login bug in prod now",
+    [],
+    channelRefOpts(),
+  );
+  const [button] = buttons(nodes);
+  assert.ok(button);
+  assert.equal(button.props.children, "#fix login bug in prod");
+  // Remaining prose after the ref is preserved.
+  const tail = nodes[nodes.indexOf(button) + 1];
+  assert.equal(tail, " now");
+});
+
+test("channelRef_matchIsCaseInsensitive", () => {
+  const nodes = renderHighlightedContent("see #Deploys", [], channelRefOpts());
+  const [button] = buttons(nodes);
+  assert.ok(button);
+  assert.equal(button.props.children, "#Deploys");
+});
+
+test("channelRef_requiresBoundaryAfterName", () => {
+  // "#deploysX" is not the known channel "deploys".
+  const nodes = renderHighlightedContent("see #deploysX", [], channelRefOpts());
+  assert.equal(buttons(nodes).length, 0);
+});
+
+function findByType(nodes, type) {
+  return nodes.find(
+    (node) => typeof node === "object" && node !== null && node.type === type,
+  );
+}
+
+test("boldMarkdown_rendersStrongWithoutMarkers", () => {
+  const nodes = renderHighlightedContent("**Verified (independently)** — ok");
+  const strong = findByType(nodes, "strong");
+  assert.ok(strong);
+  assert.deepEqual(strong.props.children, ["Verified (independently)"]);
+  assert.ok(nodes.includes(" — ok"));
+});
+
+test("italicMarkdown_rendersEm", () => {
+  const star = findByType(
+    renderHighlightedContent("really *important* here"),
+    "em",
+  );
+  assert.deepEqual(star.props.children, ["important"]);
+  const underscore = findByType(
+    renderHighlightedContent("really _important_ here"),
+    "em",
+  );
+  assert.deepEqual(underscore.props.children, ["important"]);
+});
+
+test("strikeMarkdown_rendersDel", () => {
+  const del = findByType(
+    renderHighlightedContent("~~old plan~~ new plan"),
+    "del",
+  );
+  assert.deepEqual(del.props.children, ["old plan"]);
+});
+
+test("boldContainingInlineCode_nestsHighlighting", () => {
+  const strong = findByType(
+    renderHighlightedContent("**uses `flag`**"),
+    "strong",
+  );
+  assert.ok(strong);
+  const [prefix, code] = strong.props.children;
+  assert.equal(prefix, "uses ");
+  assert.equal(code.props.children, "flag");
+});
+
+test("snakeCaseAndArithmetic_stayPlainProse", () => {
+  for (const text of ["field_for_json stays", "2*3*4 = 24", "a ** b"]) {
+    const nodes = renderHighlightedContent(text);
+    assert.equal(findByType(nodes, "em"), undefined, text);
+    assert.equal(findByType(nodes, "strong"), undefined, text);
+  }
+});
+
+test("markdownLink_rendersDevLinkWithLabel", () => {
+  const nodes = renderHighlightedContent(
+    "see [the PR](https://github.com/x/y/pull/1).",
+  );
+  const link = nodes.find(
+    (node) => typeof node === "object" && node !== null && node.props?.href,
+  );
+  assert.ok(link);
+  assert.equal(link.props.href, "https://github.com/x/y/pull/1");
+  assert.equal(link.props.label, "the PR");
+  assert.equal(nodes.at(-1), ".");
+});
+
+const ampMention = { name: "amp (local)", color: "#00bcd4" };
+
+test("leadingMention_knownName_matchesPastTrailingSpace", () => {
+  const directed = matchLeadingMention("@amp (local) open a PR", [ampMention]);
+  assert.ok(directed);
+  assert.equal(directed.mention.name, "amp (local)");
+  assert.equal("@amp (local) open a PR".slice(directed.end), "open a PR");
+});
+
+test("leadingMention_matchesEntireMessage", () => {
+  const directed = matchLeadingMention("@amp (local)", [ampMention]);
+  assert.ok(directed);
+  assert.equal("@amp (local)".slice(directed.end), "");
+});
+
+test("leadingMention_midMessageMention_doesNotMatch", () => {
+  assert.equal(
+    matchLeadingMention("ask @amp (local) later", [ampMention]),
+    null,
+  );
+});
+
+test("leadingMention_unknownName_doesNotMatch", () => {
+  assert.equal(matchLeadingMention("@stranger hello", [ampMention]), null);
+});
+
+test("leadingMention_requiresBoundaryAfterName", () => {
+  // "@amp (local)x" is not the known mention "amp (local)".
+  assert.equal(matchLeadingMention("@amp (local)x hi", [ampMention]), null);
+});
diff --git a/desktop/src/features/dev-mode/lib/highlightContent.tsx b/desktop/src/features/dev-mode/lib/highlightContent.tsx
new file mode 100644
index 0000000000..33f16a89b9
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/highlightContent.tsx
@@ -0,0 +1,220 @@
+import type * as React from "react";
+
+import type { ChannelRef } from "@/features/dev-mode/lib/channelRefs";
+import { DevLink } from "@/features/dev-mode/ui/DevLink";
+
+/**
+ * Conservative keyword highlighting for developer-mode transcripts. Message
+ * text is tokenized into React spans — never HTML — so arbitrary content
+ * stays inert. Highlighted tokens: `inline code`, markdown emphasis
+ * (**bold**, *italic*, _italic_, ~~strike~~), [label](url) links, bare URLs,
+ * @mentions, and #channel references to known channels.
+ *
+ * Emphasis delimiters are deliberately strict — no space just inside the
+ * markers, and `*`/`_`/`~` openers can't start mid-word — so snake_case and
+ * arithmetic like `2*3*4` stay plain prose.
+ */
+
+const TOKEN_RE =
+  /(`[^`\n]+`|\[[^\]\n]+\]\(https?:\/\/[^\s)]+\)|\*\*(?!\s)[^\n]+?(?<=\S)\*\*|(?<![\w*])\*(?![\s*])[^*\n]+?(?<=\S)\*|(?<![\w~])~~(?!\s)[^\n]+?(?<=\S)~~|(?<![\w_])_(?![\s_])[^_\n]+?(?<=\S)_|https?:\/\/[^\s<>"')\]]+|@[\w./-]+|#[\w./-]+)/g;
+
+const MD_LINK_RE = /^\[([^\]\n]+)\]\((https?:\/\/[^\s)]+)\)$/;
+
+/** Same boundary the composer's mention-prefix check uses. */
+const MENTION_BOUNDARY_RE = /[\s,.;:!?)\]]/;
+
+/** A name the message explicitly mentions (from its p tags) and its chat color. */
+export type MentionStyle = { name: string; color: string };
+
+/** Click handling for `#channel-name` references to known channels. */
+export type ChannelRefOptions = {
+  channels: ChannelRef[];
+  onOpen: (channelId: string) => void;
+};
+
+/**
+ * Longest known channel name (case-insensitive) starting right after the `#`
+ * at `hashIndex`, with the same word-boundary rule mentions use.
+ */
+function matchKnownChannel(
+  content: string,
+  hashIndex: number,
+  channels: ChannelRef[],
+): ChannelRef | null {
+  let best: ChannelRef | null = null;
+  for (const channel of channels) {
+    if (best && channel.name.length <= best.name.length) continue;
+    const end = hashIndex + 1 + channel.name.length;
+    const candidate = content.slice(hashIndex + 1, end);
+    if (candidate.toLowerCase() !== channel.name.toLowerCase()) continue;
+    const after = content[end];
+    if (after !== undefined && !MENTION_BOUNDARY_RE.test(after)) continue;
+    best = channel;
+  }
+  return best;
+}
+
+/**
+ * Longest known name (case-insensitive) starting right after the `@` at
+ * `atIndex`. Names may contain spaces/parens — e.g. "amp (local)" — which the
+ * generic token regex cannot capture.
+ */
+function matchKnownMention(
+  content: string,
+  atIndex: number,
+  mentions: MentionStyle[],
+): MentionStyle | null {
+  let best: MentionStyle | null = null;
+  for (const mention of mentions) {
+    if (best && mention.name.length <= best.name.length) continue;
+    const end = atIndex + 1 + mention.name.length;
+    const candidate = content.slice(atIndex + 1, end);
+    if (candidate.toLowerCase() !== mention.name.toLowerCase()) continue;
+    const after = content[end];
+    if (after !== undefined && !MENTION_BOUNDARY_RE.test(after)) continue;
+    best = mention;
+  }
+  return best;
+}
+
+/**
+ * A known mention the message text opens with (`@Name …`). Dev mode lifts it
+ * out of the body and renders it as a "to Name" line under the author name;
+ * `end` is the content offset just past the mention and its trailing space.
+ */
+export function matchLeadingMention(
+  content: string,
+  mentions: MentionStyle[],
+): { mention: MentionStyle; end: number } | null {
+  if (!content.startsWith("@")) return null;
+  const known = matchKnownMention(content, 0, mentions);
+  if (!known) return null;
+  let end = 1 + known.name.length;
+  while (end < content.length && /\s/.test(content[end])) end += 1;
+  return { mention: known, end };
+}
+
+export function renderHighlightedContent(
+  content: string,
+  mentions: MentionStyle[] = [],
+  channelRefs?: ChannelRefOptions,
+): React.ReactNode[] {
+  const nodes: React.ReactNode[] = [];
+  const re = new RegExp(TOKEN_RE.source, "g");
+  let lastIndex = 0;
+  let match = re.exec(content);
+  while (match !== null) {
+    const index = match.index;
+    if (index > lastIndex) {
+      nodes.push(content.slice(lastIndex, index));
+    }
+    const token = match[0];
+    if (token.startsWith("`")) {
+      nodes.push(
+        <span
+          key={`${index}-code`}
+          className="rounded-none bg-muted/60 px-0.5 text-amber-500 dark:text-amber-300"
+        >
+          {token.slice(1, -1)}
+        </span>,
+      );
+      lastIndex = index + token.length;
+    } else if (token.startsWith("[")) {
+      const link = MD_LINK_RE.exec(token);
+      if (link) {
+        nodes.push(
+          <DevLink href={link[2]} key={`${index}-mdlink`} label={link[1]} />,
+        );
+      } else {
+        nodes.push(token);
+      }
+      lastIndex = index + token.length;
+    } else if (token.startsWith("**")) {
+      nodes.push(
+        <strong className="font-semibold" key={`${index}-bold`}>
+          {renderHighlightedContent(token.slice(2, -2), mentions, channelRefs)}
+        </strong>,
+      );
+      lastIndex = index + token.length;
+    } else if (token.startsWith("~~")) {
+      nodes.push(
+        <del className="line-through" key={`${index}-strike`}>
+          {renderHighlightedContent(token.slice(2, -2), mentions, channelRefs)}
+        </del>,
+      );
+      lastIndex = index + token.length;
+    } else if (token.startsWith("*") || token.startsWith("_")) {
+      nodes.push(
+        <em className="italic" key={`${index}-em`}>
+          {renderHighlightedContent(token.slice(1, -1), mentions, channelRefs)}
+        </em>,
+      );
+      lastIndex = index + token.length;
+    } else if (token.startsWith("@")) {
+      const known = matchKnownMention(content, index, mentions);
+      if (known) {
+        const end = index + 1 + known.name.length;
+        // Colored text only — the composer's mode pill is the one boxed
+        // mention; in-message mentions render unboxed.
+        nodes.push(
+          <span
+            key={`${index}-mention`}
+            className="font-medium"
+            style={{ color: known.color }}
+          >
+            {content.slice(index, end)}
+          </span>,
+        );
+        lastIndex = end;
+        re.lastIndex = end;
+      } else {
+        nodes.push(
+          <span key={`${index}-mention`} className="font-medium text-sky-500">
+            {token}
+          </span>,
+        );
+        lastIndex = index + token.length;
+      }
+    } else if (token.startsWith("#")) {
+      const known = channelRefs
+        ? matchKnownChannel(content, index, channelRefs.channels)
+        : null;
+      if (known && channelRefs) {
+        const end = index + 1 + known.name.length;
+        const onOpen = channelRefs.onOpen;
+        // mousedown is prevented so a click never pulls focus off the
+        // composer — the same rule message clicks follow.
+        nodes.push(
+          <button
+            key={`${index}-channel`}
+            className="cursor-pointer font-medium text-sky-500 hover:underline"
+            onClick={() => onOpen(known.id)}
+            onMouseDown={(event) => event.preventDefault()}
+            type="button"
+          >
+            {content.slice(index, end)}
+          </button>,
+        );
+        lastIndex = end;
+        re.lastIndex = end;
+      } else {
+        // `#word` that is not a known channel is ordinary prose.
+        nodes.push(token);
+        lastIndex = index + token.length;
+      }
+    } else {
+      // Sentence punctuation after a URL belongs to the prose, not the href.
+      const href = token.replace(/[.,;:!?]+$/, "");
+      nodes.push(<DevLink href={href} key={`${index}-url`} />);
+      if (href.length < token.length) {
+        nodes.push(token.slice(href.length));
+      }
+      lastIndex = index + token.length;
+    }
+    match = re.exec(content);
+  }
+  if (lastIndex < content.length) {
+    nodes.push(content.slice(lastIndex));
+  }
+  return nodes;
+}
diff --git a/desktop/src/features/dev-mode/lib/linkDisplay.test.mjs b/desktop/src/features/dev-mode/lib/linkDisplay.test.mjs
new file mode 100644
index 0000000000..6fb051da1d
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/linkDisplay.test.mjs
@@ -0,0 +1,23 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { linkDisplayText } from "./linkDisplay.ts";
+
+test("linkDisplayText_stripsSchemeAndTrailingSlash", () => {
+  assert.equal(linkDisplayText("https://example.com/"), "example.com");
+  assert.equal(linkDisplayText("http://example.com/docs"), "example.com/docs");
+});
+
+test("linkDisplayText_keepsPathQueryAndFragment", () => {
+  assert.equal(
+    linkDisplayText("https://mail.google.com/mail/u/0/#drafts?compose=abc"),
+    "mail.google.com/mail/u/0/#drafts?compose=abc",
+  );
+});
+
+test("linkDisplayText_truncatesLongUrlsWithEllipsis", () => {
+  const display = linkDisplayText(`https://example.com/${"a".repeat(100)}`);
+  assert.equal(display.length, 64);
+  assert.ok(display.endsWith("…"));
+  assert.ok(display.startsWith("example.com/"));
+});
diff --git a/desktop/src/features/dev-mode/lib/linkDisplay.ts b/desktop/src/features/dev-mode/lib/linkDisplay.ts
new file mode 100644
index 0000000000..56aade8753
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/linkDisplay.ts
@@ -0,0 +1,9 @@
+const MAX_DISPLAY_CHARS = 64;
+
+/** Slack-style link text: no scheme, no trailing slash, tail-truncated. */
+export function linkDisplayText(href: string): string {
+  const stripped = href.replace(/^https?:\/\//, "").replace(/\/$/, "");
+  return stripped.length > MAX_DISPLAY_CHARS
+    ? `${stripped.slice(0, MAX_DISPLAY_CHARS - 1)}…`
+    : stripped;
+}
diff --git a/desktop/src/features/dev-mode/lib/membershipEvents.test.mjs b/desktop/src/features/dev-mode/lib/membershipEvents.test.mjs
new file mode 100644
index 0000000000..5aa60359a2
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/membershipEvents.test.mjs
@@ -0,0 +1,113 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  parseMembershipEvent,
+  selectMembershipEvents,
+} from "./membershipEvents.ts";
+
+const KIND_SYSTEM_MESSAGE = 40099;
+const ALICE = "a".repeat(64);
+const BOB = "b".repeat(64);
+
+let nextId = 0;
+function systemEvent(payload, createdAt = 1_000) {
+  nextId += 1;
+  return {
+    id: `sys-${nextId}`,
+    kind: KIND_SYSTEM_MESSAGE,
+    pubkey: "relay",
+    created_at: createdAt,
+    content: JSON.stringify(payload),
+    tags: [],
+  };
+}
+
+test("self-join parses as joined", () => {
+  const change = parseMembershipEvent(
+    systemEvent({ type: "member_joined", actor: ALICE, target: ALICE }),
+  );
+  assert.equal(change.change, "joined");
+  assert.equal(change.member, ALICE);
+  assert.equal(change.actor, null);
+});
+
+test("join by another member parses as added with actor", () => {
+  const change = parseMembershipEvent(
+    systemEvent({ type: "member_joined", actor: ALICE, target: BOB }),
+  );
+  assert.equal(change.change, "added");
+  assert.equal(change.member, BOB);
+  assert.equal(change.actor, ALICE);
+});
+
+test("member_left names the actor as the departing member", () => {
+  const change = parseMembershipEvent(
+    systemEvent({ type: "member_left", actor: BOB }),
+  );
+  assert.equal(change.change, "left");
+  assert.equal(change.member, BOB);
+  assert.equal(change.actor, null);
+});
+
+test("member_removed carries the removing actor", () => {
+  const change = parseMembershipEvent(
+    systemEvent({ type: "member_removed", actor: ALICE, target: BOB }),
+  );
+  assert.equal(change.change, "removed");
+  assert.equal(change.member, BOB);
+  assert.equal(change.actor, ALICE);
+});
+
+test("non-membership system messages and other kinds are ignored", () => {
+  assert.equal(
+    parseMembershipEvent(
+      systemEvent({ type: "topic_changed", actor: ALICE, topic: "x" }),
+    ),
+    null,
+  );
+  assert.equal(
+    parseMembershipEvent({
+      id: "m1",
+      kind: 40002,
+      pubkey: ALICE,
+      created_at: 1,
+      content: "hello",
+      tags: [],
+    }),
+    null,
+  );
+  assert.equal(
+    parseMembershipEvent({
+      id: "bad",
+      kind: KIND_SYSTEM_MESSAGE,
+      pubkey: "relay",
+      created_at: 1,
+      content: "not json",
+      tags: [],
+    }),
+    null,
+  );
+});
+
+test("selectMembershipEvents filters and sorts oldest first", () => {
+  const events = [
+    systemEvent({ type: "member_left", actor: BOB }, 300),
+    {
+      id: "m1",
+      kind: 40002,
+      pubkey: ALICE,
+      created_at: 150,
+      content: "hi",
+      tags: [],
+    },
+    systemEvent({ type: "member_joined", actor: BOB, target: BOB }, 100),
+    systemEvent({ type: "channel_created", actor: ALICE }, 200),
+  ];
+  const changes = selectMembershipEvents(events);
+  assert.deepEqual(
+    changes.map((change) => change.change),
+    ["joined", "left"],
+  );
+  assert.ok(changes[0].event.created_at < changes[1].event.created_at);
+});
diff --git a/desktop/src/features/dev-mode/lib/membershipEvents.ts b/desktop/src/features/dev-mode/lib/membershipEvents.ts
new file mode 100644
index 0000000000..8605d3c889
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/membershipEvents.ts
@@ -0,0 +1,70 @@
+import { byCreatedAscending } from "@/features/dev-mode/lib/transcriptRoots";
+import type { RelayEvent } from "@/shared/api/types";
+import { KIND_SYSTEM_MESSAGE } from "@/shared/constants/kinds";
+import { normalizePubkey } from "@/shared/lib/pubkey";
+
+/**
+ * A member entering or leaving the channel, parsed from a relay-signed
+ * kind:40099 system message. Other system message types (topic changes,
+ * channel_created, …) are ignored — dev mode's transcript only narrates
+ * membership.
+ */
+export type MembershipChange = {
+  event: RelayEvent;
+  change: "joined" | "added" | "left" | "removed";
+  /** The member who entered or left. */
+  member: string;
+  /** Who added/removed them — present only when different from `member`. */
+  actor: string | null;
+};
+
+export function parseMembershipEvent(
+  event: RelayEvent,
+): MembershipChange | null {
+  if (event.kind !== KIND_SYSTEM_MESSAGE) return null;
+
+  let payload: { type?: string; actor?: string; target?: string };
+  try {
+    payload = JSON.parse(event.content) as typeof payload;
+  } catch {
+    return null;
+  }
+
+  const actor = payload.actor ? normalizePubkey(payload.actor) : null;
+  const target = payload.target ? normalizePubkey(payload.target) : null;
+
+  switch (payload.type) {
+    case "member_joined": {
+      if (!target) return null;
+      if (actor && actor !== target) {
+        return { event, change: "added", member: target, actor };
+      }
+      return { event, change: "joined", member: target, actor: null };
+    }
+    case "member_left": {
+      if (!actor) return null;
+      return { event, change: "left", member: actor, actor: null };
+    }
+    case "member_removed": {
+      if (!target) return null;
+      return {
+        event,
+        change: "removed",
+        member: target,
+        actor: actor && actor !== target ? actor : null,
+      };
+    }
+    default:
+      return null;
+  }
+}
+
+/** Membership changes in a channel timeline, oldest first. */
+export function selectMembershipEvents(
+  events: RelayEvent[] | undefined,
+): MembershipChange[] {
+  return (events ?? [])
+    .map(parseMembershipEvent)
+    .filter((change): change is MembershipChange => change !== null)
+    .sort((left, right) => byCreatedAscending(left.event, right.event));
+}
diff --git a/desktop/src/features/dev-mode/lib/mentionRecords.test.mjs b/desktop/src/features/dev-mode/lib/mentionRecords.test.mjs
new file mode 100644
index 0000000000..b735241b32
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/mentionRecords.test.mjs
@@ -0,0 +1,79 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { extractMentions } from "./mentionRecords.ts";
+
+const joah = { name: "Joah", pubkey: "AA11", isAgent: false };
+const amp = { name: "amp", pubkey: "bb22", isAgent: true };
+const ampLocal = { name: "amp (local)", pubkey: "cc33", isAgent: true };
+
+test("finds a mention at the start of the text", () => {
+  const found = extractMentions("@Joah take a look", [joah]);
+  assert.deepEqual(
+    found.map((record) => record.pubkey),
+    ["AA11"],
+  );
+});
+
+test("finds a mid-sentence mention after whitespace", () => {
+  const found = extractMentions("ping @Joah about this", [joah]);
+  assert.equal(found.length, 1);
+});
+
+test("matching is case-insensitive", () => {
+  const found = extractMentions("@joah hello", [joah]);
+  assert.equal(found.length, 1);
+});
+
+test("trailing punctuation does not break the match", () => {
+  const found = extractMentions("@Joah, thoughts?", [joah]);
+  assert.equal(found.length, 1);
+});
+
+test("an email address is not a mention", () => {
+  const found = extractMentions("mail joah@example.com please", [
+    joah,
+    { name: "example.com", pubkey: "dd44", isAgent: false },
+  ]);
+  assert.equal(found.length, 0);
+});
+
+test("a record whose name is absent from the text is not extracted", () => {
+  const found = extractMentions("no mentions here", [joah, amp]);
+  assert.equal(found.length, 0);
+});
+
+test("longest name wins: @amp (local) never counts as @amp", () => {
+  const found = extractMentions("@amp (local) run the tests", [amp, ampLocal]);
+  assert.deepEqual(
+    found.map((record) => record.pubkey),
+    ["cc33"],
+  );
+});
+
+test("both names extract when both are genuinely mentioned", () => {
+  const found = extractMentions("@amp (local) and @amp should sync", [
+    amp,
+    ampLocal,
+  ]);
+  assert.deepEqual(found.map((record) => record.pubkey).sort(), [
+    "bb22",
+    "cc33",
+  ]);
+});
+
+test("duplicate pubkeys collapse to one record", () => {
+  const alias = { name: "Joah G", pubkey: "aa11", isAgent: false };
+  const found = extractMentions("@Joah and @Joah G", [joah, alias]);
+  assert.equal(found.length, 1);
+});
+
+test("a mention inside a word does not match", () => {
+  const found = extractMentions("email@Joah is not a mention", [joah]);
+  assert.equal(found.length, 0);
+});
+
+test("bracketed mentions match", () => {
+  const found = extractMentions("(@Joah) and [@amp]", [joah, amp]);
+  assert.equal(found.length, 2);
+});
diff --git a/desktop/src/features/dev-mode/lib/mentionRecords.ts b/desktop/src/features/dev-mode/lib/mentionRecords.ts
new file mode 100644
index 0000000000..39ff2b75f4
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/mentionRecords.ts
@@ -0,0 +1,42 @@
+/** A name the composer can map back to a pubkey when `@Name` is sent. */
+export type MentionRecord = {
+  name: string;
+  pubkey: string;
+  isAgent: boolean;
+};
+
+function escapeRegExp(value: string): string {
+  return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+}
+
+/**
+ * Records whose `@Name` still appears in the text at send time — accepting
+ * a suggestion only counts if the mention survived editing. Longest names
+ * match first and consume their span, so `@amp` never claims a mention of
+ * `@amp (local)`. Boundaries mirror `withAgentMention`: the `@` must open a
+ * word (so `email@example.com` is not a mention).
+ */
+export function extractMentions(
+  text: string,
+  records: readonly MentionRecord[],
+): MentionRecord[] {
+  const found: MentionRecord[] = [];
+  const seenPubkeys = new Set<string>();
+  const ordered = [...records]
+    .filter((record) => record.name)
+    .sort((left, right) => right.name.length - left.name.length);
+  let remaining = text;
+  for (const record of ordered) {
+    const pattern = new RegExp(
+      `(^|[\\s([{])@${escapeRegExp(record.name)}(?=$|[\\s,.;:!?)\\]}])`,
+      "gi",
+    );
+    if (!pattern.test(remaining)) continue;
+    remaining = remaining.replace(pattern, "$1");
+    const pubkey = record.pubkey.toLowerCase();
+    if (seenPubkeys.has(pubkey)) continue;
+    seenPubkeys.add(pubkey);
+    found.push(record);
+  }
+  return found;
+}
diff --git a/desktop/src/features/dev-mode/lib/messageReactions.ts b/desktop/src/features/dev-mode/lib/messageReactions.ts
new file mode 100644
index 0000000000..8411034a09
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/messageReactions.ts
@@ -0,0 +1,50 @@
+import type { RelayEvent } from "@/shared/api/types";
+import { KIND_REACTION } from "@/shared/constants/kinds";
+
+const HEX_RE = /^[0-9a-f]+$/i;
+
+function reactionTargetId(tags: string[][]): string | null {
+  for (let index = tags.length - 1; index >= 0; index -= 1) {
+    const tag = tags[index];
+    if (
+      tag?.[0] === "e" &&
+      typeof tag[1] === "string" &&
+      tag[1].length === 64 &&
+      HEX_RE.test(tag[1])
+    ) {
+      return tag[1];
+    }
+  }
+  return null;
+}
+
+export type MessageReaction = {
+  emoji: string;
+  /** Who reacted — names the reactor in the chip's hover tooltip. */
+  pubkey: string;
+};
+
+/**
+ * Aggregate kind-7 reaction events by target message. Agents react to a
+ * prompt while working on it, so these chips double as the loading state.
+ */
+export function collectReactions(
+  events: RelayEvent[] | undefined,
+): Map<string, MessageReaction[]> {
+  const byTarget = new Map<string, MessageReaction[]>();
+  for (const event of events ?? []) {
+    if (event.kind !== KIND_REACTION) continue;
+    const targetId = reactionTargetId(event.tags);
+    if (!targetId) continue;
+    const raw = event.content.trim();
+    const emoji = raw === "" || raw === "+" ? "👍" : raw;
+    const reaction = { emoji, pubkey: event.pubkey };
+    const bucket = byTarget.get(targetId);
+    if (bucket) {
+      bucket.push(reaction);
+    } else {
+      byTarget.set(targetId, [reaction]);
+    }
+  }
+  return byTarget;
+}
diff --git a/desktop/src/features/dev-mode/lib/pinnedChannels.ts b/desktop/src/features/dev-mode/lib/pinnedChannels.ts
new file mode 100644
index 0000000000..a9d2b977e4
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/pinnedChannels.ts
@@ -0,0 +1,99 @@
+import * as React from "react";
+
+import type { Channel } from "@/shared/api/types";
+
+/**
+ * Device-local pinned channels for the developer-mode channel list. Channels
+ * have no pin field in the protocol, so the set lives in localStorage.
+ * Pinned channels render in their own section above everything else; both
+ * sections order by last activity, most recent first.
+ */
+
+const STORAGE_KEY = "buzz.devMode.pinnedChannels";
+
+const listeners = new Set<() => void>();
+
+let pinned = readStoredPinned();
+
+function readStoredPinned(): ReadonlySet<string> {
+  try {
+    const raw = globalThis.localStorage?.getItem(STORAGE_KEY);
+    if (!raw) return new Set();
+    const parsed: unknown = JSON.parse(raw);
+    if (!Array.isArray(parsed)) return new Set();
+    return new Set(parsed.filter((id): id is string => typeof id === "string"));
+  } catch {
+    return new Set();
+  }
+}
+
+function writePinned(next: ReadonlySet<string>) {
+  pinned = next;
+  try {
+    globalThis.localStorage?.setItem(STORAGE_KEY, JSON.stringify([...next]));
+  } catch {
+    // Persistence is best-effort; the in-memory value still applies.
+  }
+  for (const listener of listeners) {
+    listener();
+  }
+}
+
+function subscribe(listener: () => void): () => void {
+  listeners.add(listener);
+  return () => {
+    listeners.delete(listener);
+  };
+}
+
+function getSnapshot(): ReadonlySet<string> {
+  return pinned;
+}
+
+export function usePinnedChannels(): ReadonlySet<string> {
+  return React.useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+}
+
+export function toggleChannelPinned(channelId: string): void {
+  const next = new Set(pinned);
+  if (!next.delete(channelId)) {
+    next.add(channelId);
+  }
+  writePinned(next);
+}
+
+export type ChannelGroup = {
+  pinned: boolean;
+  channels: Channel[];
+};
+
+function byLastActivityDesc(left: Channel, right: Channel): number {
+  return (right.lastMessageAt ?? "").localeCompare(left.lastMessageAt ?? "");
+}
+
+/**
+ * Split channels into a pinned section on top and the rest beneath, each
+ * ordered by last activity (most recent first). `flat` matches render order
+ * for keyboard navigation.
+ */
+export function groupSessionChannels(
+  channels: Channel[],
+  pinnedIds: ReadonlySet<string>,
+): { groups: ChannelGroup[]; flat: Channel[] } {
+  const pinnedChannels: Channel[] = [];
+  const rest: Channel[] = [];
+  for (const channel of channels) {
+    (pinnedIds.has(channel.id) ? pinnedChannels : rest).push(channel);
+  }
+  pinnedChannels.sort(byLastActivityDesc);
+  rest.sort(byLastActivityDesc);
+
+  const groups: ChannelGroup[] = [];
+  if (pinnedChannels.length > 0) {
+    groups.push({ pinned: true, channels: pinnedChannels });
+  }
+  if (rest.length > 0 || groups.length === 0) {
+    groups.push({ pinned: false, channels: rest });
+  }
+  return { groups, flat: groups.flatMap((group) => group.channels) };
+}
diff --git a/desktop/src/features/dev-mode/lib/sessionNaming.test.mjs b/desktop/src/features/dev-mode/lib/sessionNaming.test.mjs
new file mode 100644
index 0000000000..25c04434e0
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/sessionNaming.test.mjs
@@ -0,0 +1,50 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { sanitizeChannelName, uniqueChannelName } from "./sessionNaming.ts";
+
+test("sanitizeChannelName_buildsHyphenatedNameFromWords", () => {
+  assert.equal(
+    sanitizeChannelName("Fix the login race condition"),
+    "fix-the-login-race-condition",
+  );
+});
+
+test("sanitizeChannelName_stripsPunctuationAndNormalizesCase", () => {
+  assert.equal(
+    sanitizeChannelName("Why is CI broken?! (again)"),
+    "why-is-ci-broken-again",
+  );
+});
+
+test("sanitizeChannelName_capsLengthAtWordBoundary", () => {
+  const name = sanitizeChannelName(
+    "one two three four five six seven eight nine ten eleven twelve",
+  );
+  assert.ok(name.length <= 40, `expected <= 40 chars, got ${name.length}`);
+  assert.ok(!name.endsWith("-"), "must not end mid-separator");
+});
+
+test("sanitizeChannelName_truncatesSingleOversizedWord", () => {
+  assert.equal(sanitizeChannelName("a".repeat(100)), "a".repeat(40));
+});
+
+test("sanitizeChannelName_neverEmitsDoubleHyphen", () => {
+  assert.equal(sanitizeChannelName("foo--bar"), "foo-bar");
+  assert.equal(sanitizeChannelName("foo - bar"), "foo-bar");
+  assert.equal(sanitizeChannelName("a -- b -- c"), "a-b-c");
+});
+
+test("sanitizeChannelName_emptyForSymbolOnlyInput", () => {
+  assert.equal(sanitizeChannelName(""), "");
+  assert.equal(sanitizeChannelName("!!! ???"), "");
+});
+
+test("uniqueChannelName_returnsBaseWhenFree", () => {
+  assert.equal(uniqueChannelName("fix-login", new Set()), "fix-login");
+});
+
+test("uniqueChannelName_suffixesUntilNameIsUnique", () => {
+  const existing = new Set(["fix-login", "fix-login-2"]);
+  assert.equal(uniqueChannelName("fix-login", existing), "fix-login-3");
+});
diff --git a/desktop/src/features/dev-mode/lib/sessionNaming.ts b/desktop/src/features/dev-mode/lib/sessionNaming.ts
new file mode 100644
index 0000000000..867686ebee
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/sessionNaming.ts
@@ -0,0 +1,33 @@
+const MAX_SLUG_LENGTH = 40;
+
+/**
+ * Reduce arbitrary text to channel-name form: lowercase kebab-case.
+ * Splitting on hyphens as well as whitespace guarantees the result never
+ * contains `--`, which would make it parse as a sub-channel name
+ * (see subChannels.ts).
+ */
+export function sanitizeChannelName(text: string): string {
+  return text
+    .toLowerCase()
+    .replace(/[^a-z0-9\s-]/g, "")
+    .trim()
+    .split(/[\s-]+/)
+    .reduce((slug, word) => {
+      if (word.length === 0) return slug;
+      if (slug.length === 0) return word.slice(0, MAX_SLUG_LENGTH);
+      const next = `${slug}-${word}`;
+      return next.length > MAX_SLUG_LENGTH ? slug : next;
+    }, "");
+}
+
+/** Suffix a base name until it does not collide with an existing channel. */
+export function uniqueChannelName(
+  base: string,
+  existingNames: ReadonlySet<string>,
+): string {
+  if (!existingNames.has(base)) return base;
+  for (let suffix = 2; ; suffix += 1) {
+    const candidate = `${base}-${suffix}`;
+    if (!existingNames.has(candidate)) return candidate;
+  }
+}
diff --git a/desktop/src/features/dev-mode/lib/subChannels.test.mjs b/desktop/src/features/dev-mode/lib/subChannels.test.mjs
new file mode 100644
index 0000000000..60403feab7
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/subChannels.test.mjs
@@ -0,0 +1,196 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  aggregateLastActivity,
+  aggregateUnreadMains,
+  appendSubChannelToParentCanvas,
+  applySubChannelRenames,
+  indexSubChannels,
+  parseSubChannelName,
+  planSubChannelRenames,
+  subChannelAnnouncement,
+  subChannelCanvasDoc,
+  subChannelName,
+} from "./subChannels.ts";
+
+function channel(id, name, lastMessageAt = null) {
+  return { id, name, lastMessageAt };
+}
+
+test("parseSubChannelName_splitsOnFirstDoubleHyphen", () => {
+  assert.deepEqual(parseSubChannelName("deploy-fixes--flaky-ci"), {
+    parentName: "deploy-fixes",
+    subSlug: "flaky-ci",
+  });
+});
+
+test("parseSubChannelName_rejectsPlainNames", () => {
+  assert.equal(parseSubChannelName("deploy-fixes"), null);
+  assert.equal(parseSubChannelName("deploy-fixes-ci"), null);
+});
+
+test("parseSubChannelName_rejectsEmptyComponents", () => {
+  assert.equal(parseSubChannelName("--sub"), null);
+  assert.equal(parseSubChannelName("parent--"), null);
+});
+
+test("parseSubChannelName_nestedNameParsesAsChildOfFirstParent", () => {
+  // `a--b--c` splits at the first separator; `a--b` is not a valid parent
+  // name for indexing purposes, so it stays an orphan unless `a` exists.
+  assert.deepEqual(parseSubChannelName("a--b--c"), {
+    parentName: "a",
+    subSlug: "b--c",
+  });
+});
+
+test("subChannelName_roundTripsWithParse", () => {
+  const name = subChannelName("deploy-fixes", "rollback-plan");
+  assert.equal(name, "deploy-fixes--rollback-plan");
+  assert.deepEqual(parseSubChannelName(name), {
+    parentName: "deploy-fixes",
+    subSlug: "rollback-plan",
+  });
+});
+
+test("indexSubChannels_pairsSubsWithParents", () => {
+  const parent = channel("p1", "deploy-fixes");
+  const subA = channel("c1", "deploy-fixes--flaky-ci");
+  const subB = channel("c2", "deploy-fixes--rollback");
+  const other = channel("p2", "general");
+  const index = indexSubChannels([subB, parent, other, subA]);
+
+  assert.deepEqual(
+    index.mains.map((c) => c.id),
+    ["p1", "p2"],
+  );
+  assert.deepEqual(
+    index.subsByParentId.get("p1").map((c) => c.name),
+    ["deploy-fixes--flaky-ci", "deploy-fixes--rollback"],
+  );
+  assert.equal(index.parentIdByChildId.get("c1"), "p1");
+  assert.equal(index.parentIdByChildId.get("c2"), "p1");
+});
+
+test("indexSubChannels_orphanSubStaysVisibleAsMain", () => {
+  const index = indexSubChannels([channel("c1", "ghost--task")]);
+  assert.deepEqual(
+    index.mains.map((c) => c.id),
+    ["c1"],
+  );
+  assert.equal(index.subsByParentId.size, 0);
+});
+
+test("indexSubChannels_handlesHundredsOfSubsInOnePass", () => {
+  const channels = [channel("p", "work")];
+  for (let i = 0; i < 500; i += 1) {
+    channels.push(channel(`c${i}`, `work--task-${String(i).padStart(3, "0")}`));
+  }
+  const index = indexSubChannels(channels);
+  assert.equal(index.mains.length, 1);
+  assert.equal(index.subsByParentId.get("p").length, 500);
+  assert.equal(index.subsByParentId.get("p")[0].name, "work--task-000");
+});
+
+test("aggregateUnreadMains_bubblesSubUnreadToParent", () => {
+  const index = indexSubChannels([
+    channel("p1", "work"),
+    channel("c1", "work--api"),
+    channel("p2", "general"),
+  ]);
+  const unread = aggregateUnreadMains(index, new Set(["c1"]));
+  assert.deepEqual([...unread], ["p1"]);
+});
+
+test("aggregateLastActivity_usesLatestSubTimestamp", () => {
+  const index = indexSubChannels([
+    channel("p1", "work", "2026-07-01T00:00:00Z"),
+    channel("c1", "work--api", "2026-07-20T00:00:00Z"),
+    channel("c2", "work--ui", "2026-07-10T00:00:00Z"),
+  ]);
+  const overrides = aggregateLastActivity(index);
+  assert.equal(overrides.get("p1"), "2026-07-20T00:00:00Z");
+});
+
+test("subChannelAnnouncement_matchesCliFormat", () => {
+  assert.equal(subChannelAnnouncement("work--api"), "→ spawned #work--api");
+});
+
+test("subChannelCanvasDoc_recordsParentAndReportBackContract", () => {
+  const doc = subChannelCanvasDoc({
+    parentName: "work",
+    parentId: "uuid-1",
+    announcementEventId: "event-1",
+    task: "Build the API",
+  });
+  assert.match(doc, /# Sub-channel of #work/);
+  assert.match(doc, /- parent: #work \(uuid-1\)/);
+  assert.match(doc, /- spawned-from: event-1/);
+  assert.match(doc, /- task: Build the API/);
+  assert.match(doc, /thread reply to the spawn announcement/);
+});
+
+test("appendSubChannelToParentCanvas_createsSectionWhenMissing", () => {
+  assert.equal(
+    appendSubChannelToParentCanvas(null, "work--api", "Build API"),
+    "## Sub-channels\n- #work--api — Build API\n",
+  );
+  assert.equal(
+    appendSubChannelToParentCanvas("# Work", "work--api", "Build API"),
+    "# Work\n\n## Sub-channels\n- #work--api — Build API\n",
+  );
+});
+
+test("appendSubChannelToParentCanvas_appendsAfterExistingBullets", () => {
+  const canvas =
+    "# Work\n\n## Sub-channels\n- #work--one — One\n\nNotes\n\n## Links\n- link";
+  assert.equal(
+    appendSubChannelToParentCanvas(canvas, "work--two", "Two"),
+    "# Work\n\n## Sub-channels\n- #work--one — One\n- #work--two — Two\n\nNotes\n\n## Links\n- link",
+  );
+});
+
+test("planSubChannelRenames_rewritesEveryChildPrefix", () => {
+  const channels = [
+    channel("p", "work"),
+    channel("c1", "work--api"),
+    channel("c2", "work--ui"),
+    channel("x", "workshop--misc"),
+  ];
+  assert.deepEqual(planSubChannelRenames(channels, "work", "platform"), [
+    { channelId: "c1", newName: "platform--api" },
+    { channelId: "c2", newName: "platform--ui" },
+  ]);
+});
+
+test("planSubChannelRenames_noOpWhenNameUnchanged", () => {
+  assert.deepEqual(
+    planSubChannelRenames([channel("c1", "work--api")], "work", "work"),
+    [],
+  );
+});
+
+test("applySubChannelRenames_boundsConcurrencyAndCollectsFailures", async () => {
+  const renames = Array.from({ length: 40 }, (_, i) => ({
+    channelId: `c${i}`,
+    newName: `next--task-${i}`,
+  }));
+  let inFlight = 0;
+  let peak = 0;
+  const { failed } = await applySubChannelRenames(
+    renames,
+    async (channelId) => {
+      inFlight += 1;
+      peak = Math.max(peak, inFlight);
+      await new Promise((resolve) => setTimeout(resolve, 1));
+      inFlight -= 1;
+      if (channelId === "c7") throw new Error("boom");
+    },
+    4,
+  );
+  assert.ok(peak <= 4, `expected concurrency <= 4, saw ${peak}`);
+  assert.deepEqual(
+    failed.map((f) => f.channelId),
+    ["c7"],
+  );
+});
diff --git a/desktop/src/features/dev-mode/lib/subChannels.ts b/desktop/src/features/dev-mode/lib/subChannels.ts
new file mode 100644
index 0000000000..e2983910c2
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/subChannels.ts
@@ -0,0 +1,241 @@
+import type { Channel } from "@/shared/api/types";
+
+/**
+ * Sub-channels are a pure naming convention — no relay/schema support: a
+ * channel named `parent--sub` is a sub-channel of the channel named
+ * `parent`. One nesting level only. The separator can never appear in
+ * generated names (sanitizeChannelName collapses hyphen runs), so ordinary
+ * channels cannot accidentally become subs.
+ */
+export const SUB_CHANNEL_SEPARATOR = "--";
+
+export type SubChannelRef = {
+  parentName: string;
+  subSlug: string;
+};
+
+/** Parse `parent--sub`; null when the name is not sub-channel-shaped. */
+export function parseSubChannelName(name: string): SubChannelRef | null {
+  const index = name.indexOf(SUB_CHANNEL_SEPARATOR);
+  if (index <= 0) return null;
+  const subSlug = name.slice(index + SUB_CHANNEL_SEPARATOR.length);
+  if (subSlug.length === 0) return null;
+  return { parentName: name.slice(0, index), subSlug };
+}
+
+export function subChannelName(parentName: string, subSlug: string): string {
+  return `${parentName}${SUB_CHANNEL_SEPARATOR}${subSlug}`;
+}
+
+export type SubChannelIndex = {
+  /** Channels that render in the left list: everything except paired subs. */
+  mains: Channel[];
+  /** Sub-channels per parent id, sorted by name for stable tab order. */
+  subsByParentId: ReadonlyMap<string, Channel[]>;
+  parentIdByChildId: ReadonlyMap<string, string>;
+};
+
+/**
+ * Pair subs with their parents in one O(n) pass — parents can have hundreds
+ * of subs, so no per-channel scans. A `--` name whose parent is not in the
+ * list stays a main (nothing silently disappears).
+ */
+export function indexSubChannels(channels: Channel[]): SubChannelIndex {
+  const byName = new Map<string, Channel>();
+  for (const channel of channels) {
+    byName.set(channel.name, channel);
+  }
+
+  const mains: Channel[] = [];
+  const subsByParentId = new Map<string, Channel[]>();
+  const parentIdByChildId = new Map<string, string>();
+  for (const channel of channels) {
+    const parsed = parseSubChannelName(channel.name);
+    const parent = parsed ? byName.get(parsed.parentName) : undefined;
+    if (!parsed || !parent || parent.id === channel.id) {
+      mains.push(channel);
+      continue;
+    }
+    parentIdByChildId.set(channel.id, parent.id);
+    const siblings = subsByParentId.get(parent.id);
+    if (siblings) {
+      siblings.push(channel);
+    } else {
+      subsByParentId.set(parent.id, [channel]);
+    }
+  }
+  for (const siblings of subsByParentId.values()) {
+    siblings.sort((left, right) => left.name.localeCompare(right.name));
+  }
+  return { mains, subsByParentId, parentIdByChildId };
+}
+
+/**
+ * Unread mains for the left list: a main is unread when it or any of its
+ * subs is unread — subs have no row of their own to carry the dot.
+ */
+export function aggregateUnreadMains(
+  index: SubChannelIndex,
+  unreadChannelIds: ReadonlySet<string>,
+): ReadonlySet<string> {
+  const unread = new Set<string>();
+  for (const main of index.mains) {
+    if (unreadChannelIds.has(main.id)) {
+      unread.add(main.id);
+      continue;
+    }
+    const subs = index.subsByParentId.get(main.id);
+    if (subs?.some((sub) => unreadChannelIds.has(sub.id))) {
+      unread.add(main.id);
+    }
+  }
+  return unread;
+}
+
+/**
+ * Last-activity overrides for list ordering: a main's activity is the max
+ * of its own and all its subs', so working sub-channels float their parent.
+ */
+export function aggregateLastActivity(
+  index: SubChannelIndex,
+): ReadonlyMap<string, string> {
+  const overrides = new Map<string, string>();
+  for (const [parentId, subs] of index.subsByParentId) {
+    let latest = "";
+    for (const sub of subs) {
+      if ((sub.lastMessageAt ?? "") > latest) {
+        latest = sub.lastMessageAt ?? "";
+      }
+    }
+    if (latest.length > 0) {
+      overrides.set(parentId, latest);
+    }
+  }
+  return overrides;
+}
+
+/** First line of the prompt, bounded — used in announcements and canvases. */
+export function subChannelTaskLine(task: string): string {
+  const firstLine = task.split("\n", 1)[0].trim();
+  return firstLine.length > 140 ? `${firstLine.slice(0, 139)}…` : firstLine;
+}
+
+export function subChannelAnnouncement(subName: string): string {
+  return `→ spawned #${subName}`;
+}
+
+/**
+ * The sub-channel's canvas records its relationship and the report-back
+ * contract. Format is shared with `buzz channels create --parent` — keep
+ * the two in sync (crates/buzz-cli/src/commands/channels.rs).
+ */
+export function subChannelCanvasDoc(input: {
+  parentName: string;
+  parentId: string;
+  announcementEventId: string;
+  task: string;
+}): string {
+  const task = subChannelTaskLine(input.task);
+  return [
+    `# Sub-channel of #${input.parentName}`,
+    "",
+    `- parent: #${input.parentName} (${input.parentId})`,
+    `- spawned-from: ${input.announcementEventId}`,
+    `- task: ${task}`,
+    "",
+    `When the work here is complete, post a summary to #${input.parentName} ` +
+      `as a thread reply to the spawn announcement (event ${input.announcementEventId}). ` +
+      `Every member of this sub-channel must be a member of #${input.parentName}.`,
+  ].join("\n");
+}
+
+const SUB_CHANNELS_HEADING = "## Sub-channels";
+
+/**
+ * Append a sub entry to the parent canvas's `## Sub-channels` section,
+ * creating the section (and canvas) when absent. Single read + single write
+ * even with hundreds of entries. Same format as the CLI's --parent path.
+ */
+export function appendSubChannelToParentCanvas(
+  existing: string | null,
+  subName: string,
+  task: string,
+): string {
+  const bullet = `- #${subName} — ${subChannelTaskLine(task)}`;
+  const canvas = existing ?? "";
+  const lines = canvas.split("\n");
+  const headingAt = lines.findIndex(
+    (line) => line.trim() === SUB_CHANNELS_HEADING,
+  );
+  if (headingAt === -1) {
+    const base = canvas.trimEnd();
+    return base.length === 0
+      ? `${SUB_CHANNELS_HEADING}\n${bullet}\n`
+      : `${base}\n\n${SUB_CHANNELS_HEADING}\n${bullet}\n`;
+  }
+  let insertAt = headingAt + 1;
+  for (let index = headingAt + 1; index < lines.length; index += 1) {
+    const line = lines[index];
+    if (line.trim().length === 0) continue;
+    if (!line.startsWith("- ")) break;
+    insertAt = index + 1;
+  }
+  lines.splice(insertAt, 0, bullet);
+  return lines.join("\n");
+}
+
+export type SubChannelRename = {
+  channelId: string;
+  newName: string;
+};
+
+/**
+ * Renaming a parent must rename every sub (the name IS the link). Pure
+ * planner: single pass over the channel list; the caller applies the
+ * updates with bounded concurrency.
+ */
+export function planSubChannelRenames(
+  channels: readonly Pick<Channel, "id" | "name">[],
+  oldParentName: string,
+  newParentName: string,
+): SubChannelRename[] {
+  if (oldParentName === newParentName) return [];
+  const prefix = `${oldParentName}${SUB_CHANNEL_SEPARATOR}`;
+  const renames: SubChannelRename[] = [];
+  for (const channel of channels) {
+    if (!channel.name.startsWith(prefix)) continue;
+    const subSlug = channel.name.slice(prefix.length);
+    if (subSlug.length === 0) continue;
+    renames.push({
+      channelId: channel.id,
+      newName: subChannelName(newParentName, subSlug),
+    });
+  }
+  return renames;
+}
+
+/** Apply rename plans with bounded concurrency; failures are collected. */
+export async function applySubChannelRenames(
+  renames: readonly SubChannelRename[],
+  rename: (channelId: string, newName: string) => Promise<void>,
+  concurrency = 8,
+): Promise<{ failed: SubChannelRename[] }> {
+  const failed: SubChannelRename[] = [];
+  let next = 0;
+  const workers = Array.from(
+    { length: Math.min(concurrency, renames.length) },
+    async () => {
+      while (next < renames.length) {
+        const plan = renames[next];
+        next += 1;
+        try {
+          await rename(plan.channelId, plan.newName);
+        } catch {
+          failed.push(plan);
+        }
+      }
+    },
+  );
+  await Promise.all(workers);
+  return { failed };
+}
diff --git a/desktop/src/features/dev-mode/lib/transcriptRoots.test.mjs b/desktop/src/features/dev-mode/lib/transcriptRoots.test.mjs
new file mode 100644
index 0000000000..4b0ace79bc
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/transcriptRoots.test.mjs
@@ -0,0 +1,32 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { selectInlineVisibleCount } from "./transcriptRoots.ts";
+
+const AGENT = "agent-pubkey";
+const HUMAN = "human-pubkey";
+
+function reply(pubkey) {
+  return { pubkey };
+}
+
+const isAgent = (pubkey) => pubkey === AGENT;
+
+test("selectInlineVisibleCount_showsTheWholeLeadingAgentRun", () => {
+  const replies = [reply(AGENT), reply(AGENT), reply(AGENT)];
+  assert.equal(selectInlineVisibleCount(replies, isAgent), 3);
+});
+
+test("selectInlineVisibleCount_collapsesFromTheFirstHumanReply", () => {
+  const replies = [reply(AGENT), reply(AGENT), reply(HUMAN), reply(AGENT)];
+  assert.equal(selectInlineVisibleCount(replies, isAgent), 2);
+});
+
+test("selectInlineVisibleCount_humanFirstThreadStillShowsItsFirstReply", () => {
+  const replies = [reply(HUMAN), reply(AGENT)];
+  assert.equal(selectInlineVisibleCount(replies, isAgent), 1);
+});
+
+test("selectInlineVisibleCount_emptyThreadShowsNothing", () => {
+  assert.equal(selectInlineVisibleCount([], isAgent), 0);
+});
diff --git a/desktop/src/features/dev-mode/lib/transcriptRoots.ts b/desktop/src/features/dev-mode/lib/transcriptRoots.ts
new file mode 100644
index 0000000000..53d1f60343
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/transcriptRoots.ts
@@ -0,0 +1,50 @@
+import { isThreadReply } from "@/features/messages/lib/threading";
+import type { RelayEvent } from "@/shared/api/types";
+import {
+  KIND_STREAM_MESSAGE,
+  KIND_STREAM_MESSAGE_V2,
+} from "@/shared/constants/kinds";
+
+export const DEV_MESSAGE_KINDS = new Set([
+  KIND_STREAM_MESSAGE,
+  KIND_STREAM_MESSAGE_V2,
+]);
+
+export function byCreatedAscending(left: RelayEvent, right: RelayEvent) {
+  return left.created_at !== right.created_at
+    ? left.created_at - right.created_at
+    : left.id < right.id
+      ? -1
+      : 1;
+}
+
+/**
+ * How many of a thread's ordered replies render inline in the main chat
+ * view: the whole leading run of agent replies — collapsing starts at the
+ * first human response. A human-first thread still shows its first reply
+ * inline. Shared by the transcript renderer and unread routing so "would
+ * this reply be visible without opening the thread" has one answer.
+ */
+export function selectInlineVisibleCount(
+  orderedReplies: readonly RelayEvent[],
+  isAgent: (pubkey: string) => boolean,
+): number {
+  let end = 0;
+  while (end < orderedReplies.length && isAgent(orderedReplies[end].pubkey)) {
+    end += 1;
+  }
+  if (end === 0 && orderedReplies.length > 0) end = 1;
+  return end;
+}
+
+/** Top-level prompt messages of a channel, oldest first. */
+export function selectRootEvents(
+  events: RelayEvent[] | undefined,
+): RelayEvent[] {
+  return (events ?? [])
+    .filter(
+      (event) =>
+        DEV_MESSAGE_KINDS.has(event.kind) && !isThreadReply(event.tags),
+    )
+    .sort(byCreatedAscending);
+}
diff --git a/desktop/src/features/dev-mode/lib/unreadThreads.test.mjs b/desktop/src/features/dev-mode/lib/unreadThreads.test.mjs
new file mode 100644
index 0000000000..33576d3079
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/unreadThreads.test.mjs
@@ -0,0 +1,115 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  findUnreadFamilyTarget,
+  selectUnreadThreadRoots,
+} from "./unreadThreads.ts";
+
+function summary(lastReplyAt) {
+  return {
+    replyCount: 1,
+    descendantCount: 1,
+    lastReplyAt,
+    participantPubkeys: [],
+  };
+}
+
+function replyItem(channelId, rootId, createdAt) {
+  return {
+    channelId,
+    createdAt,
+    tags: [
+      ["e", rootId, "", "root"],
+      ["e", rootId, "", "reply"],
+    ],
+  };
+}
+
+test("selectUnreadThreadRoots_flagsRepliesPastTheReadFrontier", () => {
+  const summaries = new Map([
+    ["seen", summary(100)],
+    ["unseen", summary(200)],
+    ["never-read", summary(50)],
+    ["no-replies", summary(null)],
+  ]);
+  const readAts = new Map([
+    ["seen", 100],
+    ["unseen", 150],
+  ]);
+  const unread = selectUnreadThreadRoots(
+    summaries,
+    (rootId) => readAts.get(rootId) ?? null,
+  );
+  assert.deepEqual([...unread].sort(), ["never-read", "unseen"]);
+});
+
+test("findUnreadFamilyTarget_picksTheNewestUnreadThreadAcrossTheFamily", () => {
+  const target = findUnreadFamilyTarget({
+    familyChannelIds: ["main", "sub-a", "sub-b"],
+    unreadChannelIds: new Set(["sub-a", "sub-b"]),
+    topLevelUnreadChannelIds: new Set(),
+    threadActivity: [
+      replyItem("sub-a", "root-1", 100),
+      replyItem("sub-b", "root-2", 300),
+      replyItem("elsewhere", "root-3", 900),
+    ],
+    getThreadReadAt: () => null,
+  });
+  assert.deepEqual(target, { channelId: "sub-b", rootId: "root-2" });
+});
+
+test("findUnreadFamilyTarget_skipsRepliesAlreadyRead", () => {
+  const target = findUnreadFamilyTarget({
+    familyChannelIds: ["main"],
+    unreadChannelIds: new Set(["main"]),
+    topLevelUnreadChannelIds: new Set(),
+    threadActivity: [replyItem("main", "root-1", 100)],
+    getThreadReadAt: () => 100,
+  });
+  assert.equal(target, null);
+});
+
+test("findUnreadFamilyTarget_skipsChannelsTheSharedModelConsidersRead", () => {
+  const target = findUnreadFamilyTarget({
+    familyChannelIds: ["main", "sub-a"],
+    unreadChannelIds: new Set(),
+    topLevelUnreadChannelIds: new Set(),
+    threadActivity: [replyItem("sub-a", "root-1", 100)],
+    getThreadReadAt: () => null,
+  });
+  assert.equal(target, null);
+});
+
+test("findUnreadFamilyTarget_fallsBackToTopLevelUnreadMainFirst", () => {
+  const target = findUnreadFamilyTarget({
+    familyChannelIds: ["main", "sub-a", "sub-b"],
+    unreadChannelIds: new Set(["main", "sub-b"]),
+    topLevelUnreadChannelIds: new Set(["sub-b", "main"]),
+    threadActivity: [],
+    getThreadReadAt: () => null,
+  });
+  assert.deepEqual(target, { channelId: "main", rootId: null });
+});
+
+test("findUnreadFamilyTarget_threadReplyOutranksTopLevelUnread", () => {
+  const target = findUnreadFamilyTarget({
+    familyChannelIds: ["main", "sub-a"],
+    unreadChannelIds: new Set(["main", "sub-a"]),
+    topLevelUnreadChannelIds: new Set(["main"]),
+    threadActivity: [replyItem("sub-a", "root-1", 100)],
+    getThreadReadAt: () => null,
+  });
+  assert.deepEqual(target, { channelId: "sub-a", rootId: "root-1" });
+});
+
+test("findUnreadFamilyTarget_returnsNullWhenNothingIsUnread", () => {
+  const target = findUnreadFamilyTarget({
+    familyChannelIds: ["main"],
+    unreadChannelIds: new Set(),
+    topLevelUnreadChannelIds: new Set(),
+    threadActivity: [],
+    getThreadReadAt: () => null,
+  });
+  assert.equal(target, null);
+});
diff --git a/desktop/src/features/dev-mode/lib/unreadThreads.ts b/desktop/src/features/dev-mode/lib/unreadThreads.ts
new file mode 100644
index 0000000000..cf5c798336
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/unreadThreads.ts
@@ -0,0 +1,83 @@
+import type { ChannelWindowThreadSummary } from "@/features/messages/lib/channelWindowStore";
+import { getThreadReference } from "@/features/messages/lib/threading";
+
+/**
+ * Roots whose thread has replies past the shared read frontier. Built from
+ * the same window summaries the transcript renders reply counts from, so
+ * the per-card unread dot always agrees with what is on screen.
+ */
+export function selectUnreadThreadRoots(
+  summaries: ReadonlyMap<string, ChannelWindowThreadSummary>,
+  getThreadReadAt: (rootId: string) => number | null,
+): ReadonlySet<string> {
+  const unread = new Set<string>();
+  for (const [rootId, summary] of summaries) {
+    if (!summary.lastReplyAt) continue;
+    const readAt = getThreadReadAt(rootId);
+    if (readAt === null || summary.lastReplyAt > readAt) {
+      unread.add(rootId);
+    }
+  }
+  return unread;
+}
+
+export type UnreadFamilyTarget = {
+  channelId: string;
+  /**
+   * The unread thread needing attention, or null for a top-level unread.
+   * Routing opens its side chat only when the unread replies are collapsed
+   * in the main view (see useUnreadRouting) — inline unread replies are
+   * read just by looking at the channel.
+   */
+  rootId: string | null;
+};
+
+/**
+ * Where opening an unread channel family should land: the newest unread
+ * thread reply anywhere in the family (main + tabs) wins — that is the
+ * agent chat needing attention — falling back to the first family channel
+ * (main first) with an unread top-level post. Null means nothing unread,
+ * so the caller opens the channel it was asked for.
+ *
+ * Thread activity is the shared observed-events feed (bounded, newest
+ * ~100), already gated to threads relevant to the user; family membership
+ * is checked via a Set so hundreds of tabs stay cheap.
+ */
+export function findUnreadFamilyTarget(input: {
+  /** Main channel id first, then its sub-channel (tab) ids. */
+  familyChannelIds: readonly string[];
+  unreadChannelIds: ReadonlySet<string>;
+  topLevelUnreadChannelIds: ReadonlySet<string>;
+  threadActivity: readonly {
+    channelId: string;
+    createdAt: number;
+    tags: string[][];
+  }[];
+  getThreadReadAt: (rootId: string, channelId: string) => number | null;
+}): UnreadFamilyTarget | null {
+  const family = new Set(input.familyChannelIds);
+  let best: { channelId: string; rootId: string; createdAt: number } | null =
+    null;
+  for (const item of input.threadActivity) {
+    if (!family.has(item.channelId)) continue;
+    // Channel-level gate keeps routing consistent with the visible dot —
+    // the shared model has already folded read markers for cleared channels.
+    if (!input.unreadChannelIds.has(item.channelId)) continue;
+    const rootId = getThreadReference(item.tags).rootId;
+    if (rootId === null) continue;
+    const readAt = input.getThreadReadAt(rootId, item.channelId);
+    if (readAt !== null && item.createdAt <= readAt) continue;
+    if (!best || item.createdAt > best.createdAt) {
+      best = { channelId: item.channelId, rootId, createdAt: item.createdAt };
+    }
+  }
+  if (best) {
+    return { channelId: best.channelId, rootId: best.rootId };
+  }
+  for (const channelId of input.familyChannelIds) {
+    if (input.topLevelUnreadChannelIds.has(channelId)) {
+      return { channelId, rootId: null };
+    }
+  }
+  return null;
+}
diff --git a/desktop/src/features/dev-mode/lib/useChannelRefAutocomplete.ts b/desktop/src/features/dev-mode/lib/useChannelRefAutocomplete.ts
new file mode 100644
index 0000000000..2a7da1cd81
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useChannelRefAutocomplete.ts
@@ -0,0 +1,134 @@
+import * as React from "react";
+
+import {
+  type ChannelRef,
+  useChannelRefs,
+} from "@/features/dev-mode/lib/channelRefs";
+import { detectPrefixQuery } from "@/shared/lib/detectPrefixQuery";
+
+const MAX_SUGGESTIONS = 6;
+
+/**
+ * `#channel` autocomplete for a dev-mode composer textarea. Typing `#` plus
+ * a prefix at the caret opens suggestions; ↑/↓ move, Tab/Enter accept
+ * (inserting `#channel-name `), Escape dismisses. `handleKeyDown` returns
+ * true when it consumed the key, so callers try it before their own
+ * bindings (Tab normally cycles modes, Enter normally sends).
+ */
+export function useChannelRefAutocomplete({
+  value,
+  onChange,
+  textareaRef,
+}: {
+  value: string;
+  onChange: (value: string) => void;
+  textareaRef: React.RefObject<HTMLTextAreaElement | null>;
+}) {
+  const { channels } = useChannelRefs();
+  const [cursor, setCursor] = React.useState(0);
+  const [selectedIndex, setSelectedIndex] = React.useState(0);
+  const [dismissed, setDismissed] = React.useState(false);
+
+  const knownNamesLower = React.useMemo(
+    () => channels.map((channel) => channel.name.toLowerCase()),
+    [channels],
+  );
+
+  const detection = React.useMemo(
+    () => detectPrefixQuery("#", value, cursor, knownNamesLower),
+    [cursor, knownNamesLower, value],
+  );
+
+  const suggestions = React.useMemo<ChannelRef[]>(() => {
+    if (!detection) return [];
+    const needle = detection.query.toLowerCase();
+    const starts: ChannelRef[] = [];
+    const contains: ChannelRef[] = [];
+    for (const channel of channels) {
+      const name = channel.name.toLowerCase();
+      if (name.startsWith(needle)) {
+        starts.push(channel);
+      } else if (name.includes(needle)) {
+        contains.push(channel);
+      }
+    }
+    return [...starts, ...contains].slice(0, MAX_SUGGESTIONS);
+  }, [channels, detection]);
+
+  const open = !dismissed && suggestions.length > 0;
+
+  // A fresh query (typing/caret movement) clears the selection and any
+  // Escape dismissal from the previous query.
+  const queryKey = detection
+    ? `${detection.startIndex}:${detection.query}`
+    : null;
+  const previousQueryKeyRef = React.useRef(queryKey);
+  if (previousQueryKeyRef.current !== queryKey) {
+    previousQueryKeyRef.current = queryKey;
+    if (selectedIndex !== 0) setSelectedIndex(0);
+    if (dismissed) setDismissed(false);
+  }
+
+  const syncCursor = React.useCallback((target: HTMLTextAreaElement) => {
+    setCursor(target.selectionStart ?? target.value.length);
+  }, []);
+
+  const accept = React.useCallback(
+    (suggestion: ChannelRef) => {
+      if (!detection) return;
+      const before = value.slice(0, detection.startIndex);
+      const inserted = `#${suggestion.name} `;
+      const next = before + inserted + value.slice(cursor);
+      onChange(next);
+      const caret = before.length + inserted.length;
+      setCursor(caret);
+      requestAnimationFrame(() => {
+        const textarea = textareaRef.current;
+        // Skip if the user already typed past the accept — repositioning
+        // now would drop their keystrokes into the middle of the text.
+        if (!textarea || textarea.value !== next) return;
+        textarea.setSelectionRange(caret, caret);
+      });
+    },
+    [cursor, detection, onChange, textareaRef, value],
+  );
+
+  const handleKeyDown = React.useCallback(
+    (event: React.KeyboardEvent<HTMLTextAreaElement>): boolean => {
+      if (!open) return false;
+      // Modified keys belong to composer shortcuts (e.g. ⌥↑ channel step).
+      if (event.altKey || event.metaKey || event.ctrlKey) return false;
+      if (event.key === "ArrowUp" || event.key === "ArrowDown") {
+        event.preventDefault();
+        const delta = event.key === "ArrowUp" ? -1 : 1;
+        setSelectedIndex(
+          (current) =>
+            (current + delta + suggestions.length) % suggestions.length,
+        );
+        return true;
+      }
+      if (event.key === "Tab" || event.key === "Enter") {
+        event.preventDefault();
+        accept(suggestions[selectedIndex] ?? suggestions[0]);
+        return true;
+      }
+      if (event.key === "Escape") {
+        event.preventDefault();
+        setDismissed(true);
+        return true;
+      }
+      return false;
+    },
+    [accept, open, selectedIndex, suggestions],
+  );
+
+  return {
+    open,
+    suggestions,
+    selectedIndex,
+    query: detection?.query ?? "",
+    accept,
+    handleKeyDown,
+    syncCursor,
+  };
+}
diff --git a/desktop/src/features/dev-mode/lib/useComposerAutoGrow.ts b/desktop/src/features/dev-mode/lib/useComposerAutoGrow.ts
new file mode 100644
index 0000000000..f9e3cb7b33
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useComposerAutoGrow.ts
@@ -0,0 +1,127 @@
+import * as React from "react";
+
+/** One text line at `leading-6` — the composer's minimum height. */
+const LINE_PX = 24;
+
+/** Cap auto-growth so the transcript always stays visible. */
+function maxHeightPx(): number {
+  return Math.max(LINE_PX * 4, Math.floor(globalThis.innerHeight * 0.4));
+}
+
+function readStoredFloor(storageKey: string): number | null {
+  try {
+    const raw = globalThis.localStorage?.getItem(storageKey);
+    const value = raw === null || raw === undefined ? Number.NaN : Number(raw);
+    if (Number.isFinite(value) && value > LINE_PX) {
+      return value;
+    }
+  } catch {
+    // Fall through to content-sized.
+  }
+  return null;
+}
+
+/**
+ * Auto-grow a composer textarea upward with its content (wrapped lines
+ * included, unlike a newline-counting `rows`), capped at 40% of the window.
+ *
+ * A drag on the returned handle sets a persisted manual *floor*: the box
+ * never rests shorter than the floor, while content taller than it still
+ * grows the box up to the cap (then scrolls internally).
+ */
+export function useComposerAutoGrow(value: string, storageKey: string) {
+  const textareaRef = React.useRef<HTMLTextAreaElement>(null);
+  const [floor, setFloor] = React.useState<number | null>(() =>
+    readStoredFloor(storageKey),
+  );
+  const [dragging, setDragging] = React.useState(false);
+  const dragStart = React.useRef<{ y: number; floor: number } | null>(null);
+
+  // biome-ignore lint/correctness/useExhaustiveDependencies: value is the intentional resize trigger; the effect measures the DOM, not the string
+  React.useLayoutEffect(() => {
+    const el = textareaRef.current;
+    if (!el) return;
+    // Freeze the wrapper during the 0px measurement: shrinking the textarea
+    // momentarily reflows the flex siblings, and that reflow clamps the
+    // transcript's scrollTop — every keystroke would scroll the chat up.
+    const wrapper = el.parentElement;
+    const wrapperHeight = wrapper?.style.height ?? "";
+    if (wrapper) wrapper.style.height = `${wrapper.offsetHeight}px`;
+    el.style.height = "0px";
+    const max = maxHeightPx();
+    const target = Math.min(
+      Math.max(el.scrollHeight, floor ?? 0, LINE_PX),
+      max,
+    );
+    el.style.height = `${target}px`;
+    el.style.overflowY = el.scrollHeight > target ? "auto" : "hidden";
+    if (wrapper) wrapper.style.height = wrapperHeight;
+  }, [value, floor]);
+
+  const persistFloor = (next: number | null) => {
+    try {
+      if (next === null) {
+        globalThis.localStorage?.removeItem(storageKey);
+      } else {
+        globalThis.localStorage?.setItem(storageKey, String(next));
+      }
+    } catch {
+      // Persistence is best-effort.
+    }
+  };
+
+  const clampFloor = (raw: number): number =>
+    Math.min(Math.max(raw, LINE_PX), maxHeightPx());
+
+  const handlePointerDown = (event: React.PointerEvent<HTMLDivElement>) => {
+    event.preventDefault();
+    event.currentTarget.setPointerCapture(event.pointerId);
+    dragStart.current = {
+      y: event.clientY,
+      floor: floor ?? textareaRef.current?.offsetHeight ?? LINE_PX,
+    };
+    setDragging(true);
+  };
+
+  const handlePointerMove = (event: React.PointerEvent<HTMLDivElement>) => {
+    const start = dragStart.current;
+    if (!dragging || !start) return;
+    // The composer sits at the bottom, so dragging up (smaller Y) grows it.
+    setFloor(clampFloor(start.floor + (start.y - event.clientY)));
+  };
+
+  const handlePointerUp = (event: React.PointerEvent<HTMLDivElement>) => {
+    if (!dragging) return;
+    event.currentTarget.releasePointerCapture(event.pointerId);
+    setDragging(false);
+    dragStart.current = null;
+    setFloor((current) => {
+      persistFloor(current);
+      return current;
+    });
+  };
+
+  const handleKeyDown = (event: React.KeyboardEvent<HTMLDivElement>) => {
+    if (event.key !== "ArrowUp" && event.key !== "ArrowDown") return;
+    event.preventDefault();
+    const delta = event.key === "ArrowUp" ? LINE_PX : -LINE_PX;
+    setFloor((current) => {
+      const base = current ?? textareaRef.current?.offsetHeight ?? LINE_PX;
+      const next = clampFloor(base + delta);
+      persistFloor(next);
+      return next;
+    });
+  };
+
+  return {
+    textareaRef,
+    dragging,
+    resizeHandleProps: {
+      "aria-valuenow": Math.round(floor ?? LINE_PX),
+      onPointerDown: handlePointerDown,
+      onPointerMove: handlePointerMove,
+      onPointerUp: handlePointerUp,
+      onKeyDown: handleKeyDown,
+    },
+  };
+}
diff --git a/desktop/src/features/dev-mode/lib/useDevComposerModes.ts b/desktop/src/features/dev-mode/lib/useDevComposerModes.ts
new file mode 100644
index 0000000000..b2975379b9
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useDevComposerModes.ts
@@ -0,0 +1,91 @@
+import * as React from "react";
+
+import {
+  getSharedChannelIds,
+  relayAgentIsSharedWithUser,
+} from "@/features/agents/lib/agentAutocompleteEligibility";
+import {
+  useManagedAgentsQuery,
+  useRelayAgentsQuery,
+} from "@/features/agents/hooks";
+import { useChannelsQuery } from "@/features/channels/hooks";
+import { useIdentityQuery } from "@/shared/api/hooks";
+import type { ManagedAgent } from "@/shared/api/types";
+import { normalizePubkey } from "@/shared/lib/pubkey";
+
+export type DevAgentTarget = {
+  pubkey: string;
+  name: string;
+  source: "managed" | "relay";
+  /** Present for managed agents; needed to attach + start them. */
+  managedAgent?: ManagedAgent;
+};
+
+/**
+ * The composer target the user cycles through with Tab: plain human chat, or
+ * one of the agents that can be tagged into a new session channel.
+ */
+export type DevComposerMode =
+  | { kind: "chat" }
+  | { kind: "agent"; target: DevAgentTarget };
+
+export function devComposerModeLabel(mode: DevComposerMode): string {
+  return mode.kind === "chat" ? "chat" : mode.target.name;
+}
+
+/**
+ * Global (channel-independent) list of composer modes. Managed agents are
+ * always available — attaching one to a fresh channel is part of the send
+ * flow. Relay agents qualify under the same rules as mention autocomplete,
+ * minus the channel-membership requirement.
+ */
+export function useDevComposerModes(): DevComposerMode[] {
+  const identityQuery = useIdentityQuery();
+  const channelsQuery = useChannelsQuery();
+  const managedAgentsQuery = useManagedAgentsQuery();
+  const relayAgentsQuery = useRelayAgentsQuery();
+
+  const currentPubkey = identityQuery.data?.pubkey ?? null;
+  const channels = channelsQuery.data;
+  const managedAgents = managedAgentsQuery.data;
+  const relayAgents = relayAgentsQuery.data;
+
+  return React.useMemo(() => {
+    const targets = new Map<string, DevAgentTarget>();
+
+    for (const agent of managedAgents ?? []) {
+      const pubkey = normalizePubkey(agent.pubkey);
+      targets.set(pubkey, {
+        pubkey: agent.pubkey,
+        name: agent.name,
+        source: "managed",
+        managedAgent: agent,
+      });
+    }
+
+    const sharedChannelIds = getSharedChannelIds(channels);
+    for (const agent of relayAgents ?? []) {
+      const pubkey = normalizePubkey(agent.pubkey);
+      if (targets.has(pubkey)) continue;
+      if (!relayAgentIsSharedWithUser(agent, sharedChannelIds, currentPubkey)) {
+        continue;
+      }
+      targets.set(pubkey, {
+        pubkey: agent.pubkey,
+        name: agent.name,
+        source: "relay",
+      });
+    }
+
+    const agentModes = [...targets.values()]
+      .sort((left, right) => left.name.localeCompare(right.name))
+      .map(
+        (target): DevComposerMode => ({
+          kind: "agent",
+          target,
+        }),
+      );
+
+    return [{ kind: "chat" } satisfies DevComposerMode, ...agentModes];
+  }, [channels, currentPubkey, managedAgents, relayAgents]);
+}
diff --git a/desktop/src/features/dev-mode/lib/useDevModeShortcuts.ts b/desktop/src/features/dev-mode/lib/useDevModeShortcuts.ts
new file mode 100644
index 0000000000..b2a58952fc
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useDevModeShortcuts.ts
@@ -0,0 +1,100 @@
+import * as React from "react";
+
+import type { Channel } from "@/shared/api/types";
+
+/**
+ * Window-level developer mode shortcuts:
+ *
+ * - ⌘K toggles the command palette
+ * - ⌘N jumps to the fresh composer (new channel)
+ * - ⌘T drafts a side chat in the open channel
+ * - ⌘⇧T drafts a new tab (sub-channel) of the open main
+ * - ⌘[/⌘] cycle through the open channel's tabs, wrapping at the ends
+ */
+export function useDevModeShortcuts({
+  view,
+  activeChannel,
+  activeMainChannel,
+  activeSubChannels,
+  onTogglePalette,
+  onNewSession,
+  onDraftSideChat,
+  onDraftTab,
+  onOpenChannel,
+}: {
+  view: "fresh" | "navigator" | "channel";
+  activeChannel: Channel | null;
+  activeMainChannel: Channel | null;
+  activeSubChannels: Channel[];
+  onTogglePalette: () => void;
+  onNewSession: () => void;
+  /** Null when the current view has no open channel to side-chat in. */
+  onDraftSideChat: (() => void) | null;
+  /** Null when the current view has no main channel to spawn a tab of. */
+  onDraftTab: (() => void) | null;
+  onOpenChannel: (channelId: string) => void;
+}) {
+  React.useEffect(() => {
+    // ⌘K must beat the standard UI's global ⌘K search binding (a window
+    // bubble listener that yields when `event.defaultPrevented`), so the
+    // palette toggle listens in the capture phase.
+    const handlePaletteKeyDown = (event: KeyboardEvent) => {
+      if (
+        event.metaKey &&
+        !event.ctrlKey &&
+        !event.altKey &&
+        !event.shiftKey &&
+        event.key.toLowerCase() === "k"
+      ) {
+        event.preventDefault();
+        onTogglePalette();
+      }
+    };
+    const handleWindowKeyDown = (event: KeyboardEvent) => {
+      if (!event.metaKey || event.ctrlKey || event.altKey) return;
+      const key = event.key.toLowerCase();
+      if (event.shiftKey) {
+        if (key === "t" && onDraftTab) {
+          event.preventDefault();
+          onDraftTab();
+        }
+        return;
+      }
+      if (key === "n") {
+        event.preventDefault();
+        onNewSession();
+      } else if (key === "t" && onDraftSideChat) {
+        event.preventDefault();
+        onDraftSideChat();
+      } else if (
+        (event.key === "[" || event.key === "]") &&
+        view === "channel" &&
+        activeChannel &&
+        activeMainChannel
+      ) {
+        event.preventDefault();
+        const tabs = [activeMainChannel, ...activeSubChannels];
+        if (tabs.length < 2) return;
+        const index = tabs.findIndex((tab) => tab.id === activeChannel.id);
+        const direction = event.key === "]" ? 1 : -1;
+        onOpenChannel(tabs[(index + direction + tabs.length) % tabs.length].id);
+      }
+    };
+    window.addEventListener("keydown", handlePaletteKeyDown, true);
+    window.addEventListener("keydown", handleWindowKeyDown);
+    return () => {
+      window.removeEventListener("keydown", handlePaletteKeyDown, true);
+      window.removeEventListener("keydown", handleWindowKeyDown);
+    };
+  }, [
+    activeChannel,
+    activeMainChannel,
+    activeSubChannels,
+    onDraftSideChat,
+    onDraftTab,
+    onNewSession,
+    onOpenChannel,
+    onTogglePalette,
+    view,
+  ]);
+}
diff --git a/desktop/src/features/dev-mode/lib/useDevSessionActions.ts b/desktop/src/features/dev-mode/lib/useDevSessionActions.ts
new file mode 100644
index 0000000000..2be293028e
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useDevSessionActions.ts
@@ -0,0 +1,395 @@
+import * as React from "react";
+import { useQueryClient } from "@tanstack/react-query";
+
+import { attachManagedAgentToChannel } from "@/features/agents/channelAgents";
+import { useManagedAgentsQuery } from "@/features/agents/hooks";
+import {
+  channelsQueryKey,
+  useCreateChannelMutation,
+} from "@/features/channels/hooks";
+import { useSendMessageMutation } from "@/features/messages/hooks";
+import {
+  buildOutgoingMessage,
+  type ImetaMedia,
+} from "@/features/messages/lib/imetaMediaMarkdown";
+import { addChannelMembers, getCanvas, setCanvas } from "@/shared/api/tauri";
+import { updateChannel } from "@/shared/api/tauriChannels";
+import type { Channel, Identity } from "@/shared/api/types";
+import { normalizePubkey } from "@/shared/lib/pubkey";
+import { generateChannelTitle } from "@/features/dev-mode/lib/channelNaming";
+import type { MentionRecord } from "@/features/dev-mode/lib/mentionRecords";
+import { uniqueChannelName } from "@/features/dev-mode/lib/sessionNaming";
+import {
+  appendSubChannelToParentCanvas,
+  parseSubChannelName,
+  subChannelAnnouncement,
+  subChannelCanvasDoc,
+  subChannelName,
+} from "@/features/dev-mode/lib/subChannels";
+import type {
+  DevAgentTarget,
+  DevComposerMode,
+} from "@/features/dev-mode/lib/useDevComposerModes";
+
+/**
+ * Everyone in the channel sees which agent a prompt is directed at: the
+ * message text carries a `@Name` prefix (matching the standard composer's
+ * mention-text convention) unless the user already typed one. Dev mode lifts
+ * the prefix out of the body at render time and shows it as a "to Name" line
+ * under the author; the standard UI still shows the literal mention text.
+ */
+export function withAgentMention(prompt: string, name: string): string {
+  const escaped = name.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+  const alreadyMentioned = new RegExp(
+    `(^|\\s)@${escaped}(?=$|[\\s,.;:!?)\\]])`,
+    "i",
+  ).test(prompt);
+  return alreadyMentioned ? prompt : `@${name} ${prompt}`;
+}
+
+async function ensureAgentInChannel(channelId: string, target: DevAgentTarget) {
+  if (target.source === "managed" && target.managedAgent) {
+    await attachManagedAgentToChannel(channelId, {
+      agent: target.managedAgent,
+    });
+    return;
+  }
+
+  const result = await addChannelMembers({
+    channelId,
+    pubkeys: [target.pubkey],
+    role: "bot",
+  });
+  const failure = result.errors.find(
+    (error) => normalizePubkey(error.pubkey) === normalizePubkey(target.pubkey),
+  );
+  // "Already a member" satisfies the goal — the membership snapshot this
+  // check ran against can be stale right after a prior send added the agent.
+  if (failure && !/already a member/i.test(failure.error)) {
+    throw new Error(failure.error);
+  }
+}
+
+export function useDevSessionActions(identity: Identity | undefined) {
+  const queryClient = useQueryClient();
+  const createChannelMutation = useCreateChannelMutation();
+  const sendMessageMutation = useSendMessageMutation(null, identity);
+  const managedAgentsQuery = useManagedAgentsQuery();
+  const managedAgents = managedAgentsQuery.data;
+
+  /**
+   * The managed agent whose harness runs the one-shot naming completion:
+   * the agent tagged in the composer when it is a managed one, otherwise any
+   * configured managed agent. Relay agents and plain chat can't run local
+   * completions, so they borrow the first managed agent's harness.
+   */
+  const namingAgentPubkey = React.useCallback(
+    (mode: DevComposerMode | undefined): string | null => {
+      if (mode?.kind === "agent" && mode.target.source === "managed") {
+        return mode.target.pubkey;
+      }
+      return managedAgents?.[0]?.pubkey ?? null;
+    },
+    [managedAgents],
+  );
+
+  /**
+   * Create the channel for a new session, named and described from the
+   * prompt. Creation is separate from the first send so a failure after this
+   * point leaves an open, recoverable session instead of a duplicate channel
+   * on retry.
+   */
+  const createSessionChannel = React.useCallback(
+    async (prompt: string, mode?: DevComposerMode): Promise<Channel> => {
+      const existingNames = new Set(
+        (queryClient.getQueryData<Channel[]>(channelsQueryKey) ?? []).map(
+          (channel) => channel.name,
+        ),
+      );
+
+      // Neutral placeholder, never a prompt slug: the name is replaced by an
+      // agent-generated title, and a lingering "new-session" makes a naming
+      // failure visible instead of masquerading as a generated title.
+      const channel = await createChannelMutation.mutateAsync({
+        name: uniqueChannelName("new-session", existingNames),
+        channelType: "stream",
+        visibility: "open",
+        description: prompt.length > 140 ? `${prompt.slice(0, 139)}…` : prompt,
+      });
+
+      // LLM naming is best-effort and never blocks the session: the channel
+      // opens under its placeholder name and is renamed when a title arrives.
+      void (async () => {
+        const title = await generateChannelTitle(
+          prompt,
+          namingAgentPubkey(mode),
+        );
+        if (!title) {
+          console.warn(
+            `dev-mode: channel naming failed for ${channel.id}; keeping placeholder`,
+          );
+          return;
+        }
+        if (title === channel.name) return;
+        const currentNames = new Set(
+          (queryClient.getQueryData<Channel[]>(channelsQueryKey) ?? [])
+            .filter((candidate) => candidate.id !== channel.id)
+            .map((candidate) => candidate.name),
+        );
+        try {
+          await updateChannel({
+            channelId: channel.id,
+            name: uniqueChannelName(title, currentNames),
+          });
+          await queryClient.invalidateQueries({ queryKey: channelsQueryKey });
+        } catch (error) {
+          // Rename failing leaves the placeholder name, which is still valid.
+          console.warn(
+            `dev-mode: channel rename failed for ${channel.id}`,
+            error,
+          );
+        }
+      })();
+
+      return channel;
+    },
+    [createChannelMutation, namingAgentPubkey, queryClient],
+  );
+
+  const cachedChannels = React.useCallback(
+    () => queryClient.getQueryData<Channel[]>(channelsQueryKey) ?? [],
+    [queryClient],
+  );
+
+  /** The parent channel when `channel` is a `parent--sub`, else null. */
+  const findParentChannel = React.useCallback(
+    (channel: Channel): Channel | null => {
+      const parsed = parseSubChannelName(channel.name);
+      if (!parsed) return null;
+      return (
+        cachedChannels().find(
+          (candidate) =>
+            candidate.name === parsed.parentName && candidate.id !== channel.id,
+        ) ?? null
+      );
+    },
+    [cachedChannels],
+  );
+
+  /**
+   * Spawn a sub-channel of `parent` for a task (mirrors `buzz channels
+   * create --parent`): the child inherits the parent's type/visibility and
+   * is named `parent--<slug>`. The channel opens immediately under a
+   * placeholder slug; naming, the parent announcement, and the
+   * relationship canvases follow best-effort in the background —
+   * announcement and canvases wait for the rename so they reference the
+   * final name.
+   */
+  const createSubChannel = React.useCallback(
+    async (
+      parent: Channel,
+      prompt: string,
+      mode?: DevComposerMode,
+    ): Promise<Channel> => {
+      const existingNames = new Set(
+        cachedChannels().map((channel) => channel.name),
+      );
+      const channel = await createChannelMutation.mutateAsync({
+        name: uniqueChannelName(
+          subChannelName(parent.name, "new-sub"),
+          existingNames,
+        ),
+        // Inherit the parent's type/visibility; DMs can't have subs, so
+        // anything non-forum becomes a stream (dev sessions are streams).
+        channelType: parent.channelType === "forum" ? "forum" : "stream",
+        visibility: parent.visibility,
+        description: prompt.length > 140 ? `${prompt.slice(0, 139)}…` : prompt,
+      });
+
+      void (async () => {
+        let finalName = channel.name;
+        const title = await generateChannelTitle(
+          prompt,
+          namingAgentPubkey(mode),
+        );
+        if (title) {
+          const currentNames = new Set(
+            cachedChannels()
+              .filter((candidate) => candidate.id !== channel.id)
+              .map((candidate) => candidate.name),
+          );
+          const candidate = uniqueChannelName(
+            subChannelName(parent.name, title),
+            currentNames,
+          );
+          try {
+            await updateChannel({ channelId: channel.id, name: candidate });
+            finalName = candidate;
+            await queryClient.invalidateQueries({ queryKey: channelsQueryKey });
+          } catch (error) {
+            console.warn(
+              `dev-mode: sub-channel rename failed for ${channel.id}`,
+              error,
+            );
+          }
+        }
+
+        try {
+          const announcement = await sendMessageMutation.mutateAsync({
+            targetChannel: parent,
+            content: subChannelAnnouncement(finalName),
+          });
+          await setCanvas({
+            channelId: channel.id,
+            content: subChannelCanvasDoc({
+              parentName: parent.name,
+              parentId: parent.id,
+              announcementEventId: announcement.id,
+              task: prompt,
+            }),
+          });
+          const parentCanvas = await getCanvas(parent.id);
+          await setCanvas({
+            channelId: parent.id,
+            content: appendSubChannelToParentCanvas(
+              parentCanvas.content,
+              finalName,
+              prompt,
+            ),
+          });
+        } catch (error) {
+          console.warn(
+            `dev-mode: sub-channel announcement/canvas setup failed for ${channel.id}`,
+            error,
+          );
+        }
+      })();
+
+      return channel;
+    },
+    [
+      cachedChannels,
+      createChannelMutation,
+      namingAgentPubkey,
+      queryClient,
+      sendMessageMutation,
+    ],
+  );
+
+  /**
+   * Send a prompt into a session, optionally as a reply inside an existing
+   * thread (`parentEventId`). In an agent mode, the agent is attached first
+   * when it is not yet a member (membership must land before the mention or
+   * the harness filter drops it) — agents are not limited to a single
+   * channel.
+   */
+  const sendToSession = React.useCallback(
+    async (
+      channel: Channel,
+      prompt: string,
+      mode: DevComposerMode,
+      parentEventId?: string,
+      mentions: MentionRecord[] = [],
+      media: ImetaMedia[] = [],
+    ) => {
+      // Sub-channel invariant (client-side; the relay knows nothing about
+      // sub-channels): everyone in `parent--sub` must belong to `parent`.
+      const parentChannel = findParentChannel(channel);
+      const parentMemberPubkeys = parentChannel
+        ? new Set(
+            parentChannel.memberPubkeys.map((pubkey) =>
+              normalizePubkey(pubkey),
+            ),
+          )
+        : null;
+
+      if (mode.kind === "agent") {
+        const agentPubkey = normalizePubkey(mode.target.pubkey);
+        if (parentChannel && !parentMemberPubkeys?.has(agentPubkey)) {
+          await ensureAgentInChannel(parentChannel.id, mode.target);
+          parentMemberPubkeys?.add(agentPubkey);
+        }
+        const isMember = channel.memberPubkeys.some(
+          (pubkey) => normalizePubkey(pubkey) === agentPubkey,
+        );
+        if (!isMember) {
+          await ensureAgentInChannel(channel.id, mode.target);
+        }
+      }
+
+      // Tagging someone pulls them into the channel (mirroring how the
+      // targeted agent is auto-attached); best-effort so a failed add never
+      // blocks the send — the p tag still goes out.
+      const memberPubkeys = new Set(
+        channel.memberPubkeys.map((pubkey) => normalizePubkey(pubkey)),
+      );
+      if (mode.kind === "agent") {
+        memberPubkeys.add(normalizePubkey(mode.target.pubkey));
+      }
+      let nonMembers = mentions.filter(
+        (mention) => !memberPubkeys.has(normalizePubkey(mention.pubkey)),
+      );
+      if (parentMemberPubkeys) {
+        const outsiders = nonMembers.filter(
+          (mention) =>
+            !parentMemberPubkeys.has(normalizePubkey(mention.pubkey)),
+        );
+        if (outsiders.length > 0) {
+          console.warn(
+            `dev-mode: skipping auto-add of ${outsiders.length} mention(s) not in the parent channel of ${channel.name}`,
+          );
+          nonMembers = nonMembers.filter((mention) =>
+            parentMemberPubkeys.has(normalizePubkey(mention.pubkey)),
+          );
+        }
+      }
+      for (const role of ["member", "bot"] as const) {
+        const pubkeys = nonMembers
+          .filter((mention) => (role === "bot") === mention.isAgent)
+          .map((mention) => mention.pubkey);
+        if (pubkeys.length === 0) continue;
+        try {
+          await addChannelMembers({ channelId: channel.id, pubkeys, role });
+        } catch (addError) {
+          console.warn(
+            `dev-mode: failed to add mentioned ${role}s to ${channel.id}:`,
+            addError,
+          );
+        }
+      }
+
+      const mentionPubkeys = [
+        ...new Set([
+          ...(mode.kind === "agent" ? [mode.target.pubkey] : []),
+          ...mentions.map((mention) => mention.pubkey),
+        ]),
+      ];
+
+      // Attachments append `![image|video](url)` lines to the body (the
+      // renderer keys on URLs literally present in the content) and ride as
+      // NIP-92 imeta tags — the same wire shape the standard composer sends.
+      const { content, mediaTags } = buildOutgoingMessage(
+        mode.kind === "agent"
+          ? withAgentMention(prompt, mode.target.name)
+          : prompt,
+        media,
+      );
+
+      return await sendMessageMutation.mutateAsync({
+        targetChannel: channel,
+        content,
+        mentionPubkeys: mentionPubkeys.length > 0 ? mentionPubkeys : undefined,
+        parentEventId: parentEventId ?? null,
+        mediaTags,
+      });
+    },
+    [findParentChannel, sendMessageMutation],
+  );
+
+  return {
+    createSessionChannel,
+    createSubChannel,
+    sendToSession,
+    isCreatingChannel: createChannelMutation.isPending,
+  };
+}
diff --git a/desktop/src/features/dev-mode/lib/useMemberNameResolver.ts b/desktop/src/features/dev-mode/lib/useMemberNameResolver.ts
new file mode 100644
index 0000000000..effb0c37cf
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useMemberNameResolver.ts
@@ -0,0 +1,55 @@
+import * as React from "react";
+
+import { useChannelMembersQuery } from "@/features/channels/hooks";
+import { useUsersBatchQuery } from "@/features/profile/hooks";
+import { truncatePubkey } from "@/shared/lib/pubkey";
+
+export type NameResolver = (pubkey: string) => string;
+
+export type AgentResolver = (pubkey: string) => boolean;
+
+/** Whether a pubkey belongs to an agent member of the channel. */
+export function useMemberAgentResolver(channelId: string): AgentResolver {
+  const membersQuery = useChannelMembersQuery(channelId);
+  return React.useCallback<AgentResolver>(
+    (pubkey) =>
+      membersQuery.data?.some(
+        (candidate) =>
+          candidate.pubkey === pubkey &&
+          (candidate.isAgent || candidate.role === "bot"),
+      ) ?? false,
+    [membersQuery.data],
+  );
+}
+
+/**
+ * Resolves names from the channel's member list, with a batch profile
+ * lookup as fallback for `extraPubkeys` that are no longer members —
+ * membership rows name people who already left the channel.
+ */
+export function useMemberNameResolver(
+  channelId: string,
+  extraPubkeys: readonly string[] = [],
+): NameResolver {
+  const membersQuery = useChannelMembersQuery(channelId);
+  const members = membersQuery.data;
+
+  const unknownPubkeys = React.useMemo(
+    () =>
+      extraPubkeys.filter(
+        (pubkey) => !members?.some((candidate) => candidate.pubkey === pubkey),
+      ),
+    [extraPubkeys, members],
+  );
+  const profilesQuery = useUsersBatchQuery(unknownPubkeys);
+
+  return React.useCallback<NameResolver>(
+    (pubkey) => {
+      const member = members?.find((candidate) => candidate.pubkey === pubkey);
+      if (member?.displayName) return member.displayName;
+      const profile = profilesQuery.data?.profiles[pubkey.toLowerCase()];
+      return profile?.displayName || profile?.name || truncatePubkey(pubkey);
+    },
+    [members, profilesQuery.data],
+  );
+}
diff --git a/desktop/src/features/dev-mode/lib/useMentionAutocomplete.ts b/desktop/src/features/dev-mode/lib/useMentionAutocomplete.ts
new file mode 100644
index 0000000000..246e902e13
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useMentionAutocomplete.ts
@@ -0,0 +1,245 @@
+import * as React from "react";
+
+import { useChannelMembersQuery } from "@/features/channels/hooks";
+import {
+  extractMentions,
+  type MentionRecord,
+} from "@/features/dev-mode/lib/mentionRecords";
+import { useUserSearchQuery } from "@/features/profile/hooks";
+import { detectPrefixQuery } from "@/shared/lib/detectPrefixQuery";
+import { normalizePubkey } from "@/shared/lib/pubkey";
+
+const MAX_SUGGESTIONS = 6;
+
+export type MentionSuggestion = MentionRecord & {
+  isMember: boolean;
+};
+
+/**
+ * `@user` autocomplete for a dev-mode composer textarea, mirroring the
+ * `#channel` autocomplete's keyboard contract: typing `@` plus a prefix at
+ * the caret opens suggestions; ↑/↓ move, Tab/Enter accept (inserting
+ * `@Display Name `), Escape dismisses. Channel members rank first, then
+ * relay-wide `search_users` results. `extract` maps `@Name`s still present
+ * in the text back to pubkeys at send time.
+ */
+export function useMentionAutocomplete({
+  channelId,
+  selfPubkey,
+  value,
+  onChange,
+  textareaRef,
+}: {
+  channelId: string | null;
+  selfPubkey: string | null;
+  value: string;
+  onChange: (value: string) => void;
+  textareaRef: React.RefObject<HTMLTextAreaElement | null>;
+}) {
+  const membersQuery = useChannelMembersQuery(channelId);
+  const [cursor, setCursor] = React.useState(0);
+  const [selectedIndex, setSelectedIndex] = React.useState(0);
+  const [dismissed, setDismissed] = React.useState(false);
+
+  const memberSuggestions = React.useMemo<MentionSuggestion[]>(
+    () =>
+      (membersQuery.data ?? []).flatMap((member) =>
+        member.displayName
+          ? [
+              {
+                pubkey: member.pubkey,
+                name: member.displayName,
+                isAgent: member.isAgent || member.role === "bot",
+                isMember: true,
+              },
+            ]
+          : [],
+      ),
+    [membersQuery.data],
+  );
+
+  // Every relay user seen this composer session, so multi-word names keep
+  // the query open across spaces (and suggestions survive the moment a new
+  // search key is still loading).
+  const [seenRelayUsers, setSeenRelayUsers] = React.useState<
+    ReadonlyMap<string, MentionSuggestion>
+  >(new Map());
+
+  const knownNamesLower = React.useMemo(
+    () => [
+      ...memberSuggestions.map((suggestion) => suggestion.name.toLowerCase()),
+      ...[...seenRelayUsers.values()].map((suggestion) =>
+        suggestion.name.toLowerCase(),
+      ),
+    ],
+    [memberSuggestions, seenRelayUsers],
+  );
+
+  const detection = React.useMemo(
+    () => detectPrefixQuery("@", value, cursor, knownNamesLower),
+    [cursor, knownNamesLower, value],
+  );
+
+  const searchQuery = useUserSearchQuery(detection?.query ?? "", {
+    enabled: detection !== null,
+    limit: 8,
+  });
+
+  const searchResults = searchQuery.data;
+  React.useEffect(() => {
+    if (!searchResults?.length) return;
+    setSeenRelayUsers((current) => {
+      let next: Map<string, MentionSuggestion> | null = null;
+      for (const user of searchResults) {
+        const name = user.displayName?.trim();
+        if (!name) continue;
+        const key = normalizePubkey(user.pubkey);
+        if (current.has(key)) continue;
+        if (!next) next = new Map(current);
+        next.set(key, {
+          pubkey: user.pubkey,
+          name,
+          isAgent: user.isAgent,
+          isMember: false,
+        });
+      }
+      return next ?? current;
+    });
+  }, [searchResults]);
+
+  const suggestions = React.useMemo<MentionSuggestion[]>(() => {
+    if (!detection) return [];
+    const candidates: MentionSuggestion[] = [
+      ...memberSuggestions,
+      ...(searchResults ?? []).flatMap((user) => {
+        const name = user.displayName?.trim();
+        return name
+          ? [
+              {
+                pubkey: user.pubkey,
+                name,
+                isAgent: user.isAgent,
+                isMember: false,
+              },
+            ]
+          : [];
+      }),
+      ...seenRelayUsers.values(),
+    ];
+    const needle = detection.query.toLowerCase();
+    const seen = new Set<string>();
+    const starts: MentionSuggestion[] = [];
+    const contains: MentionSuggestion[] = [];
+    for (const candidate of candidates) {
+      const key = normalizePubkey(candidate.pubkey);
+      if (seen.has(key)) continue;
+      if (selfPubkey && key === normalizePubkey(selfPubkey)) continue;
+      const name = candidate.name.toLowerCase();
+      if (name.startsWith(needle)) {
+        starts.push(candidate);
+      } else if (name.includes(needle)) {
+        contains.push(candidate);
+      } else {
+        continue;
+      }
+      seen.add(key);
+    }
+    return [...starts, ...contains].slice(0, MAX_SUGGESTIONS);
+  }, [detection, memberSuggestions, searchResults, seenRelayUsers, selfPubkey]);
+
+  const open = !dismissed && suggestions.length > 0;
+
+  // A fresh query (typing/caret movement) clears the selection and any
+  // Escape dismissal from the previous query.
+  const queryKey = detection
+    ? `${detection.startIndex}:${detection.query}`
+    : null;
+  const previousQueryKeyRef = React.useRef(queryKey);
+  if (previousQueryKeyRef.current !== queryKey) {
+    previousQueryKeyRef.current = queryKey;
+    if (selectedIndex !== 0) setSelectedIndex(0);
+    if (dismissed) setDismissed(false);
+  }
+
+  const syncCursor = React.useCallback((target: HTMLTextAreaElement) => {
+    setCursor(target.selectionStart ?? target.value.length);
+  }, []);
+
+  // Accepted suggestions, so `extract` can map typed `@Name`s back to
+  // pubkeys — relay users aren't channel members yet.
+  const acceptedRef = React.useRef(new Map<string, MentionRecord>());
+
+  const accept = React.useCallback(
+    (suggestion: MentionSuggestion) => {
+      if (!detection) return;
+      const before = value.slice(0, detection.startIndex);
+      const inserted = `@${suggestion.name} `;
+      const next = before + inserted + value.slice(cursor);
+      onChange(next);
+      acceptedRef.current.set(normalizePubkey(suggestion.pubkey), {
+        name: suggestion.name,
+        pubkey: suggestion.pubkey,
+        isAgent: suggestion.isAgent,
+      });
+      const caret = before.length + inserted.length;
+      setCursor(caret);
+      requestAnimationFrame(() => {
+        const textarea = textareaRef.current;
+        // Skip if the user already typed past the accept — repositioning
+        // now would drop their keystrokes into the middle of the text.
+        if (!textarea || textarea.value !== next) return;
+        textarea.setSelectionRange(caret, caret);
+      });
+    },
+    [cursor, detection, onChange, textareaRef, value],
+  );
+
+  const handleKeyDown = React.useCallback(
+    (event: React.KeyboardEvent<HTMLTextAreaElement>): boolean => {
+      if (!open) return false;
+      // Modified keys belong to composer shortcuts (e.g. ⌥↑ channel step).
+      if (event.altKey || event.metaKey || event.ctrlKey) return false;
+      if (event.key === "ArrowUp" || event.key === "ArrowDown") {
+        event.preventDefault();
+        const delta = event.key === "ArrowUp" ? -1 : 1;
+        setSelectedIndex(
+          (current) =>
+            (current + delta + suggestions.length) % suggestions.length,
+        );
+        return true;
+      }
+      if (event.key === "Tab" || event.key === "Enter") {
+        event.preventDefault();
+        accept(suggestions[selectedIndex] ?? suggestions[0]);
+        return true;
+      }
+      if (event.key === "Escape") {
+        event.preventDefault();
+        setDismissed(true);
+        return true;
+      }
+      return false;
+    },
+    [accept, open, selectedIndex, suggestions],
+  );
+
+  /** Mentions still present in the text: accepted users + channel members. */
+  const extract = React.useCallback(
+    (text: string): MentionRecord[] =>
+      extractMentions(text, [
+        ...acceptedRef.current.values(),
+        ...memberSuggestions,
+      ]),
+    [memberSuggestions],
+  );
+
+  return {
+    open,
+    suggestions,
+    selectedIndex,
+    accept,
+    handleKeyDown,
+    syncCursor,
+    extract,
+  };
+}
diff --git a/desktop/src/features/dev-mode/lib/useNavigatorWidth.ts b/desktop/src/features/dev-mode/lib/useNavigatorWidth.ts
new file mode 100644
index 0000000000..df68e2529d
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useNavigatorWidth.ts
@@ -0,0 +1,90 @@
+import * as React from "react";
+
+const STORAGE_KEY = "buzz.devMode.channelNavigatorWidth";
+const MIN_PX = 200;
+const MAX_PX = 480;
+const DEFAULT_PX = 288;
+
+function clamp(raw: number): number {
+  return Math.min(MAX_PX, Math.max(MIN_PX, raw));
+}
+
+function readStoredWidth(): number {
+  try {
+    const raw = globalThis.localStorage?.getItem(STORAGE_KEY);
+    const value = raw === null || raw === undefined ? Number.NaN : Number(raw);
+    if (Number.isFinite(value)) {
+      return clamp(value);
+    }
+  } catch {
+    // Fall through to the default width.
+  }
+  return DEFAULT_PX;
+}
+
+function persistWidth(width: number) {
+  try {
+    globalThis.localStorage?.setItem(STORAGE_KEY, String(width));
+  } catch {
+    // Persistence is best-effort.
+  }
+}
+
+export type NavigatorWidthControls = ReturnType<typeof useNavigatorWidth>;
+
+/**
+ * Persisted, pointer-draggable width for the channel navigator (clamped
+ * 200–480px). Spread `dividerProps` on a vertical separator at the
+ * navigator's right edge; Left/Right arrows nudge the width when focused.
+ */
+export function useNavigatorWidth() {
+  const [width, setWidth] = React.useState(readStoredWidth);
+  const [dragging, setDragging] = React.useState(false);
+  const dragStart = React.useRef<{ x: number; width: number } | null>(null);
+
+  const handlePointerDown = (event: React.PointerEvent<HTMLDivElement>) => {
+    event.preventDefault();
+    event.currentTarget.setPointerCapture(event.pointerId);
+    dragStart.current = { x: event.clientX, width };
+    setDragging(true);
+  };
+
+  const handlePointerMove = (event: React.PointerEvent<HTMLDivElement>) => {
+    const start = dragStart.current;
+    if (!dragging || !start) return;
+    setWidth(clamp(start.width + (event.clientX - start.x)));
+  };
+
+  const handlePointerUp = (event: React.PointerEvent<HTMLDivElement>) => {
+    if (!dragging) return;
+    event.currentTarget.releasePointerCapture(event.pointerId);
+    setDragging(false);
+    dragStart.current = null;
+    setWidth((current) => {
+      persistWidth(current);
+      return current;
+    });
+  };
+
+  const handleKeyDown = (event: React.KeyboardEvent<HTMLDivElement>) => {
+    if (event.key !== "ArrowLeft" && event.key !== "ArrowRight") return;
+    event.preventDefault();
+    const delta = event.key === "ArrowLeft" ? -16 : 16;
+    setWidth((current) => {
+      const next = clamp(current + delta);
+      persistWidth(next);
+      return next;
+    });
+  };
+
+  return {
+    width,
+    dragging,
+    dividerProps: {
+      onPointerDown: handlePointerDown,
+      onPointerMove: handlePointerMove,
+      onPointerUp: handlePointerUp,
+      onKeyDown: handleKeyDown,
+    },
+  };
+}
diff --git a/desktop/src/features/dev-mode/lib/usePageTitle.ts b/desktop/src/features/dev-mode/lib/usePageTitle.ts
new file mode 100644
index 0000000000..4ed403d231
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/usePageTitle.ts
@@ -0,0 +1,60 @@
+import * as React from "react";
+
+import { invokeTauri } from "@/shared/api/tauri";
+
+/**
+ * Module-level cache so each URL is fetched once per app session no matter
+ * how many messages mention it (same pattern as `useResolvedLinkPreviews`).
+ */
+const titleCache = new Map<string, Promise<string | null> | string | null>();
+
+function cacheTitle(href: string): Promise<string | null> {
+  const cached = titleCache.get(href);
+  if (cached instanceof Promise) return cached;
+  if (cached !== undefined) return Promise.resolve(cached);
+
+  // Authenticated sources first: Slack permalinks and private Google files
+  // resolve through `sq agent-tools` into labels like "joah in #general" or
+  // the doc's real title. Anything unresolved falls back to the generic
+  // HTML page-title fetch.
+  const promise = invokeTauri<string | null>("fetch_agent_link_label", { href })
+    .catch(() => null)
+    .then(
+      (label) =>
+        label ??
+        invokeTauri<string | null>("fetch_page_title", { href }).catch(
+          () => null,
+        ),
+    )
+    .then((title) => {
+      titleCache.set(href, title);
+      return title;
+    });
+  titleCache.set(href, promise);
+  return promise;
+}
+
+/**
+ * Best-effort page title for a URL, or null while loading / when the page
+ * can't be fetched (auth walls, non-HTML, timeouts). A null href skips the
+ * fetch entirely (the caller already has display text).
+ */
+export function usePageTitle(href: string | null): string | null {
+  const cached = href === null ? undefined : titleCache.get(href);
+  const [title, setTitle] = React.useState<string | null>(
+    typeof cached === "string" ? cached : null,
+  );
+
+  React.useEffect(() => {
+    if (href === null) return;
+    let cancelled = false;
+    void cacheTitle(href).then((resolved) => {
+      if (!cancelled && resolved) setTitle(resolved);
+    });
+    return () => {
+      cancelled = true;
+    };
+  }, [href]);
+
+  return title;
+}
diff --git a/desktop/src/features/dev-mode/lib/usePinnedScroll.ts b/desktop/src/features/dev-mode/lib/usePinnedScroll.ts
new file mode 100644
index 0000000000..239e4f6b16
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/usePinnedScroll.ts
@@ -0,0 +1,48 @@
+import * as React from "react";
+
+/** Distance from the bottom (px) within which the view stays pinned. */
+const PIN_THRESHOLD = 48;
+
+/**
+ * Keep a scroll container pinned to the bottom while its content grows
+ * (live agent output, replies loading in), unless the user scrolled up.
+ * A resetKey change (channel or thread switch) re-pins the view.
+ */
+export function usePinnedScroll(resetKey: string) {
+  const scrollRef = React.useRef<HTMLDivElement>(null);
+  const contentRef = React.useRef<HTMLDivElement>(null);
+  const pinnedRef = React.useRef(true);
+
+  const handleScroll = React.useCallback(() => {
+    const node = scrollRef.current;
+    if (!node) return;
+    pinnedRef.current =
+      node.scrollHeight - node.scrollTop - node.clientHeight < PIN_THRESHOLD;
+  }, []);
+
+  // biome-ignore lint/correctness/useExhaustiveDependencies: intentional — a resetKey change re-pins the view to the bottom
+  React.useLayoutEffect(() => {
+    const node = scrollRef.current;
+    if (!node) return;
+    node.scrollTop = node.scrollHeight;
+    pinnedRef.current = true;
+  }, [resetKey]);
+
+  React.useEffect(() => {
+    const content = contentRef.current;
+    const scroller = scrollRef.current;
+    if (!content || !scroller) return;
+    const observer = new ResizeObserver(() => {
+      if (pinnedRef.current) {
+        scroller.scrollTop = scroller.scrollHeight;
+      }
+    });
+    observer.observe(content);
+    // The scroller itself resizes when the composer grows (newlines, drag)
+    // or the split moves — a pinned view must stay glued to the bottom.
+    observer.observe(scroller);
+    return () => observer.disconnect();
+  }, []);
+
+  return { scrollRef, contentRef, handleScroll };
+}
diff --git a/desktop/src/features/dev-mode/lib/useShellFocusGuards.ts b/desktop/src/features/dev-mode/lib/useShellFocusGuards.ts
new file mode 100644
index 0000000000..74be647b4a
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useShellFocusGuards.ts
@@ -0,0 +1,96 @@
+import * as React from "react";
+
+/**
+ * Keeps the keyboard anchored to a text input across window refocus and
+ * shell clicks:
+ *
+ * - Refocusing the window restores whichever text input last had the
+ *   keyboard (main composer, side-chat composer, palette search), falling
+ *   back to the composer if it unmounted meanwhile.
+ * - Clicks on non-interactive chrome must not blur the active input — this
+ *   also covers the click that refocuses the window landing on dead space.
+ *   Transcript areas opt out (data-allow-text-selection) so message text
+ *   stays drag-selectable; the mouseup handler restores focus afterwards
+ *   when the click ended without selecting text.
+ *
+ * While card selection owns the keyboard, nothing puts the caret back in a
+ * box.
+ */
+export function useShellFocusGuards({
+  cardSelectionActive,
+  focusComposer,
+}: {
+  cardSelectionActive: boolean;
+  focusComposer: () => void;
+}) {
+  const lastFocusedRef = React.useRef<HTMLElement | null>(null);
+
+  const handleFocusCapture = React.useCallback(
+    (event: React.FocusEvent<HTMLDivElement>) => {
+      const target = event.target;
+      if (
+        target instanceof HTMLElement &&
+        target.matches("textarea, input, [contenteditable='true']")
+      ) {
+        lastFocusedRef.current = target;
+      }
+    },
+    [],
+  );
+
+  React.useEffect(() => {
+    const handleWindowFocus = () => {
+      if (cardSelectionActive) return;
+      const last = lastFocusedRef.current;
+      if (last?.isConnected) {
+        last.focus();
+      } else {
+        focusComposer();
+      }
+    };
+    window.addEventListener("focus", handleWindowFocus);
+    return () => window.removeEventListener("focus", handleWindowFocus);
+  }, [cardSelectionActive, focusComposer]);
+
+  const handleShellMouseDown = React.useCallback(
+    (event: React.MouseEvent<HTMLDivElement>) => {
+      const target = event.target;
+      if (
+        target instanceof HTMLElement &&
+        !target.closest(
+          "button, a, input, textarea, select, [role='button'], [role='separator'], [contenteditable='true'], [data-allow-text-selection]",
+        )
+      ) {
+        event.preventDefault();
+      }
+    },
+    [],
+  );
+
+  const handleShellMouseUp = React.useCallback(
+    (event: React.MouseEvent<HTMLDivElement>) => {
+      const target = event.target;
+      if (
+        !(target instanceof HTMLElement) ||
+        !target.closest("[data-allow-text-selection]") ||
+        target.closest("button, a, input, textarea, [contenteditable='true']")
+      ) {
+        return;
+      }
+      if (cardSelectionActive) return;
+      requestAnimationFrame(() => {
+        const selection = window.getSelection();
+        if (selection && !selection.isCollapsed) return;
+        const last = lastFocusedRef.current;
+        if (last?.isConnected) {
+          last.focus();
+        } else {
+          focusComposer();
+        }
+      });
+    },
+    [cardSelectionActive, focusComposer],
+  );
+
+  return { handleFocusCapture, handleShellMouseDown, handleShellMouseUp };
+}
diff --git a/desktop/src/features/dev-mode/lib/useUnreadRouting.ts b/desktop/src/features/dev-mode/lib/useUnreadRouting.ts
new file mode 100644
index 0000000000..3df68f4c7d
--- /dev/null
+++ b/desktop/src/features/dev-mode/lib/useUnreadRouting.ts
@@ -0,0 +1,149 @@
+import * as React from "react";
+
+import { useAppShell } from "@/app/AppShellContext";
+import { useChannelMembersQuery } from "@/features/channels/hooks";
+import type { SubChannelIndex } from "@/features/dev-mode/lib/subChannels";
+import {
+  byCreatedAscending,
+  DEV_MESSAGE_KINDS,
+  selectInlineVisibleCount,
+} from "@/features/dev-mode/lib/transcriptRoots";
+import { findUnreadFamilyTarget } from "@/features/dev-mode/lib/unreadThreads";
+import { useThreadReplies } from "@/features/messages/useThreadReplies";
+import type { Channel, RelayEvent } from "@/shared/api/types";
+
+/**
+ * Opening a channel from its navigator row routes to what needs attention:
+ * the family's unread tab. The unread thread's side chat opens only when
+ * its unread replies are collapsed — hidden behind the "… N more replies"
+ * affordance because a human already responded in the thread. Unread
+ * replies that render inline in the main chat view (the leading agent run)
+ * are marked read just by looking at the channel, so no side chat is
+ * forced open for them.
+ *
+ * The decision needs the thread's subtree and the channel's member roles,
+ * so it is deferred until both load; any navigation elsewhere makes the
+ * deferred decision stale.
+ *
+ * Returns the routed open. Explicit destinations (tab clicks, palette,
+ * ⌘[/⌘], ⌥↑↓) keep using the plain open and land exactly where asked.
+ */
+export function useUnreadRouting({
+  subIndex,
+  unreadChannelIds,
+  topLevelUnreadChannelIds,
+  activeChannel,
+  roots,
+  openChannel,
+  openThread,
+}: {
+  subIndex: SubChannelIndex;
+  unreadChannelIds: ReadonlySet<string>;
+  topLevelUnreadChannelIds: ReadonlySet<string>;
+  /** The channel whose transcript (roots) is currently loaded. */
+  activeChannel: Channel | null;
+  roots: readonly RelayEvent[];
+  openChannel: (channelId: string) => void;
+  /** Select the root's card and open its side chat. */
+  openThread: (rootId: string) => void;
+}): (channelId: string) => void {
+  const { getThreadReadAt, threadActivityItems } = useAppShell();
+  const activeChannelId = activeChannel?.id ?? null;
+
+  const [pending, setPending] = React.useState<{
+    channelId: string;
+    rootId: string;
+  } | null>(null);
+
+  React.useEffect(() => {
+    if (pending && pending.channelId !== activeChannelId) {
+      setPending(null);
+    }
+  }, [activeChannelId, pending]);
+
+  // Shares the transcript's thread-subtree and member query caches, so the
+  // routed channel is fetching these anyway.
+  const pendingChannel =
+    pending && activeChannelId === pending.channelId ? activeChannel : null;
+  const repliesQuery = useThreadReplies(
+    pendingChannel,
+    pending?.rootId ?? null,
+  );
+  const membersQuery = useChannelMembersQuery(pendingChannel?.id ?? null);
+
+  // Complete the routing once the target root, its subtree, and the member
+  // roles are loaded. Declared after the shell's selection-reset effect
+  // runs for the channel switch, so the reset cannot clobber the opened
+  // side chat.
+  React.useEffect(() => {
+    if (!pending || pending.channelId !== activeChannelId) return;
+    if (!roots.some((root) => root.id === pending.rootId)) return;
+    const subtree = repliesQuery.data;
+    const members = membersQuery.data;
+    if (subtree === undefined || members === undefined) return;
+
+    const replies = subtree
+      .filter((event) => DEV_MESSAGE_KINDS.has(event.kind))
+      .sort(byCreatedAscending);
+    const isAgent = (pubkey: string) =>
+      members.some(
+        (member) =>
+          member.pubkey === pubkey && (member.isAgent || member.role === "bot"),
+      );
+    const visibleCount = selectInlineVisibleCount(replies, isAgent);
+    const readAt = getThreadReadAt(pending.rootId, pending.channelId);
+    const hasCollapsedUnread = replies
+      .slice(visibleCount)
+      .some((reply) => readAt === null || reply.created_at > readAt);
+
+    setPending(null);
+    if (hasCollapsedUnread) {
+      openThread(pending.rootId);
+    }
+  }, [
+    activeChannelId,
+    getThreadReadAt,
+    membersQuery.data,
+    openThread,
+    pending,
+    repliesQuery.data,
+    roots,
+  ]);
+
+  return React.useCallback(
+    (channelId: string) => {
+      const mainId = subIndex.parentIdByChildId.get(channelId) ?? channelId;
+      const target = findUnreadFamilyTarget({
+        familyChannelIds: [
+          mainId,
+          ...(subIndex.subsByParentId.get(mainId) ?? []).map((sub) => sub.id),
+        ],
+        unreadChannelIds,
+        topLevelUnreadChannelIds,
+        threadActivity: threadActivityItems,
+        getThreadReadAt,
+      });
+      if (!target) {
+        openChannel(channelId);
+        return;
+      }
+      if (target.channelId !== activeChannelId) {
+        openChannel(target.channelId);
+      }
+      setPending(
+        target.rootId
+          ? { channelId: target.channelId, rootId: target.rootId }
+          : null,
+      );
+    },
+    [
+      activeChannelId,
+      getThreadReadAt,
+      openChannel,
+      subIndex,
+      threadActivityItems,
+      topLevelUnreadChannelIds,
+      unreadChannelIds,
+    ],
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevChannelMembers.tsx b/desktop/src/features/dev-mode/ui/DevChannelMembers.tsx
new file mode 100644
index 0000000000..f307c21fe9
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevChannelMembers.tsx
@@ -0,0 +1,54 @@
+import { useChannelMembersQuery } from "@/features/channels/hooks";
+import { useAuthorColorResolver } from "@/features/dev-mode/lib/authorColors";
+import type { Channel } from "@/shared/api/types";
+import { truncatePubkey } from "@/shared/lib/pubkey";
+
+/**
+ * Above this, the top bar collapses to a member count — channels can have
+ * 1000+ members, and a name list neither fits nor deserves a roster fetch.
+ */
+export const MAX_INLINE_MEMBERS = 4;
+
+/** Top-bar member summary; click opens the palette's member browser. */
+export function DevChannelMembers({
+  channel,
+  onShowMembers,
+}: {
+  channel: Channel;
+  onShowMembers: () => void;
+}) {
+  const showNames =
+    channel.memberCount > 0 && channel.memberCount <= MAX_INLINE_MEMBERS;
+  const membersQuery = useChannelMembersQuery(channel.id, showNames);
+  const resolveColor = useAuthorColorResolver();
+
+  if (channel.memberCount === 0) return null;
+
+  const members = showNames ? (membersQuery.data ?? []) : [];
+
+  return (
+    <button
+      className="pointer-events-auto flex min-w-0 cursor-pointer items-baseline gap-1.5 truncate text-muted-foreground/70 hover:text-muted-foreground"
+      data-testid="dev-mode-channel-members"
+      onClick={onShowMembers}
+      title="View members"
+      type="button"
+    >
+      {showNames && members.length > 0 ? (
+        members.map((member) => (
+          <span
+            key={member.pubkey}
+            style={{ color: resolveColor(member.pubkey) }}
+          >
+            {member.displayName || truncatePubkey(member.pubkey)}
+          </span>
+        ))
+      ) : (
+        <span>
+          {channel.memberCount}{" "}
+          {channel.memberCount === 1 ? "member" : "members"}
+        </span>
+      )}
+    </button>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevChannelNavigator.tsx b/desktop/src/features/dev-mode/ui/DevChannelNavigator.tsx
new file mode 100644
index 0000000000..df61e29a80
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevChannelNavigator.tsx
@@ -0,0 +1,184 @@
+import * as React from "react";
+
+import {
+  type ChannelGroup,
+  toggleChannelPinned,
+} from "@/features/dev-mode/lib/pinnedChannels";
+import type { NavigatorWidthControls } from "@/features/dev-mode/lib/useNavigatorWidth";
+import type { Channel } from "@/shared/api/types";
+import { cn } from "@/shared/lib/cn";
+
+function formatRelativeTime(iso: string | null) {
+  if (!iso) return "";
+  const deltaSeconds = Math.max(
+    0,
+    Math.floor((Date.now() - new Date(iso).getTime()) / 1_000),
+  );
+  if (deltaSeconds < 60) return "now";
+  if (deltaSeconds < 3_600) return `${Math.floor(deltaSeconds / 60)}m`;
+  if (deltaSeconds < 86_400) return `${Math.floor(deltaSeconds / 3_600)}h`;
+  return `${Math.floor(deltaSeconds / 86_400)}d`;
+}
+
+function ChannelRow({
+  channel,
+  isHighlighted,
+  isPinned,
+  isUnread,
+  onOpen,
+}: {
+  channel: Channel;
+  isHighlighted: boolean;
+  isPinned: boolean;
+  isUnread: boolean;
+  onOpen: (channelId: string) => void;
+}) {
+  const scrollHighlightedIntoView = React.useCallback(
+    (node: HTMLDivElement | null) => {
+      node?.scrollIntoView({ block: "nearest" });
+    },
+    [],
+  );
+
+  return (
+    <div
+      ref={isHighlighted ? scrollHighlightedIntoView : undefined}
+      className={cn(
+        "group relative flex items-baseline",
+        isHighlighted
+          ? "bg-primary/15 text-foreground"
+          : isUnread
+            ? "text-foreground hover:bg-muted/40"
+            : "text-muted-foreground hover:bg-muted/40 hover:text-foreground",
+      )}
+    >
+      <button
+        className="flex min-w-0 flex-1 cursor-pointer items-baseline gap-2 rounded-none px-2 py-0.5 text-left text-sm"
+        onClick={() => onOpen(channel.id)}
+        type="button"
+      >
+        <span aria-hidden className="w-3 shrink-0 select-none">
+          {isHighlighted ? "▸" : ""}
+        </span>
+        <span
+          className={cn(
+            "min-w-0 flex-1 truncate",
+            isUnread ? "font-semibold" : "font-medium",
+          )}
+        >
+          # {channel.name}
+        </span>
+        {isUnread ? (
+          <span
+            className="shrink-0 self-center text-3xs leading-none text-primary"
+            data-testid="dev-mode-unread-dot"
+            role="img"
+            aria-label="unread"
+          >
+            ●
+          </span>
+        ) : null}
+        <span className="shrink-0 text-xs text-muted-foreground/60">
+          {formatRelativeTime(channel.lastMessageAt)}
+        </span>
+      </button>
+      <button
+        aria-label={
+          isPinned ? `Unpin # ${channel.name}` : `Pin # ${channel.name}`
+        }
+        className={cn(
+          "shrink-0 cursor-pointer px-1.5 py-0.5 text-xs text-muted-foreground/60 hover:text-foreground",
+          !isPinned && "opacity-0 group-hover:opacity-100",
+        )}
+        onClick={() => toggleChannelPinned(channel.id)}
+        type="button"
+      >
+        {isPinned ? "unpin" : "pin"}
+      </button>
+    </div>
+  );
+}
+
+/**
+ * Always-visible left channel list. The shell owns which channel is
+ * highlighted (↑/↓), what Enter/Escape do, and the draggable width (shared
+ * with the top bar so the header columns stay aligned); this renders a
+ * pinned section on top and all other chats beneath — both ordered by last
+ * activity, most recent first — with unread indicators and per-row pin
+ * toggles. Clicking a row opens the channel immediately.
+ */
+export function DevChannelNavigator({
+  groups,
+  unreadChannelIds,
+  highlightedId,
+  dimmed,
+  widthControls,
+  onOpen,
+}: {
+  /** Render-ordered groups; within each, most recent activity renders first. */
+  groups: ChannelGroup[];
+  unreadChannelIds: ReadonlySet<string>;
+  highlightedId: string | null;
+  /** True while a channel is focused — the list stays visible but recedes. */
+  dimmed: boolean;
+  /** Lifted to the shell so the top bar can mirror the navigator width. */
+  widthControls: NavigatorWidthControls;
+  onOpen: (channelId: string) => void;
+}) {
+  const isEmpty = groups.every((group) => group.channels.length === 0);
+  const { width, dragging, dividerProps } = widthControls;
+
+  return (
+    <div className="flex shrink-0" style={{ width }}>
+      <div
+        className={cn(
+          "flex min-w-0 flex-1 flex-col bg-background font-mono transition-opacity",
+          dimmed && "opacity-45",
+        )}
+        data-testid="dev-mode-channel-navigator"
+      >
+        <div className="min-h-0 flex-1 overflow-y-auto px-1 py-1">
+          {isEmpty ? (
+            <div className="px-2 py-1 text-sm text-muted-foreground/60">
+              no sessions yet
+            </div>
+          ) : null}
+          {groups.map((group) => (
+            <div key={group.pinned ? "pinned" : "chats"}>
+              {group.pinned ? (
+                <div className="select-none px-2 pb-0.5 pt-2 text-xs uppercase tracking-wide text-muted-foreground/50">
+                  pinned
+                </div>
+              ) : groups.length > 1 ? (
+                <div className="mt-2 border-t border-border/40 pt-1" />
+              ) : null}
+              {group.channels.map((channel) => (
+                <ChannelRow
+                  key={channel.id}
+                  channel={channel}
+                  isHighlighted={channel.id === highlightedId}
+                  isPinned={group.pinned}
+                  isUnread={unreadChannelIds.has(channel.id)}
+                  onOpen={onOpen}
+                />
+              ))}
+            </div>
+          ))}
+        </div>
+      </div>
+      {/* biome-ignore lint/a11y/useSemanticElements: <hr> cannot host the drag/keyboard resize handlers of a movable separator */}
+      <div
+        className={cn(
+          "w-1 shrink-0 cursor-col-resize bg-border/60 outline-none hover:bg-primary/60 focus-visible:bg-primary/60",
+          dragging && "bg-primary",
+        )}
+        data-testid="dev-mode-navigator-resize"
+        role="separator"
+        aria-orientation="vertical"
+        aria-valuenow={Math.round(width)}
+        tabIndex={0}
+        {...dividerProps}
+      />
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevChannelSuggestions.tsx b/desktop/src/features/dev-mode/ui/DevChannelSuggestions.tsx
new file mode 100644
index 0000000000..ae8ecab8f6
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevChannelSuggestions.tsx
@@ -0,0 +1,45 @@
+import type { ChannelRef } from "@/features/dev-mode/lib/channelRefs";
+import { cn } from "@/shared/lib/cn";
+
+/**
+ * `#channel` autocomplete popup anchored above a composer textarea. Mouse
+ * clicks accept without stealing focus from the textarea (mousedown is
+ * prevented), matching the keyboard-first composer conventions.
+ */
+export function DevChannelSuggestions({
+  suggestions,
+  selectedIndex,
+  onAccept,
+}: {
+  suggestions: ChannelRef[];
+  selectedIndex: number;
+  onAccept: (suggestion: ChannelRef) => void;
+}) {
+  return (
+    <div
+      className="absolute bottom-full left-0 z-10 mb-1 min-w-64 max-w-full border border-border bg-background font-mono text-sm shadow-md"
+      data-testid="dev-mode-channel-suggestions"
+    >
+      <div className="border-b border-border/60 px-2 py-0.5 text-xs text-muted-foreground">
+        link a channel · tab/enter: insert · esc: dismiss
+      </div>
+      {suggestions.map((suggestion, index) => (
+        <button
+          key={suggestion.id}
+          className={cn(
+            "flex w-full cursor-pointer items-baseline gap-1 px-2 py-0.5 text-left",
+            index === selectedIndex
+              ? "bg-muted text-foreground"
+              : "text-muted-foreground hover:bg-muted/50",
+          )}
+          onClick={() => onAccept(suggestion)}
+          onMouseDown={(event) => event.preventDefault()}
+          type="button"
+        >
+          <span className="select-none text-muted-foreground/60">#</span>
+          <span className="min-w-0 truncate">{suggestion.name}</span>
+        </button>
+      ))}
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevChannelTabs.tsx b/desktop/src/features/dev-mode/ui/DevChannelTabs.tsx
new file mode 100644
index 0000000000..798a353c69
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevChannelTabs.tsx
@@ -0,0 +1,94 @@
+import * as React from "react";
+
+import { parseSubChannelName } from "@/features/dev-mode/lib/subChannels";
+import type { Channel } from "@/shared/api/types";
+import { cn } from "@/shared/lib/cn";
+
+/**
+ * Tab strip across the top of an open channel: `main` plus one tab per
+ * sub-channel the user can see (surfaced to users as "tabs"). Parents can
+ * carry hundreds, so the strip scrolls horizontally instead of wrapping;
+ * the active tab scrolls itself into view. ⌘[/⌘] cycle through tabs.
+ */
+export function DevChannelTabs({
+  main,
+  subs,
+  activeId,
+  unreadChannelIds,
+  onSelect,
+  onNewSubChannel,
+}: {
+  main: Channel;
+  subs: Channel[];
+  activeId: string;
+  unreadChannelIds: ReadonlySet<string>;
+  onSelect: (channelId: string) => void;
+  onNewSubChannel: () => void;
+}) {
+  const scrollActiveIntoView = React.useCallback(
+    (node: HTMLButtonElement | null) => {
+      node?.scrollIntoView({ block: "nearest", inline: "nearest" });
+    },
+    [],
+  );
+
+  const tab = (channel: Channel, label: string) => {
+    const isActive = channel.id === activeId;
+    // An active tab keeps its dot while an unread thread remains inside it —
+    // viewing the tab clears top-level posts, not collapsed thread replies.
+    const isUnread = unreadChannelIds.has(channel.id);
+    return (
+      <button
+        key={channel.id}
+        ref={isActive ? scrollActiveIntoView : undefined}
+        className={cn(
+          "flex shrink-0 cursor-pointer items-baseline gap-1.5 border-b-2 px-2.5 py-1 text-xs",
+          isActive
+            ? "border-primary text-foreground"
+            : "border-transparent text-muted-foreground hover:text-foreground",
+        )}
+        data-testid="dev-mode-channel-tab"
+        data-active={isActive || undefined}
+        onClick={() => onSelect(channel.id)}
+        type="button"
+      >
+        <span className={cn("whitespace-nowrap", isUnread && "font-semibold")}>
+          {label}
+        </span>
+        {isUnread ? (
+          <span
+            aria-label="unread"
+            className="text-3xs leading-none text-primary"
+            role="img"
+          >
+            ●
+          </span>
+        ) : null}
+      </button>
+    );
+  };
+
+  return (
+    <div
+      className="flex shrink-0 items-center border-b border-border/60 font-mono"
+      data-testid="dev-mode-channel-tabs"
+    >
+      <div className="scrollbar-none flex min-w-0 flex-1 overflow-x-auto">
+        {tab(main, "main")}
+        {subs.map((sub) =>
+          tab(sub, parseSubChannelName(sub.name)?.subSlug ?? sub.name),
+        )}
+      </div>
+      <button
+        aria-label={`New tab in # ${main.name}`}
+        className="shrink-0 cursor-pointer px-2.5 py-1 text-xs text-muted-foreground/60 hover:text-foreground"
+        data-testid="dev-mode-new-tab"
+        onClick={onNewSubChannel}
+        title="⌘⇧T"
+        type="button"
+      >
+        + tab
+      </button>
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevCommandPalette.tsx b/desktop/src/features/dev-mode/ui/DevCommandPalette.tsx
new file mode 100644
index 0000000000..d48f944cdc
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevCommandPalette.tsx
@@ -0,0 +1,772 @@
+import * as React from "react";
+import { useNavigate } from "@tanstack/react-router";
+
+import { useQueryClient } from "@tanstack/react-query";
+
+import { attachManagedAgentToChannel } from "@/features/agents/channelAgents";
+import { useManagedAgentsQuery } from "@/features/agents/hooks";
+import {
+  invalidateChannelState,
+  useAddChannelMembersMutation,
+  useArchiveChannelMutation,
+  useChannelMembersQuery,
+  useJoinChannelMutation,
+  useLeaveChannelMutation,
+  useUpdateChannelMutation,
+} from "@/features/channels/hooks";
+import {
+  AUTHOR_COLOR_PALETTE,
+  defaultAuthorColor,
+  normalizeHexColor,
+  setNameColorOverride,
+  useAuthorColorResolver,
+} from "@/features/dev-mode/lib/authorColors";
+import { setDisplayStyle } from "@/features/dev-mode/lib/displayStylePreference";
+import {
+  toggleChannelPinned,
+  usePinnedChannels,
+} from "@/features/dev-mode/lib/pinnedChannels";
+import {
+  sanitizeChannelName,
+  uniqueChannelName,
+} from "@/features/dev-mode/lib/sessionNaming";
+import {
+  parseSubChannelName,
+  subChannelName,
+} from "@/features/dev-mode/lib/subChannels";
+import {
+  useFlattenedUserSearchResults,
+  useInfiniteUserSearchQuery,
+} from "@/features/profile/hooks";
+import type { SettingsSection } from "@/features/settings/ui/SettingsPanels";
+import type { Channel, UserSearchResult } from "@/shared/api/types";
+import { cn } from "@/shared/lib/cn";
+import { normalizePubkey, truncatePubkey } from "@/shared/lib/pubkey";
+
+type PaletteEntry = {
+  id: string;
+  label: string;
+  detail?: string;
+  /** Swatch color for color-picker entries. */
+  swatch?: string;
+  run: () => void;
+};
+
+type PaletteMode = "root" | "color" | "add-member" | "members" | "rename";
+
+/**
+ * Channels can have 1000+ members; the browser renders at most this many
+ * rows and tells the user to narrow by typing instead of scrolling.
+ */
+const MEMBERS_RENDER_CAP = 40;
+
+function formatCandidateName(user: UserSearchResult) {
+  return (
+    user.displayName?.trim() ||
+    user.nip05Handle?.trim() ||
+    truncatePubkey(user.pubkey)
+  );
+}
+
+const SETTINGS_ENTRIES: { section: SettingsSection; label: string }[] = [
+  { section: "agents", label: "configure agents" },
+  { section: "appearance", label: "appearance settings" },
+  { section: "profile", label: "profile settings" },
+  { section: "notifications", label: "notification settings" },
+  { section: "experimental", label: "experimental features" },
+  { section: "channel-templates", label: "channel templates" },
+  { section: "compute", label: "compute settings" },
+  { section: "updates", label: "check for updates" },
+];
+
+/**
+ * Amp-style command palette for developer mode: channel search across every
+ * session plus management/configuration actions. Opened with ⌘K anywhere
+ * in the shell, or `/` in an empty composer.
+ */
+export function DevCommandPalette({
+  channels,
+  discoverableChannels,
+  activeChannel,
+  parentOfActive,
+  myPubkey,
+  initialMode = "root",
+  onOpenChannel,
+  onNewSession,
+  onNewSubChannel,
+  onChannelLeft,
+  onShowShortcuts,
+  onClose,
+}: {
+  /** All session channels, newest first. */
+  channels: Channel[];
+  /** Open channels the user has not joined; searchable, enter joins. */
+  discoverableChannels: Channel[];
+  /** Channel that add-member/leave actions apply to (focused or previewed). */
+  activeChannel: Channel | null;
+  /** Set when the active channel is a `parent--sub` of an existing parent. */
+  parentOfActive: Channel | null;
+  myPubkey: string | null;
+  /** Open directly into a sub-view, e.g. the top bar's member count. */
+  initialMode?: "root" | "members";
+  onOpenChannel: (channelId: string) => void;
+  onNewSession: () => void;
+  /** Starts a sub-channel draft in the open channel; null when unavailable. */
+  onNewSubChannel: (() => void) | null;
+  onChannelLeft: (channelId: string) => void;
+  /** Opens the dev-mode keyboard-shortcuts pane. */
+  onShowShortcuts: () => void;
+  onClose: () => void;
+}) {
+  const navigate = useNavigate();
+  const queryClient = useQueryClient();
+  const [query, setQuery] = React.useState("");
+  const [mode, setMode] = React.useState<PaletteMode>(initialMode);
+  const [selectedIndex, setSelectedIndex] = React.useState(0);
+  const [actionError, setActionError] = React.useState<string | null>(null);
+  const inputRef = React.useRef<HTMLInputElement>(null);
+
+  React.useEffect(() => {
+    inputRef.current?.focus();
+  }, []);
+
+  const activeChannelId = activeChannel?.id ?? null;
+  const pinnedIds = usePinnedChannels();
+  const addMembersMutation = useAddChannelMembersMutation(activeChannelId);
+  const leaveMutation = useLeaveChannelMutation(activeChannelId);
+  const joinMutation = useJoinChannelMutation(null);
+  const archiveMutation = useArchiveChannelMutation(activeChannelId);
+  const updateChannelMutation = useUpdateChannelMutation(activeChannelId);
+  const membersQuery = useChannelMembersQuery(activeChannelId);
+  const resolveColor = useAuthorColorResolver();
+
+  // The relay refuses to remove a channel's last owner, so when no other
+  // human would remain, "leave" archives the channel instead.
+  const isLastHumanMember = React.useMemo(() => {
+    const members = membersQuery.data;
+    if (!members || !myPubkey) return false;
+    const self = normalizePubkey(myPubkey);
+    return !members.some(
+      (member) =>
+        normalizePubkey(member.pubkey) !== self &&
+        !member.isAgent &&
+        member.role !== "bot",
+    );
+  }, [membersQuery.data, myPubkey]);
+  const managedAgentsQuery = useManagedAgentsQuery({
+    enabled: mode === "add-member",
+  });
+  const userSearchQuery = useInfiniteUserSearchQuery(query, {
+    enabled: mode === "add-member" && query.trim().length >= 2,
+    limit: 20,
+  });
+  const userSearchResults = useFlattenedUserSearchResults(userSearchQuery.data);
+
+  const openSettings = React.useCallback(
+    (section: SettingsSection) => {
+      onClose();
+      void navigate({ to: "/settings", search: { section } });
+    },
+    [navigate, onClose],
+  );
+
+  // Close immediately and let the mutations run in the background — the
+  // channel hooks apply optimistic cache updates and roll back on failure,
+  // so the palette never blocks on a relay round trip.
+  const addUserToChannel = React.useCallback(
+    (user: UserSearchResult) => {
+      if (!activeChannelId) return;
+      setActionError(null);
+      // Local managed agents need a running harness pair, not just channel
+      // membership (see MembersSidebar) — route them through attach.
+      const managedAgent = (managedAgentsQuery.data ?? []).find(
+        (agent) =>
+          normalizePubkey(agent.pubkey) === normalizePubkey(user.pubkey),
+      );
+      if (managedAgent?.backend.type === "local") {
+        void attachManagedAgentToChannel(activeChannelId, {
+          agent: managedAgent,
+          ensureRunning: true,
+        })
+          .catch((error) => {
+            console.error("Failed to attach managed agent:", error);
+          })
+          .finally(() => {
+            void invalidateChannelState(queryClient, activeChannelId);
+          });
+      } else {
+        addMembersMutation.mutate(
+          {
+            pubkeys: [user.pubkey],
+            role: user.isAgent ? "bot" : "member",
+          },
+          {
+            onSuccess: (result) => {
+              if (result.errors.length > 0) {
+                console.error("Failed to add member:", result.errors[0]?.error);
+              }
+            },
+          },
+        );
+      }
+      onClose();
+    },
+    [
+      activeChannelId,
+      addMembersMutation,
+      managedAgentsQuery.data,
+      onClose,
+      queryClient,
+    ],
+  );
+
+  const leaveChannel = React.useCallback(() => {
+    if (!activeChannelId) return;
+    setActionError(null);
+    if (isLastHumanMember) {
+      archiveMutation.mutate();
+    } else {
+      leaveMutation.mutate();
+    }
+    onClose();
+    onChannelLeft(activeChannelId);
+  }, [
+    activeChannelId,
+    archiveMutation,
+    isLastHumanMember,
+    leaveMutation,
+    onChannelLeft,
+    onClose,
+  ]);
+
+  // Renaming a sub-channel only edits its suffix (the `parent--` prefix is
+  // the parent link); renaming a main cascades to its subs inside
+  // useUpdateChannelMutation.
+  const renameChannel = React.useCallback(
+    async (rawName: string) => {
+      if (!activeChannel) return;
+      const slug = sanitizeChannelName(rawName);
+      if (!slug) return;
+      const base = parentOfActive
+        ? subChannelName(parentOfActive.name, slug)
+        : slug;
+      const otherNames = new Set(
+        channels
+          .filter((channel) => channel.id !== activeChannel.id)
+          .map((channel) => channel.name),
+      );
+      const newName = uniqueChannelName(base, otherNames);
+      if (newName === activeChannel.name) {
+        onClose();
+        return;
+      }
+      setActionError(null);
+      try {
+        await updateChannelMutation.mutateAsync({ name: newName });
+        // The mutation invalidates with refetchType "none"; the mounted
+        // channel list must refetch now or cascaded sub renames stay stale
+        // and the family's tabs fall apart.
+        await invalidateChannelState(queryClient, activeChannel.id);
+        onClose();
+      } catch (error) {
+        setActionError(
+          error instanceof Error ? error.message : "Failed to rename channel.",
+        );
+      }
+    },
+    [
+      activeChannel,
+      channels,
+      onClose,
+      parentOfActive,
+      queryClient,
+      updateChannelMutation,
+    ],
+  );
+
+  const joinAndOpenChannel = React.useCallback(
+    (channelId: string) => {
+      setActionError(null);
+      joinMutation.mutate({ channelId });
+      onOpenChannel(channelId);
+      onClose();
+    },
+    [joinMutation, onClose, onOpenChannel],
+  );
+
+  const archiveChannel = React.useCallback(() => {
+    if (!activeChannelId) return;
+    setActionError(null);
+    archiveMutation.mutate();
+    onClose();
+    onChannelLeft(activeChannelId);
+  }, [activeChannelId, archiveMutation, onChannelLeft, onClose]);
+
+  const entries = React.useMemo<PaletteEntry[]>(() => {
+    const needle = query.trim().toLowerCase();
+
+    if (mode === "color") {
+      const colorEntries: PaletteEntry[] = AUTHOR_COLOR_PALETTE.map(
+        (color) => ({
+          id: `color-${color}`,
+          label: color,
+          swatch: color,
+          run: () => {
+            if (myPubkey) setNameColorOverride(myPubkey, color);
+            onClose();
+          },
+        }),
+      );
+      const typed = normalizeHexColor(needle);
+      if (typed) {
+        colorEntries.unshift({
+          id: "color-custom",
+          label: `use ${typed}`,
+          swatch: typed,
+          run: () => {
+            if (myPubkey) setNameColorOverride(myPubkey, typed);
+            onClose();
+          },
+        });
+      }
+      colorEntries.push({
+        id: "color-reset",
+        label: "reset to default",
+        swatch: myPubkey ? defaultAuthorColor(myPubkey) : undefined,
+        run: () => {
+          if (myPubkey) setNameColorOverride(myPubkey, null);
+          onClose();
+        },
+      });
+      return typed
+        ? colorEntries
+        : colorEntries.filter((entry) =>
+            entry.label.toLowerCase().includes(needle),
+          );
+    }
+
+    if (mode === "rename") {
+      if (!activeChannel) return [];
+      const slug = sanitizeChannelName(needle);
+      if (!slug) {
+        return [
+          {
+            id: "rename-hint",
+            label: "type a new name…",
+            detail: `renaming # ${activeChannel.name}`,
+            run: () => {},
+          },
+        ];
+      }
+      const preview = parentOfActive
+        ? subChannelName(parentOfActive.name, slug)
+        : slug;
+      return [
+        {
+          id: "rename-apply",
+          label: `rename to # ${preview}`,
+          detail: `was # ${activeChannel.name}`,
+          run: () => void renameChannel(needle),
+        },
+      ];
+    }
+
+    if (mode === "members") {
+      const members = membersQuery.data ?? [];
+      const matched = needle
+        ? members.filter((member) =>
+            `${member.displayName ?? ""} ${member.pubkey}`
+              .toLowerCase()
+              .includes(needle),
+          )
+        : members;
+      const memberEntries: PaletteEntry[] = matched
+        .slice(0, MEMBERS_RENDER_CAP)
+        .map((member) => ({
+          id: `member-${member.pubkey}`,
+          label: member.displayName || truncatePubkey(member.pubkey),
+          detail:
+            member.isAgent || member.role === "bot"
+              ? "agent"
+              : member.role !== "member"
+                ? member.role
+                : truncatePubkey(member.pubkey),
+          swatch: resolveColor(member.pubkey),
+          run: () => {},
+        }));
+      if (matched.length > MEMBERS_RENDER_CAP) {
+        memberEntries.push({
+          id: "members-overflow",
+          label: `… ${matched.length - MEMBERS_RENDER_CAP} more — type to narrow`,
+          run: () => {},
+        });
+      }
+      return memberEntries;
+    }
+
+    if (mode === "add-member") {
+      const memberPubkeys = new Set(
+        (membersQuery.data ?? []).map((member) =>
+          normalizePubkey(member.pubkey),
+        ),
+      );
+      // Sub-channel invariant: only parent members may join `parent--sub`.
+      const parentMemberPubkeys = parentOfActive
+        ? new Set(
+            parentOfActive.memberPubkeys.map((pubkey) =>
+              normalizePubkey(pubkey),
+            ),
+          )
+        : null;
+      return userSearchResults
+        .filter(
+          (user) =>
+            !memberPubkeys.has(normalizePubkey(user.pubkey)) &&
+            normalizePubkey(user.pubkey) !== normalizePubkey(myPubkey ?? "") &&
+            (parentMemberPubkeys?.has(normalizePubkey(user.pubkey)) ?? true),
+        )
+        .map((user) => ({
+          id: `add-${user.pubkey}`,
+          label: formatCandidateName(user),
+          detail: user.isAgent
+            ? "agent"
+            : (user.nip05Handle ?? truncatePubkey(user.pubkey)),
+          run: () => addUserToChannel(user),
+        }));
+    }
+
+    const channelActions: PaletteEntry[] = activeChannel
+      ? [
+          {
+            id: "view-members",
+            label: `view members of # ${activeChannel.name}`,
+            detail: `${activeChannel.memberCount} ${
+              activeChannel.memberCount === 1 ? "member" : "members"
+            }`,
+            run: () => {
+              setMode("members");
+              setQuery("");
+              setSelectedIndex(0);
+            },
+          },
+          {
+            id: "add-member",
+            label: `add someone to # ${activeChannel.name}`,
+            detail: parentOfActive
+              ? `members of # ${parentOfActive.name} only`
+              : "people & agents",
+            run: () => {
+              setMode("add-member");
+              setQuery("");
+              setSelectedIndex(0);
+            },
+          },
+          ...(onNewSubChannel
+            ? [
+                {
+                  id: "new-sub-channel",
+                  label: `new tab in # ${parentOfActive?.name ?? activeChannel.name}`,
+                  detail: "spawn a focused agent session · ⌘⇧T",
+                  run: () => {
+                    onNewSubChannel();
+                    onClose();
+                  },
+                } satisfies PaletteEntry,
+              ]
+            : []),
+          {
+            id: "rename-channel",
+            label: `rename # ${activeChannel.name}`,
+            detail: parentOfActive
+              ? "rename this tab"
+              : "its tabs are renamed with it",
+            run: () => {
+              setMode("rename");
+              setQuery("");
+              setSelectedIndex(0);
+            },
+          },
+          // Subs never appear in the left list, so pinning one is meaningless.
+          ...(parentOfActive
+            ? []
+            : [
+                {
+                  id: "pin-channel",
+                  label: pinnedIds.has(activeChannel.id)
+                    ? `unpin # ${activeChannel.name}`
+                    : `pin # ${activeChannel.name}`,
+                  detail: pinnedIds.has(activeChannel.id)
+                    ? "remove from pinned section"
+                    : "keep at the top of the channel list",
+                  run: () => {
+                    toggleChannelPinned(activeChannel.id);
+                    onClose();
+                  },
+                } satisfies PaletteEntry,
+              ]),
+          {
+            id: "leave-channel",
+            label: `leave # ${activeChannel.name}`,
+            detail: isLastHumanMember
+              ? "archives — you're the last member"
+              : "remove yourself",
+            run: () => leaveChannel(),
+          },
+          {
+            id: "archive-channel",
+            label: `archive # ${activeChannel.name}`,
+            detail: "hide from the channel list",
+            run: () => archiveChannel(),
+          },
+        ]
+      : [];
+
+    const actions: PaletteEntry[] = [
+      ...channelActions,
+      {
+        id: "new-session",
+        label: "new session",
+        detail: "fresh prompt",
+        run: () => {
+          onNewSession();
+          onClose();
+        },
+      },
+      {
+        id: "standard-ui",
+        label: "switch to standard ui",
+        detail: "⌘⇧D",
+        run: () => {
+          onClose();
+          setDisplayStyle("standard");
+        },
+      },
+      {
+        id: "name-color",
+        label: "set my name color",
+        detail: "hex or preset",
+        run: () => {
+          setMode("color");
+          setQuery("");
+          setSelectedIndex(0);
+        },
+      },
+      {
+        id: "shortcuts",
+        label: "keyboard shortcuts",
+        run: () => {
+          onClose();
+          onShowShortcuts();
+        },
+      },
+      ...SETTINGS_ENTRIES.map(
+        (entry): PaletteEntry => ({
+          id: `settings-${entry.section}`,
+          label: entry.label,
+          detail: "settings",
+          run: () => openSettings(entry.section),
+        }),
+      ),
+    ];
+
+    const channelEntries: PaletteEntry[] = channels.map((channel) => ({
+      id: `channel-${channel.id}`,
+      label: `# ${channel.name}`,
+      detail: channel.description ?? undefined,
+      run: () => {
+        onOpenChannel(channel.id);
+        onClose();
+      },
+    }));
+
+    if (!needle) return [...actions, ...channelEntries];
+
+    // Open channels the user hasn't joined only surface while searching —
+    // a relay can have hundreds and they'd drown the root list. Joining a
+    // `parent--sub` requires parent membership, so foreign subs are hidden.
+    const joinedNames = new Set(channels.map((channel) => channel.name));
+    const joinableEntries: PaletteEntry[] = discoverableChannels
+      .filter((channel) => {
+        const parsed = parseSubChannelName(channel.name);
+        return !parsed || joinedNames.has(parsed.parentName);
+      })
+      .map((channel) => ({
+        id: `join-${channel.id}`,
+        label: `# ${channel.name}`,
+        detail: "not joined · enter to join",
+        run: () => joinAndOpenChannel(channel.id),
+      }));
+
+    const matches = (entry: PaletteEntry) =>
+      `${entry.label} ${entry.detail ?? ""}`.toLowerCase().includes(needle);
+    const matchesName = (entry: PaletteEntry) =>
+      entry.label.toLowerCase().includes(needle);
+    // An action verb typed literally ("archive", "leave", "pin"…) beats
+    // channel-name substring hits; otherwise a query is usually a channel
+    // lookup, so channels rank above incidental action matches. Joined
+    // channels rank above joinable ones, which match on name only so
+    // typing "join" doesn't dump every discoverable channel.
+    const matchedActions = actions.filter(matches);
+    const startsWithNeedle = (entry: PaletteEntry) =>
+      entry.label.toLowerCase().startsWith(needle);
+    return [
+      ...matchedActions.filter(startsWithNeedle),
+      ...channelEntries.filter(matches),
+      ...joinableEntries.filter(matchesName),
+      ...matchedActions.filter((entry) => !startsWithNeedle(entry)),
+    ];
+  }, [
+    activeChannel,
+    addUserToChannel,
+    archiveChannel,
+    channels,
+    discoverableChannels,
+    isLastHumanMember,
+    joinAndOpenChannel,
+    leaveChannel,
+    membersQuery.data,
+    mode,
+    myPubkey,
+    onClose,
+    onNewSession,
+    onNewSubChannel,
+    onOpenChannel,
+    onShowShortcuts,
+    openSettings,
+    parentOfActive,
+    pinnedIds,
+    query,
+    renameChannel,
+    resolveColor,
+    userSearchResults,
+  ]);
+
+  const clampedIndex = Math.min(selectedIndex, Math.max(0, entries.length - 1));
+
+  const scrollSelectedIntoView = React.useCallback(
+    (node: HTMLButtonElement | null) => {
+      node?.scrollIntoView({ block: "nearest" });
+    },
+    [],
+  );
+
+  const handleKeyDown = (event: React.KeyboardEvent<HTMLInputElement>) => {
+    if (event.key === "Escape") {
+      event.preventDefault();
+      if (mode !== "root") {
+        setMode("root");
+        setQuery("");
+        setSelectedIndex(0);
+        setActionError(null);
+        return;
+      }
+      onClose();
+      return;
+    }
+    if (event.key === "ArrowDown") {
+      event.preventDefault();
+      setSelectedIndex(Math.min(clampedIndex + 1, entries.length - 1));
+      return;
+    }
+    if (event.key === "ArrowUp") {
+      event.preventDefault();
+      setSelectedIndex(Math.max(clampedIndex - 1, 0));
+      return;
+    }
+    if (event.key === "Enter") {
+      event.preventDefault();
+      entries[clampedIndex]?.run();
+    }
+  };
+
+  return (
+    <div
+      className="absolute inset-0 z-50 flex items-start justify-center pt-24 font-mono"
+      data-testid="dev-mode-palette"
+    >
+      <div
+        aria-hidden="true"
+        className="absolute inset-0 bg-background/60"
+        onClick={onClose}
+      />
+      <div className="relative flex max-h-[60vh] w-[560px] flex-col border border-border bg-background shadow-lg">
+        <input
+          ref={inputRef}
+          className="shrink-0 border-b border-border/60 bg-transparent px-3 py-2 text-sm outline-none placeholder:text-muted-foreground/60"
+          data-testid="dev-mode-palette-input"
+          onChange={(event) => {
+            setQuery(event.target.value);
+            setSelectedIndex(0);
+          }}
+          onKeyDown={handleKeyDown}
+          placeholder={
+            mode === "color"
+              ? "type a hex color or pick a preset…"
+              : mode === "add-member"
+                ? `search people & agents to add to # ${activeChannel?.name ?? ""}…`
+                : mode === "members"
+                  ? `search members of # ${activeChannel?.name ?? ""}…`
+                  : mode === "rename"
+                    ? `new name for # ${activeChannel?.name ?? ""}…`
+                    : "search channels and commands…"
+          }
+          spellCheck={false}
+          value={query}
+        />
+        {actionError ? (
+          <div className="shrink-0 border-b border-destructive/40 bg-destructive/10 px-3 py-1.5 text-xs text-destructive">
+            {actionError}
+          </div>
+        ) : null}
+        <div className="min-h-0 flex-1 overflow-y-auto py-1">
+          {entries.length === 0 ? (
+            <div className="px-3 py-2 text-sm text-muted-foreground/60">
+              {mode === "add-member"
+                ? query.trim().length < 2
+                  ? "type at least 2 characters to search…"
+                  : userSearchQuery.isFetching
+                    ? "searching…"
+                    : "no matches"
+                : mode === "members" && membersQuery.isLoading
+                  ? "loading members…"
+                  : "no matches"}
+            </div>
+          ) : null}
+          {entries.map((entry, index) => (
+            <button
+              key={entry.id}
+              ref={index === clampedIndex ? scrollSelectedIntoView : undefined}
+              className={cn(
+                "flex w-full cursor-pointer items-baseline gap-2 px-3 py-1 text-left text-sm",
+                index === clampedIndex
+                  ? "bg-primary/15 text-foreground"
+                  : "text-muted-foreground hover:bg-muted/40 hover:text-foreground",
+              )}
+              data-testid="dev-mode-palette-entry"
+              onClick={entry.run}
+              onMouseMove={() => setSelectedIndex(index)}
+              type="button"
+            >
+              {entry.swatch ? (
+                <span
+                  aria-hidden
+                  className="inline-block size-3 shrink-0 self-center border border-border/60"
+                  style={{ backgroundColor: entry.swatch }}
+                />
+              ) : null}
+              <span className="min-w-0 flex-1 truncate">{entry.label}</span>
+              {entry.detail ? (
+                <span className="max-w-48 shrink-0 truncate text-xs text-muted-foreground/60">
+                  {entry.detail}
+                </span>
+              ) : null}
+            </button>
+          ))}
+        </div>
+        <div className="shrink-0 border-t border-border/60 px-3 py-1.5 text-xs text-muted-foreground/60">
+          ↑↓: select · enter: run · esc: {mode === "root" ? "close" : "back"}
+        </div>
+      </div>
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevComposerAttachments.tsx b/desktop/src/features/dev-mode/ui/DevComposerAttachments.tsx
new file mode 100644
index 0000000000..02b00632a2
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevComposerAttachments.tsx
@@ -0,0 +1,74 @@
+import type { ImetaMedia } from "@/features/messages/lib/imetaMediaMarkdown";
+import type { UploadingAttachmentPreview } from "@/features/messages/lib/useMediaUpload";
+
+/**
+ * Pending and in-flight attachments for a dev-mode composer: compact,
+ * square-cornered chips in the terminal aesthetic. Images show a small
+ * thumbnail; videos and other files show their filename.
+ */
+export function DevComposerAttachments({
+  pendingImeta,
+  uploadingPreviews,
+  errorMessage,
+  onRemove,
+}: {
+  pendingImeta: ImetaMedia[];
+  uploadingPreviews: UploadingAttachmentPreview[];
+  errorMessage: string | null;
+  onRemove: (url: string) => void;
+}) {
+  if (
+    pendingImeta.length === 0 &&
+    uploadingPreviews.length === 0 &&
+    !errorMessage
+  ) {
+    return null;
+  }
+  return (
+    <div
+      className="flex flex-wrap items-center gap-2 px-4 pt-2 text-xs text-muted-foreground"
+      data-testid="dev-mode-attachments"
+    >
+      {pendingImeta.map((media) => (
+        <span
+          key={media.url}
+          className="flex items-center gap-1.5 border border-border/50 bg-muted/40 py-0.5 pr-1 pl-1.5"
+          data-testid="dev-mode-attachment-chip"
+        >
+          {media.type.startsWith("image/") ? (
+            <img
+              alt={media.filename ?? "attachment"}
+              className="h-8 w-8 object-cover"
+              src={media.url}
+            />
+          ) : null}
+          <span className="max-w-40 truncate">
+            {media.filename ??
+              (media.type.startsWith("video/") ? "video" : "file")}
+          </span>
+          <button
+            aria-label="remove attachment"
+            className="cursor-pointer px-1 text-muted-foreground hover:text-foreground"
+            onClick={() => onRemove(media.url)}
+            type="button"
+          >
+            ×
+          </button>
+        </span>
+      ))}
+      {uploadingPreviews.map((preview) => (
+        <span
+          key={preview.id}
+          className="border border-border/50 border-dashed px-1.5 py-0.5"
+          data-testid="dev-mode-attachment-uploading"
+        >
+          uploading {preview.filename ?? "file"}
+          {typeof preview.progress === "number" ? ` ${preview.progress}%` : "…"}
+        </span>
+      ))}
+      {errorMessage ? (
+        <span className="text-destructive">{errorMessage}</span>
+      ) : null}
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevComposerModeLine.tsx b/desktop/src/features/dev-mode/ui/DevComposerModeLine.tsx
new file mode 100644
index 0000000000..2ea8b33479
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevComposerModeLine.tsx
@@ -0,0 +1,42 @@
+import type { DevComposerMode } from "@/features/dev-mode/lib/useDevComposerModes";
+import { cn } from "@/shared/lib/cn";
+
+/**
+ * The composer's Tab-cycled target, rendered like a message's "to Name"
+ * direction line rather than a pill: sits at the top of the chat box, name in
+ * the agent's chat color.
+ */
+export function DevComposerModeLine({
+  mode,
+  busy,
+  agentColor,
+  className,
+}: {
+  mode: DevComposerMode;
+  busy: boolean;
+  agentColor: string | null;
+  className?: string;
+}) {
+  return (
+    <div
+      className={cn(
+        "select-none text-xs leading-4 text-muted-foreground/60",
+        className,
+      )}
+      data-testid="dev-mode-pill"
+    >
+      {busy ? (
+        "working…"
+      ) : mode.kind === "agent" ? (
+        <>
+          to{" "}
+          <span style={agentColor ? { color: agentColor } : undefined}>
+            {mode.target.name}
+          </span>
+        </>
+      ) : (
+        "chat"
+      )}
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevComposerResizeHandle.tsx b/desktop/src/features/dev-mode/ui/DevComposerResizeHandle.tsx
new file mode 100644
index 0000000000..05a55165c1
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevComposerResizeHandle.tsx
@@ -0,0 +1,38 @@
+import type * as React from "react";
+
+import { cn } from "@/shared/lib/cn";
+
+/**
+ * Horizontal drag strip along a composer's top edge. Doubles as the pane
+ * border; dragging (or ↑/↓ when focused) resizes the composer.
+ */
+export function DevComposerResizeHandle({
+  dragging,
+  testId,
+  "aria-valuenow": valueNow,
+  ...handlers
+}: {
+  dragging: boolean;
+  testId: string;
+  "aria-valuenow": number;
+  onPointerDown: (event: React.PointerEvent<HTMLDivElement>) => void;
+  onPointerMove: (event: React.PointerEvent<HTMLDivElement>) => void;
+  onPointerUp: (event: React.PointerEvent<HTMLDivElement>) => void;
+  onKeyDown: (event: React.KeyboardEvent<HTMLDivElement>) => void;
+}) {
+  return (
+    // biome-ignore lint/a11y/useSemanticElements: <hr> cannot host the drag/keyboard resize handlers of a movable separator
+    <div
+      className={cn(
+        "h-1 w-full shrink-0 cursor-row-resize bg-border/60 outline-none hover:bg-primary/60 focus-visible:bg-primary/60",
+        dragging && "bg-primary",
+      )}
+      data-testid={testId}
+      role="separator"
+      aria-orientation="horizontal"
+      aria-valuenow={valueNow}
+      tabIndex={0}
+      {...handlers}
+    />
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevLink.tsx b/desktop/src/features/dev-mode/ui/DevLink.tsx
new file mode 100644
index 0000000000..281767dc31
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevLink.tsx
@@ -0,0 +1,38 @@
+import { Link as LinkIcon } from "lucide-react";
+import { openUrl } from "@tauri-apps/plugin-opener";
+
+import { linkDisplayText } from "@/features/dev-mode/lib/linkDisplay";
+import { usePageTitle } from "@/features/dev-mode/lib/usePageTitle";
+
+/**
+ * Clickable transcript link: opens in the system browser and renders
+ * Slack-style — link icon plus an explicit markdown label when one was
+ * written, else the fetched page title, else the cleaned URL.
+ */
+export function DevLink({ href, label }: { href: string; label?: string }) {
+  const title = usePageTitle(label ? null : href);
+
+  // Plain inline display (not inline-flex): an atomic inline box would be
+  // skipped by native text selection (double-click-drag, triple-click), so
+  // the link must flow like ordinary text for selection and copy to include
+  // it. Long labels wrap with the rest of the message.
+  return (
+    <a
+      className="inline cursor-pointer break-words text-sky-500 hover:underline"
+      data-dev-link=""
+      href={href}
+      onClick={(event) => {
+        event.preventDefault();
+        void openUrl(href);
+      }}
+      rel="noreferrer"
+      title={href}
+    >
+      <LinkIcon
+        aria-hidden
+        className="mr-1 inline-block size-3.5 align-[-0.2em]"
+      />
+      {label ?? title ?? linkDisplayText(href)}
+    </a>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevMentionSuggestions.tsx b/desktop/src/features/dev-mode/ui/DevMentionSuggestions.tsx
new file mode 100644
index 0000000000..966a2fb56d
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevMentionSuggestions.tsx
@@ -0,0 +1,61 @@
+import { useAuthorColorResolver } from "@/features/dev-mode/lib/authorColors";
+import type { MentionSuggestion } from "@/features/dev-mode/lib/useMentionAutocomplete";
+import { cn } from "@/shared/lib/cn";
+
+/**
+ * `@user` autocomplete popup anchored above a composer textarea. Mouse
+ * clicks accept without stealing focus from the textarea (mousedown is
+ * prevented), matching the keyboard-first composer conventions.
+ */
+export function DevMentionSuggestions({
+  suggestions,
+  selectedIndex,
+  onAccept,
+}: {
+  suggestions: MentionSuggestion[];
+  selectedIndex: number;
+  onAccept: (suggestion: MentionSuggestion) => void;
+}) {
+  const resolveColor = useAuthorColorResolver();
+  return (
+    <div
+      className="absolute bottom-full left-0 z-10 mb-1 min-w-64 max-w-full border border-border bg-background font-mono text-sm shadow-md"
+      data-testid="dev-mode-mention-suggestions"
+    >
+      <div className="border-b border-border/60 px-2 py-0.5 text-xs text-muted-foreground">
+        tag someone · tab/enter: insert · esc: dismiss
+      </div>
+      {suggestions.map((suggestion, index) => (
+        <button
+          key={suggestion.pubkey}
+          className={cn(
+            "flex w-full cursor-pointer items-baseline gap-1 px-2 py-0.5 text-left",
+            index === selectedIndex
+              ? "bg-muted text-foreground"
+              : "text-muted-foreground hover:bg-muted/50",
+          )}
+          onClick={() => onAccept(suggestion)}
+          onMouseDown={(event) => event.preventDefault()}
+          type="button"
+        >
+          <span className="select-none text-muted-foreground/60">@</span>
+          <span
+            className="min-w-0 truncate"
+            style={{ color: resolveColor(suggestion.pubkey) }}
+          >
+            {suggestion.name}
+          </span>
+          {suggestion.isAgent ? (
+            <span className="ml-auto shrink-0 select-none text-xs text-muted-foreground/60">
+              agent
+            </span>
+          ) : !suggestion.isMember ? (
+            <span className="ml-auto shrink-0 select-none text-xs text-muted-foreground/60">
+              adds to channel
+            </span>
+          ) : null}
+        </button>
+      ))}
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevMessageRow.tsx b/desktop/src/features/dev-mode/ui/DevMessageRow.tsx
new file mode 100644
index 0000000000..04ada08233
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevMessageRow.tsx
@@ -0,0 +1,148 @@
+import * as React from "react";
+
+import type { AuthorColorResolver } from "@/features/dev-mode/lib/authorColors";
+import { useChannelRefs } from "@/features/dev-mode/lib/channelRefs";
+import { renderDevMarkdown } from "@/features/dev-mode/lib/devMarkdown";
+import {
+  matchLeadingMention,
+  type MentionStyle,
+} from "@/features/dev-mode/lib/highlightContent";
+import type { MessageReaction } from "@/features/dev-mode/lib/messageReactions";
+import type {
+  AgentResolver,
+  NameResolver,
+} from "@/features/dev-mode/lib/useMemberNameResolver";
+import type { RelayEvent } from "@/shared/api/types";
+import { KIND_SYSTEM_MESSAGE } from "@/shared/constants/kinds";
+import { cn } from "@/shared/lib/cn";
+import { parseImetaTags } from "@/shared/ui/markdown/parseImeta";
+
+function formatTime(createdAt: number) {
+  return new Date(createdAt * 1_000).toLocaleTimeString([], {
+    hour: "2-digit",
+    minute: "2-digit",
+  });
+}
+
+function ReactionChips({
+  reactions,
+  resolveName,
+}: {
+  reactions: MessageReaction[];
+  resolveName: NameResolver;
+}) {
+  const byEmoji = new Map<string, string[]>();
+  for (const { emoji, pubkey } of reactions) {
+    const bucket = byEmoji.get(emoji);
+    if (bucket) {
+      bucket.push(pubkey);
+    } else {
+      byEmoji.set(emoji, [pubkey]);
+    }
+  }
+  return (
+    <span className="flex shrink-0 select-none items-baseline gap-1 self-start">
+      {[...byEmoji.entries()].map(([emoji, pubkeys]) => (
+        <span
+          key={emoji}
+          className="text-xs text-muted-foreground"
+          title={[...new Set(pubkeys.map(resolveName))].join(", ")}
+        >
+          {emoji}
+          {pubkeys.length > 1 ? ` ${pubkeys.length}` : ""}
+        </span>
+      ))}
+    </span>
+  );
+}
+
+export function DevMessageRow({
+  event,
+  isSelf,
+  reactions,
+  resolveName,
+  resolveColor,
+  resolveIsAgent,
+}: {
+  event: RelayEvent;
+  isSelf: boolean;
+  /** Emoji reacted onto this message — agents react while working, so this doubles as the loading state. */
+  reactions?: MessageReaction[];
+  resolveName: NameResolver;
+  resolveColor: AuthorColorResolver;
+  resolveIsAgent: AgentResolver;
+}) {
+  const { channels, openChannel } = useChannelRefs();
+  // Stable per-event identity so the media renderer's memo holds.
+  const imetaByUrl = React.useMemo(
+    () => parseImetaTags(event.tags),
+    [event.tags],
+  );
+
+  if (event.kind === KIND_SYSTEM_MESSAGE) {
+    return null;
+  }
+
+  // The pubkeys this message explicitly mentions (its p tags) let known
+  // `@Name` tokens render as pills in the mentioned author's color.
+  const mentionStyles: MentionStyle[] = [];
+  for (const tag of event.tags) {
+    if (tag[0] !== "p" || !tag[1]) continue;
+    const name = resolveName(tag[1]);
+    if (mentionStyles.some((mention) => mention.name === name)) continue;
+    mentionStyles.push({ name, color: resolveColor(tag[1]) });
+  }
+
+  // A leading `@Name` mention on a human message is direction, not prose:
+  // it renders as a "to Name" line under the author instead of inside the
+  // message body. Agent replies keep their mentions inline as normal text.
+  const directed = resolveIsAgent(event.pubkey)
+    ? null
+    : matchLeadingMention(event.content, mentionStyles);
+  const bodyContent = directed
+    ? event.content.slice(directed.end)
+    : event.content;
+
+  return (
+    <div className="min-w-0 py-1 text-sm leading-6">
+      <div className="flex min-w-0 items-baseline gap-2">
+        <span
+          className={cn(
+            "shrink-0 font-medium",
+            isSelf && "underline decoration-dotted underline-offset-4",
+          )}
+          style={{ color: resolveColor(event.pubkey) }}
+        >
+          {resolveName(event.pubkey)}
+        </span>
+        {directed ? (
+          <span className="shrink-0 select-none text-xs text-muted-foreground/60">
+            to{" "}
+            <span style={{ color: directed.mention.color }}>
+              {directed.mention.name}
+            </span>
+          </span>
+        ) : null}
+        <span className="shrink-0 select-none text-xs text-muted-foreground/50">
+          {formatTime(event.created_at)}
+        </span>
+        {reactions && reactions.length > 0 ? (
+          <ReactionChips reactions={reactions} resolveName={resolveName} />
+        ) : null}
+      </div>
+      <div
+        className={cn(
+          "min-w-0 space-y-1 break-words [overflow-wrap:anywhere]",
+          event.pending && "text-muted-foreground",
+        )}
+      >
+        {renderDevMarkdown(
+          bodyContent,
+          mentionStyles,
+          { channels, onOpen: openChannel },
+          imetaByUrl,
+        )}
+      </div>
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevModeShell.tsx b/desktop/src/features/dev-mode/ui/DevModeShell.tsx
new file mode 100644
index 0000000000..55a152bc48
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevModeShell.tsx
@@ -0,0 +1,983 @@
+import * as React from "react";
+
+import { useAppShell } from "@/app/AppShellContext";
+
+import { useChannelsQuery } from "@/features/channels/hooks";
+import {
+  type ChannelRef,
+  DevChannelRefsProvider,
+} from "@/features/dev-mode/lib/channelRefs";
+import {
+  groupSessionChannels,
+  usePinnedChannels,
+} from "@/features/dev-mode/lib/pinnedChannels";
+import {
+  loadLastComposerModeKey,
+  storeLastComposerModeKey,
+} from "@/features/dev-mode/lib/composerModePreference";
+import { copySelectionWithLinkUrls } from "@/features/dev-mode/lib/copyLinkUrls";
+import type { MentionRecord } from "@/features/dev-mode/lib/mentionRecords";
+import {
+  aggregateLastActivity,
+  aggregateUnreadMains,
+  indexSubChannels,
+} from "@/features/dev-mode/lib/subChannels";
+import { selectRootEvents } from "@/features/dev-mode/lib/transcriptRoots";
+import { useShellFocusGuards } from "@/features/dev-mode/lib/useShellFocusGuards";
+import { useUnreadRouting } from "@/features/dev-mode/lib/useUnreadRouting";
+import {
+  devComposerModeLabel,
+  useDevComposerModes,
+  type DevComposerMode,
+} from "@/features/dev-mode/lib/useDevComposerModes";
+import { useDevSessionActions } from "@/features/dev-mode/lib/useDevSessionActions";
+import { useDevModeShortcuts } from "@/features/dev-mode/lib/useDevModeShortcuts";
+import { useNavigatorWidth } from "@/features/dev-mode/lib/useNavigatorWidth";
+import { DevChannelMembers } from "@/features/dev-mode/ui/DevChannelMembers";
+import { DevChannelNavigator } from "@/features/dev-mode/ui/DevChannelNavigator";
+import { DevChannelTabs } from "@/features/dev-mode/ui/DevChannelTabs";
+import { DevCommandPalette } from "@/features/dev-mode/ui/DevCommandPalette";
+import { DevPromptComposer } from "@/features/dev-mode/ui/DevPromptComposer";
+import { DevShortcutsOverlay } from "@/features/dev-mode/ui/DevShortcutsOverlay";
+import { DevSplitPane } from "@/features/dev-mode/ui/DevSplitPane";
+import { DevThreadPanel } from "@/features/dev-mode/ui/DevThreadPanel";
+import { DevTranscript } from "@/features/dev-mode/ui/DevTranscript";
+import { useChannelMessagesQuery } from "@/features/messages/hooks";
+import type { ImetaMedia } from "@/features/messages/lib/imetaMediaMarkdown";
+import { useIdentityQuery } from "@/shared/api/hooks";
+import { cn } from "@/shared/lib/cn";
+import { isMacPlatform } from "@/shared/lib/platform";
+import { normalizePubkey } from "@/shared/lib/pubkey";
+import { useIsFullscreen } from "@/shared/lib/useIsFullscreen";
+
+/**
+ * Stable identity for the cycled mode. Selection is keyed rather than
+ * indexed so agent list refreshes cannot silently retarget the next prompt
+ * at a different agent; a vanished agent falls back to the default agent.
+ */
+function devComposerModeKey(mode: DevComposerMode): string {
+  return mode.kind === "chat" ? "chat" : normalizePubkey(mode.target.pubkey);
+}
+
+/**
+ * Keyboard model:
+ *
+ * - `fresh` — just the composer. Enter spawns a session channel; ↑ slides
+ *   the channel navigator out from the left.
+ * - `navigator` — ↑/↓ preview channels (transcript shows behind), Enter
+ *   opens the highlighted channel, Escape returns to fresh.
+ * - `channel` — Enter sends; empty ↑/↓ walk prompt cards; Enter on a card
+ *   opens the split-screen side chat; Escape unwinds side chat → card →
+ *   navigator.
+ *
+ * ⌘K (anywhere) or `/` (empty composer) opens the command palette.
+ */
+type ShellView = "fresh" | "navigator" | "channel";
+
+export function DevModeShell({
+  unreadChannelIds,
+  topLevelUnreadChannelIds,
+  hasCommunityRail = false,
+}: {
+  /** Channels with anything unread, including relevant thread replies. */
+  unreadChannelIds: ReadonlySet<string>;
+  /** Channels with unread channel-level posts only. */
+  topLevelUnreadChannelIds: ReadonlySet<string>;
+  /** The community rail sits under the macOS traffic lights when present. */
+  hasCommunityRail?: boolean;
+}) {
+  const identityQuery = useIdentityQuery();
+  const channelsQuery = useChannelsQuery();
+  const isFullscreen = useIsFullscreen();
+  const modes = useDevComposerModes();
+  const { createSessionChannel, createSubChannel, sendToSession } =
+    useDevSessionActions(identityQuery.data);
+
+  const [view, setView] = React.useState<ShellView>("fresh");
+  const [input, setInput] = React.useState("");
+  const [modeKey, setModeKey] = React.useState<string | null>(
+    loadLastComposerModeKey,
+  );
+  const [activeSessionId, setActiveSessionId] = React.useState<string | null>(
+    null,
+  );
+  const [navigatorId, setNavigatorId] = React.useState<string | null>(null);
+  const [selectedRootId, setSelectedRootId] = React.useState<string | null>(
+    null,
+  );
+  const [threadOpen, setThreadOpen] = React.useState(false);
+  const [activePane, setActivePane] = React.useState<"main" | "thread">("main");
+  // When set, the composer's next Enter spawns a sub-channel of this main
+  // channel instead of posting to the open channel.
+  const [subDraftParentId, setSubDraftParentId] = React.useState<string | null>(
+    null,
+  );
+  const [paletteOpen, setPaletteOpen] = React.useState(false);
+  const [paletteInitialMode, setPaletteInitialMode] = React.useState<
+    "root" | "members"
+  >("root");
+  const [shortcutsOpen, setShortcutsOpen] = React.useState(false);
+  const [focusSignal, setFocusSignal] = React.useState(0);
+  const [busy, setBusy] = React.useState(false);
+  const [error, setError] = React.useState<string | null>(null);
+
+  const focusComposer = React.useCallback(() => {
+    setFocusSignal((current) => current + 1);
+  }, []);
+
+  // While a prompt card is selected the caret leaves the message box — the
+  // shell owns ↑/↓/Enter/Escape via a window listener until the selection
+  // clears (Escape, ↓ past the newest card, or a click on the box).
+  const cardSelectionActive =
+    view === "channel" && selectedRootId !== null && !threadOpen;
+
+  // The composer remembers the last target the user talked to (persisted
+  // across launches). Before any selection exists — or when the remembered
+  // agent vanishes — it falls back to the default: the first managed (local)
+  // agent, else the first agent; plain chat only when no agents exist.
+  const defaultModeIndex = React.useMemo(() => {
+    const managedIndex = modes.findIndex(
+      (candidate) =>
+        candidate.kind === "agent" && candidate.target.source === "managed",
+    );
+    if (managedIndex !== -1) return managedIndex;
+    const agentIndex = modes.findIndex(
+      (candidate) => candidate.kind === "agent",
+    );
+    return agentIndex === -1 ? 0 : agentIndex;
+  }, [modes]);
+
+  const foundModeIndex =
+    modeKey === null
+      ? -1
+      : modes.findIndex(
+          (candidate) => devComposerModeKey(candidate) === modeKey,
+        );
+  const modeIndex = foundModeIndex === -1 ? defaultModeIndex : foundModeIndex;
+  const mode = modes[modeIndex];
+
+  const sessions = React.useMemo(
+    () =>
+      (channelsQuery.data ?? []).filter(
+        (channel) =>
+          channel.channelType === "stream" &&
+          channel.isMember &&
+          channel.archivedAt === null,
+      ),
+    [channelsQuery.data],
+  );
+
+  // Open channels the user hasn't joined: the palette searches these and
+  // joins on enter, but they stay out of the left navigator until joined.
+  const discoverableChannels = React.useMemo(
+    () =>
+      (channelsQuery.data ?? []).filter(
+        (channel) =>
+          channel.channelType === "stream" &&
+          !channel.isMember &&
+          channel.visibility === "open" &&
+          channel.archivedAt === null,
+      ),
+    [channelsQuery.data],
+  );
+
+  // `#channel` references: composers autocomplete these names and message
+  // rows render matching tokens as clickable links to the channel.
+  const channelRefs = React.useMemo<ChannelRef[]>(
+    () => sessions.map((channel) => ({ id: channel.id, name: channel.name })),
+    [sessions],
+  );
+
+  // `parent--sub` channels pair with their parents: only mains render in
+  // the left list; subs surface as tabs inside their parent.
+  const subIndex = React.useMemo(() => indexSubChannels(sessions), [sessions]);
+
+  // The left list orders mains by their whole family's latest activity, so
+  // a busy sub-channel floats its parent.
+  const listChannels = React.useMemo(() => {
+    const overrides = aggregateLastActivity(subIndex);
+    if (overrides.size === 0) return subIndex.mains;
+    return subIndex.mains.map((channel) => {
+      const latest = overrides.get(channel.id);
+      return latest && latest > (channel.lastMessageAt ?? "")
+        ? { ...channel, lastMessageAt: latest }
+        : channel;
+    });
+  }, [subIndex]);
+
+  const navigatorUnreadIds = React.useMemo(
+    () => aggregateUnreadMains(subIndex, unreadChannelIds),
+    [subIndex, unreadChannelIds],
+  );
+
+  const pinnedIds = usePinnedChannels();
+  // Pinned chats on top, everything else below — each newest-first; `flat`
+  // matches the navigator's render order so ↑/↓ walk what is on screen.
+  const { groups: channelGroups, flat: orderedChannels } = React.useMemo(
+    () => groupSessionChannels(listChannels, pinnedIds),
+    [pinnedIds, listChannels],
+  );
+
+  const findChannel = React.useCallback(
+    (channelId: string | null) =>
+      (channelsQuery.data ?? []).find((channel) => channel.id === channelId) ??
+      null,
+    [channelsQuery.data],
+  );
+
+  const activeChannel =
+    view === "channel" ? findChannel(activeSessionId) : null;
+  const previewChannel = view === "navigator" ? findChannel(navigatorId) : null;
+  const topBarChannel = activeChannel ?? previewChannel;
+  // A stored id whose channel vanished (or is still propagating) renders as
+  // the fresh-session state; navigation starts from what is actually shown.
+  const effectiveSessionId = activeChannel?.id ?? null;
+
+  // Logical selection: the open channel's main. When a sub tab is active,
+  // the left list keeps highlighting the parent and ⌥↑↓/Escape navigate by
+  // parent; the transcript and composer stay on the physical channel.
+  const activeMainId = activeChannel
+    ? (subIndex.parentIdByChildId.get(activeChannel.id) ?? activeChannel.id)
+    : null;
+  const activeMainChannel = activeMainId ? findChannel(activeMainId) : null;
+  const activeSubChannels = React.useMemo(
+    () =>
+      activeMainId ? (subIndex.subsByParentId.get(activeMainId) ?? []) : [],
+    [activeMainId, subIndex],
+  );
+  const subDraftActive =
+    view === "channel" &&
+    subDraftParentId !== null &&
+    subDraftParentId === activeMainId;
+
+  // Shares the transcript's query cache — used only for card navigation.
+  const messagesQuery = useChannelMessagesQuery(activeChannel);
+  const roots = React.useMemo(
+    () => selectRootEvents(messagesQuery.data),
+    [messagesQuery.data],
+  );
+  const selectedRoot = roots.find((root) => root.id === selectedRootId) ?? null;
+
+  // Viewing an open channel marks its channel-level posts read (same passive
+  // NIP-RS path the standard channel screen uses). topLevelOnly keeps thread
+  // replies out of the marker — thread unread clears through what is actually
+  // seen: the inline first reply (transcript) and the side chat (panel).
+  const { markChannelRead } = useAppShell();
+  const latestRootAt =
+    roots.length > 0 ? roots[roots.length - 1].created_at : null;
+  const activeChannelIdForRead = activeChannel?.isMember
+    ? activeChannel.id
+    : null;
+  React.useEffect(() => {
+    if (!activeChannelIdForRead) return;
+    markChannelRead(
+      activeChannelIdForRead,
+      latestRootAt === null
+        ? null
+        : new Date(latestRootAt * 1_000).toISOString(),
+      { topLevelOnly: true },
+    );
+  }, [activeChannelIdForRead, latestRootAt, markChannelRead]);
+
+  // Card selection and the side chat belong to one channel's transcript.
+  // biome-ignore lint/correctness/useExhaustiveDependencies: intentional — selection resets only on channel switch
+  React.useEffect(() => {
+    setSelectedRootId(null);
+    setThreadOpen(false);
+    setActivePane("main");
+    setSubDraftParentId(null);
+  }, [effectiveSessionId]);
+
+  // Window refocus restores the last text input; dead-space clicks never
+  // blur it (see useShellFocusGuards).
+  const { handleFocusCapture, handleShellMouseDown, handleShellMouseUp } =
+    useShellFocusGuards({ cardSelectionActive, focusComposer });
+
+  // Lifted here (not inside the navigator) so the top bar's columns track
+  // the navigator width live while the divider is dragged.
+  const navigatorWidthControls = useNavigatorWidth();
+
+  const closePalette = React.useCallback(() => {
+    setPaletteOpen(false);
+    focusComposer();
+  }, [focusComposer]);
+
+  const openPalette = React.useCallback((mode: "root" | "members" = "root") => {
+    setPaletteInitialMode(mode);
+    setPaletteOpen(true);
+  }, []);
+
+  const closeShortcuts = React.useCallback(() => {
+    setShortcutsOpen(false);
+    focusComposer();
+  }, [focusComposer]);
+
+  const openChannel = React.useCallback(
+    (channelId: string) => {
+      setActiveSessionId(channelId);
+      // The left list only shows mains — highlight the family's parent when
+      // a sub tab is opened directly (palette, #ref link, tab click).
+      setNavigatorId(subIndex.parentIdByChildId.get(channelId) ?? channelId);
+      setView("channel");
+      focusComposer();
+    },
+    [focusComposer, subIndex],
+  );
+
+  const handleOpenThread = React.useCallback((rootId: string) => {
+    setSelectedRootId(rootId);
+    setThreadOpen(true);
+    setActivePane("thread");
+  }, []);
+
+  const openChannelAtUnread = useUnreadRouting({
+    subIndex,
+    unreadChannelIds,
+    topLevelUnreadChannelIds,
+    activeChannel,
+    roots,
+    openChannel,
+    openThread: handleOpenThread,
+  });
+
+  // "+ tab" (tab strip, palette, or ⌘⇧T): the composer's next Enter spawns
+  // a new tab (sub-channel) of the open main instead of posting to the
+  // channel.
+  const startSubChannelDraft = React.useCallback(() => {
+    if (!activeMainId) return;
+    setSubDraftParentId(activeMainId);
+    setSelectedRootId(null);
+    setThreadOpen(false);
+    setActivePane("main");
+    focusComposer();
+  }, [activeMainId, focusComposer]);
+
+  const goToFresh = React.useCallback(() => {
+    setView("fresh");
+    setActiveSessionId(null);
+    setThreadOpen(false);
+    setSelectedRootId(null);
+    setSubDraftParentId(null);
+    focusComposer();
+  }, [focusComposer]);
+
+  // Leaving/archiving a chat lands on the most recently active non-pinned
+  // chat (the departed channel may still be in the cached list, so exclude
+  // it); with nowhere to go, fall back to the fresh composer.
+  const handleChannelLeft = React.useCallback(
+    (leftChannelId: string) => {
+      // Leaving a sub tab returns to its parent's main tab.
+      const parentId = subIndex.parentIdByChildId.get(leftChannelId);
+      if (parentId) {
+        openChannel(parentId);
+        return;
+      }
+      const next = channelGroups
+        .find((group) => !group.pinned)
+        ?.channels.find((channel) => channel.id !== leftChannelId);
+      if (next) {
+        openChannel(next.id);
+      } else {
+        goToFresh();
+      }
+    },
+    [channelGroups, goToFresh, openChannel, subIndex],
+  );
+
+  // ⌘T's draft side chat: the pane opens with no thread yet; its first send
+  // posts a new message to the channel and attaches the pane to that thread.
+  const draftSideChat = React.useCallback(() => {
+    setSelectedRootId(null);
+    setThreadOpen(true);
+    setActivePane("thread");
+  }, []);
+
+  const togglePalette = React.useCallback(() => {
+    setPaletteInitialMode("root");
+    setPaletteOpen((current) => !current);
+  }, []);
+
+  useDevModeShortcuts({
+    view,
+    activeChannel,
+    activeMainChannel,
+    activeSubChannels,
+    onTogglePalette: togglePalette,
+    onNewSession: goToFresh,
+    onDraftSideChat:
+      view === "channel" && activeSessionId ? draftSideChat : null,
+    onDraftTab:
+      view === "channel" && activeMainId ? startSubChannelDraft : null,
+    onOpenChannel: openChannel,
+  });
+
+  const handleCycleMode = React.useCallback(
+    (direction: 1 | -1) => {
+      if (modes.length === 0) return;
+      const nextIndex = (modeIndex + direction + modes.length) % modes.length;
+      const nextKey = devComposerModeKey(modes[nextIndex]);
+      setModeKey(nextKey);
+      storeLastComposerModeKey(nextKey);
+    },
+    [modeIndex, modes],
+  );
+
+  const navigateChannels = React.useCallback(
+    (direction: 1 | -1) => {
+      if (orderedChannels.length === 0) return;
+      const currentIndex = orderedChannels.findIndex(
+        (session) => session.id === navigatorId,
+      );
+      if (currentIndex === -1) {
+        setNavigatorId(orderedChannels[orderedChannels.length - 1].id);
+        return;
+      }
+      // ↑ walks up the visible list; ↓ back down. The navigator stays
+      // highlighted at the ends — only Enter or Escape leave it.
+      const nextIndex = Math.min(
+        orderedChannels.length - 1,
+        Math.max(0, currentIndex + direction),
+      );
+      setNavigatorId(orderedChannels[nextIndex].id);
+    },
+    [navigatorId, orderedChannels],
+  );
+
+  // ⌥↑/⌥↓ from the composer: open the previous/next channel in the visible
+  // list directly — focus stays in the box the whole time.
+  const stepChannel = React.useCallback(
+    (direction: 1 | -1) => {
+      if (orderedChannels.length === 0) return;
+      const referenceId = view === "channel" ? activeMainId : navigatorId;
+      const currentIndex = orderedChannels.findIndex(
+        (session) => session.id === referenceId,
+      );
+      if (currentIndex === -1) {
+        // Nothing open — ⌥↑ enters the list at the bottom (nearest channel).
+        if (direction === -1) {
+          openChannel(orderedChannels[orderedChannels.length - 1].id);
+        }
+        return;
+      }
+      const nextIndex = Math.min(
+        orderedChannels.length - 1,
+        Math.max(0, currentIndex + direction),
+      );
+      if (nextIndex === currentIndex) return;
+      openChannel(orderedChannels[nextIndex].id);
+    },
+    [activeMainId, navigatorId, openChannel, orderedChannels, view],
+  );
+
+  const navigateCards = React.useCallback(
+    (direction: 1 | -1) => {
+      if (roots.length === 0) return;
+      const currentIndex = roots.findIndex(
+        (root) => root.id === selectedRootId,
+      );
+      if (currentIndex === -1) {
+        // ArrowUp enters the cards at the newest prompt; ArrowDown is a no-op.
+        if (direction === -1) {
+          setSelectedRootId(roots[roots.length - 1].id);
+        }
+        return;
+      }
+      const nextIndex = currentIndex + direction;
+      if (nextIndex >= roots.length) {
+        // Past the newest card — back to plain channel input.
+        setSelectedRootId(null);
+        setThreadOpen(false);
+        return;
+      }
+      setSelectedRootId(roots[Math.max(0, nextIndex)].id);
+    },
+    [roots, selectedRootId],
+  );
+
+  const handleNavigate = React.useCallback(
+    (direction: 1 | -1) => {
+      if (view === "channel") {
+        navigateCards(direction);
+        return;
+      }
+      if (view === "fresh") {
+        if (direction === -1) {
+          setView("navigator");
+          setNavigatorId(
+            orderedChannels.length > 0
+              ? orderedChannels[orderedChannels.length - 1].id
+              : null,
+          );
+        }
+        return;
+      }
+      navigateChannels(direction);
+    },
+    [navigateChannels, navigateCards, orderedChannels, view],
+  );
+
+  const handleEscape = React.useCallback(() => {
+    if (view === "channel") {
+      if (subDraftActive) {
+        setSubDraftParentId(null);
+        focusComposer();
+        return;
+      }
+      if (threadOpen) {
+        setThreadOpen(false);
+        setActivePane("main");
+        focusComposer();
+        return;
+      }
+      if (selectedRootId) {
+        setSelectedRootId(null);
+        return;
+      }
+      // Back out to the navigator with the current channel's main
+      // highlighted (subs have no row of their own).
+      setNavigatorId(activeMainId);
+      setActiveSessionId(null);
+      setView("navigator");
+      return;
+    }
+    if (view === "navigator") {
+      goToFresh();
+    }
+  }, [
+    activeMainId,
+    focusComposer,
+    goToFresh,
+    selectedRootId,
+    subDraftActive,
+    threadOpen,
+    view,
+  ]);
+
+  const handleSwitchPane = React.useCallback(
+    (pane: "main" | "thread") => {
+      if (!threadOpen) return;
+      setActivePane(pane);
+      if (pane === "main") {
+        focusComposer();
+      }
+    },
+    [focusComposer, threadOpen],
+  );
+
+  const handleSubmit = React.useCallback(
+    (mentions: MentionRecord[] = [], media: ImetaMedia[] = []) => {
+      const prompt = input.trim();
+      // A media-only send is a real send inside a channel; elsewhere the
+      // empty-input Enter keeps its navigation meaning (a fresh-composer
+      // channel needs prompt text for naming anyway).
+      const mediaOnlySend =
+        !prompt && media.length > 0 && view === "channel" && activeChannel;
+      if (!prompt && !mediaOnlySend) {
+        if (view === "navigator" && navigatorId) {
+          openChannelAtUnread(navigatorId);
+          return;
+        }
+        // Empty-input Enter opens the selected card's side chat.
+        if (view === "channel" && selectedRootId) {
+          handleOpenThread(selectedRootId);
+        }
+        return;
+      }
+      if (busy || !mode) return;
+
+      storeLastComposerModeKey(devComposerModeKey(mode));
+      setBusy(true);
+      setError(null);
+      setInput("");
+      void (async () => {
+        try {
+          let channel = activeChannel;
+          if (!channel) {
+            channel = await createSessionChannel(prompt, mode);
+            setActiveSessionId(channel.id);
+            setNavigatorId(channel.id);
+            setView("channel");
+          } else if (subDraftActive && activeMainChannel) {
+            // "+ sub" draft: spawn a sub-channel of the open main and land
+            // on its tab; the prompt goes to the new sub, not the main.
+            channel = await createSubChannel(activeMainChannel, prompt, mode);
+            setSubDraftParentId(null);
+            setActiveSessionId(channel.id);
+          }
+          await sendToSession(
+            channel,
+            prompt,
+            mode,
+            undefined,
+            mentions,
+            media,
+          );
+          // The conversation moved to the new prompt at the bottom.
+          setSelectedRootId(null);
+        } catch (submitError) {
+          setError(
+            submitError instanceof Error
+              ? submitError.message
+              : "Failed to send prompt.",
+          );
+          // Restore the failed prompt unless the user already typed on.
+          setInput((current) => (current === "" ? prompt : current));
+        } finally {
+          setBusy(false);
+        }
+      })();
+    },
+    [
+      activeChannel,
+      activeMainChannel,
+      busy,
+      createSessionChannel,
+      createSubChannel,
+      handleOpenThread,
+      input,
+      mode,
+      navigatorId,
+      openChannelAtUnread,
+      selectedRootId,
+      sendToSession,
+      subDraftActive,
+      view,
+    ],
+  );
+
+  const handleThreadSend = React.useCallback(
+    async (prompt: string, mentions: MentionRecord[], media: ImetaMedia[]) => {
+      if (!activeChannel || !mode) {
+        throw new Error("Thread is no longer available.");
+      }
+      storeLastComposerModeKey(devComposerModeKey(mode));
+      if (selectedRoot) {
+        await sendToSession(
+          activeChannel,
+          prompt,
+          mode,
+          selectedRoot.id,
+          mentions,
+          media,
+        );
+        return;
+      }
+      // Draft side chat (⌘T): the first send posts a root message to the
+      // channel exactly like the main composer, then the pane attaches to
+      // that new thread.
+      const newRoot = await sendToSession(
+        activeChannel,
+        prompt,
+        mode,
+        undefined,
+        mentions,
+        media,
+      );
+      setSelectedRootId(newRoot.id);
+    },
+    [activeChannel, mode, selectedRoot, sendToSession],
+  );
+
+  const placeholder = subDraftActive
+    ? `Prompt spawns a new tab in # ${activeMainChannel?.name ?? ""}…`
+    : activeChannel
+      ? mode?.kind === "agent"
+        ? `Message # ${activeChannel.name} and put ${devComposerModeLabel(mode)} to work…`
+        : `Message # ${activeChannel.name}…`
+      : mode?.kind === "agent"
+        ? `Prompt ${devComposerModeLabel(mode)} — spawns a new channel where it works…`
+        : "Start a discussion — spawns a new channel for humans…";
+
+  const composerActive =
+    !paletteOpen &&
+    !shortcutsOpen &&
+    !(threadOpen && activePane === "thread") &&
+    !cardSelectionActive;
+
+  React.useEffect(() => {
+    if (!cardSelectionActive || paletteOpen || shortcutsOpen) return;
+    const handleKeyDown = (event: KeyboardEvent) => {
+      if (event.metaKey || event.ctrlKey || event.altKey) return;
+      // A focused input owns its own keys (e.g. a click landed in one).
+      if (
+        event.target instanceof HTMLElement &&
+        event.target.matches("textarea, input, [contenteditable='true']")
+      ) {
+        return;
+      }
+      if (event.key === "ArrowUp" || event.key === "ArrowDown") {
+        event.preventDefault();
+        navigateCards(event.key === "ArrowUp" ? -1 : 1);
+      } else if (event.key === "Enter") {
+        event.preventDefault();
+        if (selectedRootId) handleOpenThread(selectedRootId);
+      } else if (event.key === "Escape") {
+        event.preventDefault();
+        handleEscape();
+      }
+    };
+    window.addEventListener("keydown", handleKeyDown);
+    return () => window.removeEventListener("keydown", handleKeyDown);
+  }, [
+    cardSelectionActive,
+    handleEscape,
+    handleOpenThread,
+    navigateCards,
+    paletteOpen,
+    selectedRootId,
+    shortcutsOpen,
+  ]);
+
+  const transcriptFor = (
+    channel: NonNullable<typeof activeChannel>,
+    { markRead = false } = {},
+  ) => (
+    <DevTranscript
+      channel={channel}
+      currentPubkey={identityQuery.data?.pubkey ?? null}
+      markRead={markRead}
+      onOpenThread={handleOpenThread}
+      selectedRootId={view === "channel" ? selectedRootId : null}
+    />
+  );
+
+  const sideChatOpen = Boolean(
+    view === "channel" && activeChannel && threadOpen && mode,
+  );
+
+  const composer = mode ? (
+    <DevPromptComposer
+      active={composerActive}
+      busy={busy}
+      channelId={activeChannel?.id ?? null}
+      draftLabel={
+        subDraftActive ? `new tab in # ${activeMainChannel?.name ?? ""}` : null
+      }
+      focusSignal={focusSignal}
+      mode={mode}
+      onChange={setInput}
+      onCycleMode={handleCycleMode}
+      onEscape={handleEscape}
+      onNavigate={handleNavigate}
+      onOpenPalette={() => openPalette()}
+      onOpenShortcuts={() => setShortcutsOpen(true)}
+      onStepChannel={stepChannel}
+      onReactivate={() => {
+        if (cardSelectionActive) setSelectedRootId(null);
+      }}
+      onSubmit={handleSubmit}
+      onSwitchPane={handleSwitchPane}
+      placeholder={placeholder}
+      selfPubkey={identityQuery.data?.pubkey ?? null}
+      value={input}
+    />
+  ) : null;
+
+  const errorBar = error ? (
+    <div className="border-t border-destructive/40 bg-destructive/10 px-4 py-1.5 font-mono text-xs text-destructive">
+      {error}
+    </div>
+  ) : null;
+
+  // Fixed px clearance: the native macOS traffic lights overlay this strip
+  // and ignore the app's text zoom, so rem-based padding would slide the
+  // title under them. The 56px community rail absorbs most of the lights'
+  // ~88px footprint, leaving ~32px protruding into the shell.
+  const macChrome = isMacPlatform() && !isFullscreen;
+  const titleClearance = macChrome
+    ? hasCommunityRail
+      ? "pl-[32px]"
+      : "pl-[88px]"
+    : "pl-4";
+
+  return (
+    <DevChannelRefsProvider channels={channelRefs} openChannel={openChannel}>
+      {/* biome-ignore lint/a11y/noStaticElementInteractions: handlers only guard focus (track last input, keep dead-space clicks from blurring it) — the div is not interactive */}
+      <div
+        className="relative flex min-h-0 min-w-0 flex-1 flex-col bg-background"
+        data-testid="dev-mode-shell"
+        onCopy={(event) => {
+          copySelectionWithLinkUrls(event.nativeEvent);
+        }}
+        onFocusCapture={handleFocusCapture}
+        onMouseDown={handleShellMouseDown}
+        onMouseUp={handleShellMouseUp}
+      >
+        {/* Two columns sharing the navigator's live width so "buzz ·
+            developer mode" sits over the channel list and the channel
+            name/members sit over the transcript, even mid-drag. */}
+        <div
+          className="flex h-[40px] shrink-0 cursor-default select-none items-center border-b border-border/60 font-mono text-xs text-muted-foreground"
+          data-tauri-drag-region
+        >
+          <div
+            className={cn("flex h-full shrink-0 items-center", titleClearance)}
+            data-tauri-drag-region
+            style={{ width: navigatorWidthControls.width }}
+          >
+            <span
+              className={cn(
+                "pointer-events-none truncate",
+                macChrome && "translate-y-[3px]",
+              )}
+            >
+              buzz · developer mode
+            </span>
+          </div>
+          <div
+            className="flex h-full min-w-0 flex-1 items-center justify-between gap-3 pr-4 pl-4"
+            data-tauri-drag-region
+          >
+            <span
+              className={cn(
+                "pointer-events-none min-w-0 truncate whitespace-nowrap text-foreground",
+                macChrome && "translate-y-[3px]",
+              )}
+              data-testid="dev-mode-topbar-channel"
+            >
+              {topBarChannel ? <># {topBarChannel.name}</> : null}
+            </span>
+            {topBarChannel ? (
+              <span
+                className={cn(
+                  "flex min-w-0 shrink-0 items-baseline",
+                  macChrome && "translate-y-[3px]",
+                )}
+              >
+                <DevChannelMembers
+                  channel={topBarChannel}
+                  onShowMembers={() => openPalette("members")}
+                />
+              </span>
+            ) : null}
+          </div>
+        </div>
+
+        <div className="flex min-h-0 min-w-0 flex-1">
+          <DevChannelNavigator
+            dimmed={view === "channel"}
+            groups={channelGroups}
+            highlightedId={view === "fresh" ? null : navigatorId}
+            onOpen={openChannelAtUnread}
+            unreadChannelIds={navigatorUnreadIds}
+            widthControls={navigatorWidthControls}
+          />
+
+          <div className="flex min-h-0 min-w-0 flex-1 flex-col">
+            {view === "channel" && activeChannel && activeMainChannel ? (
+              <DevChannelTabs
+                activeId={activeChannel.id}
+                main={activeMainChannel}
+                onNewSubChannel={startSubChannelDraft}
+                onSelect={openChannel}
+                subs={activeSubChannels}
+                unreadChannelIds={unreadChannelIds}
+              />
+            ) : null}
+            {view === "navigator" && previewChannel ? (
+              <div className="pointer-events-none flex min-h-0 min-w-0 flex-1 flex-col opacity-70">
+                <div className="shrink-0 border-b border-border/60 px-4 py-1 font-mono text-xs text-muted-foreground/60">
+                  preview
+                </div>
+                {transcriptFor(previewChannel)}
+              </div>
+            ) : view === "channel" && activeChannel ? (
+              threadOpen && mode ? (
+                <DevSplitPane
+                  activePane={activePane}
+                  main={
+                    <>
+                      {transcriptFor(activeChannel, {
+                        markRead: activeChannel.isMember,
+                      })}
+                      {composer}
+                    </>
+                  }
+                  side={
+                    <DevThreadPanel
+                      active={activePane === "thread"}
+                      channel={activeChannel}
+                      currentPubkey={identityQuery.data?.pubkey ?? null}
+                      mode={mode}
+                      onClose={() => {
+                        setThreadOpen(false);
+                        setActivePane("main");
+                        focusComposer();
+                      }}
+                      onCycleMode={handleCycleMode}
+                      onSend={handleThreadSend}
+                      onSwitchPane={handleSwitchPane}
+                      root={selectedRoot}
+                    />
+                  }
+                />
+              ) : (
+                transcriptFor(activeChannel, {
+                  markRead: activeChannel.isMember,
+                })
+              )
+            ) : (
+              <div className="flex min-h-0 flex-1 items-center justify-center px-8 font-mono text-sm text-muted-foreground">
+                <div className="max-w-lg space-y-2">
+                  <div className="text-foreground">new session</div>
+                  <div>
+                    Type a prompt — it spawns a channel and puts the selected
+                    target to work. Type ? for keyboard shortcuts.
+                  </div>
+                </div>
+              </div>
+            )}
+
+            {/* Inside a channel the composer covers only this pane; the fresh
+              and navigator states' composer below spans the full shell. */}
+            {view === "channel" && !sideChatOpen ? (
+              <>
+                {errorBar}
+                {composer}
+              </>
+            ) : null}
+            {sideChatOpen ? errorBar : null}
+          </div>
+        </div>
+
+        {view !== "channel" ? (
+          <>
+            {errorBar}
+            {composer}
+          </>
+        ) : null}
+
+        {paletteOpen ? (
+          <DevCommandPalette
+            activeChannel={topBarChannel}
+            channels={[...sessions].reverse()}
+            discoverableChannels={discoverableChannels}
+            initialMode={paletteInitialMode}
+            myPubkey={identityQuery.data?.pubkey ?? null}
+            onChannelLeft={handleChannelLeft}
+            onClose={closePalette}
+            onNewSession={goToFresh}
+            onShowShortcuts={() => setShortcutsOpen(true)}
+            onNewSubChannel={
+              view === "channel" && activeMainChannel
+                ? startSubChannelDraft
+                : null
+            }
+            onOpenChannel={openChannel}
+            parentOfActive={
+              topBarChannel
+                ? (findChannel(
+                    subIndex.parentIdByChildId.get(topBarChannel.id) ?? null,
+                  ) ?? null)
+                : null
+            }
+          />
+        ) : null}
+
+        {shortcutsOpen ? (
+          <DevShortcutsOverlay onClose={closeShortcuts} />
+        ) : null}
+      </div>
+    </DevChannelRefsProvider>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevPromptComposer.tsx b/desktop/src/features/dev-mode/ui/DevPromptComposer.tsx
new file mode 100644
index 0000000000..75d0831832
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevPromptComposer.tsx
@@ -0,0 +1,294 @@
+import * as React from "react";
+
+import { useAuthorColorResolver } from "@/features/dev-mode/lib/authorColors";
+import { cn } from "@/shared/lib/cn";
+import type { MentionRecord } from "@/features/dev-mode/lib/mentionRecords";
+import { useChannelRefAutocomplete } from "@/features/dev-mode/lib/useChannelRefAutocomplete";
+import { useComposerAutoGrow } from "@/features/dev-mode/lib/useComposerAutoGrow";
+import type { DevComposerMode } from "@/features/dev-mode/lib/useDevComposerModes";
+import { useMentionAutocomplete } from "@/features/dev-mode/lib/useMentionAutocomplete";
+import { DevChannelSuggestions } from "@/features/dev-mode/ui/DevChannelSuggestions";
+import { DevMentionSuggestions } from "@/features/dev-mode/ui/DevMentionSuggestions";
+import { DevComposerAttachments } from "@/features/dev-mode/ui/DevComposerAttachments";
+import { DevComposerModeLine } from "@/features/dev-mode/ui/DevComposerModeLine";
+import { DevComposerResizeHandle } from "@/features/dev-mode/ui/DevComposerResizeHandle";
+import type { ImetaMedia } from "@/features/messages/lib/imetaMediaMarkdown";
+import { useMediaUpload } from "@/features/messages/lib/useMediaUpload";
+
+type DevPromptComposerProps = {
+  value: string;
+  mode: DevComposerMode;
+  placeholder: string;
+  busy: boolean;
+  /** Whether this composer owns the keyboard (side chat may own it instead). */
+  active: boolean;
+  /**
+   * When set the composer is drafting something other than a channel message
+   * (e.g. a new tab) — renders a highlighted banner so the redirect is
+   * unmissable, not just placeholder text.
+   */
+  draftLabel?: string | null;
+  /** Increment to pull focus back here (e.g. after the palette closes). */
+  focusSignal: number;
+  /** Channel whose members rank first in `@` mention suggestions. */
+  channelId: string | null;
+  /** Excluded from mention suggestions. */
+  selfPubkey: string | null;
+  onChange: (value: string) => void;
+  /** Mentions are the `@Name`s still present in the submitted text. */
+  onSubmit: (mentions: MentionRecord[], media: ImetaMedia[]) => void;
+  /** Tab / Shift+Tab. */
+  onCycleMode: (direction: 1 | -1) => void;
+  /** ArrowUp / ArrowDown while the input is empty — channels or prompt cards. */
+  onNavigate: (direction: 1 | -1) => void;
+  /** ⌥ArrowUp / ⌥ArrowDown — switch channels without leaving the box. */
+  onStepChannel: (direction: 1 | -1) => void;
+  /** ArrowLeft / ArrowRight while the input is empty — side-chat pane focus. */
+  onSwitchPane: (pane: "main" | "thread") => void;
+  /** `/` on an empty input. */
+  onOpenPalette: () => void;
+  /** `?` on an empty input. */
+  onOpenShortcuts: () => void;
+  onEscape: () => void;
+  /** Click on the box while inactive — the user wants to type again. */
+  onReactivate?: () => void;
+};
+
+export function DevPromptComposer({
+  value,
+  mode,
+  placeholder,
+  busy,
+  active,
+  draftLabel = null,
+  focusSignal,
+  channelId,
+  selfPubkey,
+  onChange,
+  onSubmit,
+  onCycleMode,
+  onNavigate,
+  onStepChannel,
+  onSwitchPane,
+  onOpenPalette,
+  onOpenShortcuts,
+  onEscape,
+  onReactivate,
+}: DevPromptComposerProps) {
+  const { textareaRef, dragging, resizeHandleProps } = useComposerAutoGrow(
+    value,
+    "buzz.devMode.composerHeight",
+  );
+  const autocomplete = useChannelRefAutocomplete({
+    value,
+    onChange,
+    textareaRef,
+  });
+  const mentionAutocomplete = useMentionAutocomplete({
+    channelId,
+    selfPubkey,
+    value,
+    onChange,
+    textareaRef,
+  });
+  const resolveColor = useAuthorColorResolver();
+  // The pill (and caret) wear the same color the agent's name has in chat.
+  const agentColor =
+    mode.kind === "agent" ? resolveColor(mode.target.pubkey) : null;
+
+  // Pasted images/videos upload immediately and attach to the next send.
+  const {
+    handlePaste,
+    isUploading,
+    pendingImeta,
+    removeAttachment,
+    setPendingImeta,
+    uploadingPreviews,
+    uploadState,
+  } = useMediaUpload();
+
+  // biome-ignore lint/correctness/useExhaustiveDependencies: focusSignal is an intentional focus-pull trigger
+  React.useEffect(() => {
+    if (active) {
+      textareaRef.current?.focus();
+    } else {
+      // Inactive means something else owns the keyboard (card selection,
+      // side chat, palette) — the caret must leave the box.
+      textareaRef.current?.blur();
+    }
+  }, [active, focusSignal]);
+
+  const handleKeyDown = (event: React.KeyboardEvent<HTMLTextAreaElement>) => {
+    // Open `#channel` / `@user` suggestions own Tab/Enter/arrows/Escape.
+    if (autocomplete.handleKeyDown(event)) {
+      return;
+    }
+    if (mentionAutocomplete.handleKeyDown(event)) {
+      return;
+    }
+
+    if (event.key === "Tab") {
+      event.preventDefault();
+      onCycleMode(event.shiftKey ? -1 : 1);
+      return;
+    }
+
+    if (event.key === "Enter" && !event.shiftKey) {
+      event.preventDefault();
+      // An upload still in flight would silently miss the send — hold Enter
+      // until the attachment chips settle.
+      if (isUploading) return;
+      // Empty-input Enter is also meaningful (opens the highlighted channel
+      // or the selected card's side chat), so the shell decides; busy only
+      // blocks actual sends there.
+      onSubmit(mentionAutocomplete.extract(value), pendingImeta);
+      if (pendingImeta.length > 0) setPendingImeta([]);
+      return;
+    }
+
+    if (event.key === "Escape") {
+      event.preventDefault();
+      onEscape();
+      return;
+    }
+
+    if (event.key === "/" && !value) {
+      event.preventDefault();
+      onOpenPalette();
+      return;
+    }
+
+    if (event.key === "?" && !value) {
+      event.preventDefault();
+      onOpenShortcuts();
+      return;
+    }
+
+    if (event.key === "ArrowUp" || event.key === "ArrowDown") {
+      // ⌥↑/⌥↓ steps through the channel list, draft or not, without the
+      // caret ever leaving the box.
+      if (event.altKey) {
+        event.preventDefault();
+        onStepChannel(event.key === "ArrowUp" ? -1 : 1);
+        return;
+      }
+      if (!value) {
+        event.preventDefault();
+        onNavigate(event.key === "ArrowUp" ? -1 : 1);
+        return;
+      }
+    }
+
+    if ((event.key === "ArrowLeft" || event.key === "ArrowRight") && !value) {
+      event.preventDefault();
+      onSwitchPane(event.key === "ArrowLeft" ? "main" : "thread");
+    }
+  };
+
+  return (
+    <div
+      className={cn(
+        "bg-background/80 font-mono transition-opacity",
+        !active && "opacity-55",
+        draftLabel && "bg-primary/5",
+      )}
+    >
+      <DevComposerResizeHandle
+        dragging={dragging}
+        testId="dev-mode-composer-resize"
+        {...resizeHandleProps}
+      />
+      {/* Mirror the composer row's prefix so the mode line lines up exactly
+          with the textarea's left edge. A tab draft swaps the mode line for
+          the highlighted draft label in the same row, so entering and
+          leaving the draft never shifts the layout. */}
+      <div className="flex items-start gap-2 px-4 pt-2">
+        <span aria-hidden className="invisible select-none text-sm">
+          ⏵
+        </span>
+        {draftLabel ? (
+          <span
+            className="flex select-none items-baseline gap-2 text-xs leading-4 text-primary"
+            data-testid="dev-mode-draft-banner"
+          >
+            <span className="font-semibold">{draftLabel}</span>
+            <DevComposerModeLine
+              agentColor={agentColor}
+              busy={busy}
+              mode={mode}
+            />
+            <span className="text-primary/60">esc cancels</span>
+          </span>
+        ) : (
+          <DevComposerModeLine
+            agentColor={agentColor}
+            busy={busy}
+            mode={mode}
+          />
+        )}
+      </div>
+      <DevComposerAttachments
+        errorMessage={
+          uploadState.status === "error"
+            ? (uploadState.message ?? "upload failed")
+            : null
+        }
+        onRemove={removeAttachment}
+        pendingImeta={pendingImeta}
+        uploadingPreviews={uploadingPreviews}
+      />
+      <div className="relative flex items-start gap-2 px-4 pt-1 pb-3">
+        {active && autocomplete.open ? (
+          <DevChannelSuggestions
+            onAccept={autocomplete.accept}
+            selectedIndex={autocomplete.selectedIndex}
+            suggestions={autocomplete.suggestions}
+          />
+        ) : active && mentionAutocomplete.open ? (
+          <DevMentionSuggestions
+            onAccept={mentionAutocomplete.accept}
+            selectedIndex={mentionAutocomplete.selectedIndex}
+            suggestions={mentionAutocomplete.suggestions}
+          />
+        ) : null}
+        <span
+          aria-hidden
+          className={cn(
+            "select-none pt-[3px] text-sm",
+            !agentColor && "text-muted-foreground",
+          )}
+          style={agentColor ? { color: agentColor } : undefined}
+        >
+          ⏵
+        </span>
+        <textarea
+          ref={textareaRef}
+          className="min-h-6 w-full resize-none bg-transparent text-sm leading-6 outline-none placeholder:text-muted-foreground/60"
+          data-testid="dev-mode-composer"
+          onChange={(event) => {
+            onChange(event.target.value);
+            autocomplete.syncCursor(event.target);
+            mentionAutocomplete.syncCursor(event.target);
+          }}
+          onFocus={() => onSwitchPane("main")}
+          onKeyDown={handleKeyDown}
+          onMouseDown={() => {
+            if (!active) onReactivate?.();
+          }}
+          onPaste={(event) => {
+            if (event.clipboardData) void handlePaste(event);
+          }}
+          onSelect={(event) => {
+            autocomplete.syncCursor(event.currentTarget);
+            mentionAutocomplete.syncCursor(event.currentTarget);
+          }}
+          placeholder={placeholder}
+          readOnly={!active}
+          rows={1}
+          spellCheck={false}
+          value={value}
+        />
+      </div>
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevShortcutsOverlay.tsx b/desktop/src/features/dev-mode/ui/DevShortcutsOverlay.tsx
new file mode 100644
index 0000000000..fb3600a7cb
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevShortcutsOverlay.tsx
@@ -0,0 +1,97 @@
+import * as React from "react";
+
+const SHORTCUT_GROUPS: {
+  title: string;
+  shortcuts: { keys: string; action: string }[];
+}[] = [
+  {
+    title: "composer",
+    shortcuts: [
+      { keys: "tab / ⇧tab", action: "cycle target (chat ↔ agents)" },
+      { keys: "enter", action: "send · open highlighted channel or card" },
+      { keys: "↑ / ↓", action: "empty input: preview channels · walk prompts" },
+      { keys: "⌥↑ / ⌥↓", action: "switch channels without leaving the box" },
+      { keys: "← / →", action: "empty input: switch side-chat panes" },
+      { keys: "esc", action: "back — side chat → card → navigator" },
+      { keys: "/", action: "empty input: command palette" },
+      { keys: "?", action: "empty input: this pane" },
+    ],
+  },
+  {
+    title: "global",
+    shortcuts: [
+      { keys: "⌘K", action: "command palette" },
+      { keys: "⌘N", action: "new channel" },
+      { keys: "⌘T", action: "new side chat in the open channel" },
+      { keys: "⌘⇧T", action: "new tab (sub-channel)" },
+      { keys: "⌘[ / ⌘]", action: "previous / next tab" },
+      { keys: "⌘⇧D", action: "switch to standard ui" },
+    ],
+  },
+];
+
+/**
+ * Keyboard-shortcuts pane for developer mode. The shell keeps the UI free
+ * of key hints; this overlay (opened with `?` in an empty composer or via
+ * the palette's "keyboard shortcuts" entry) is the single reference.
+ */
+export function DevShortcutsOverlay({ onClose }: { onClose: () => void }) {
+  const panelRef = React.useRef<HTMLDivElement | null>(null);
+
+  React.useEffect(() => {
+    panelRef.current?.focus();
+  }, []);
+
+  return (
+    <div className="absolute inset-0 z-50 flex items-start justify-center bg-background/60 pt-[10vh] font-mono">
+      <div aria-hidden className="absolute inset-0" onClick={onClose} />
+      <div
+        ref={panelRef}
+        className="relative flex max-h-[70vh] w-[560px] flex-col border border-border bg-background shadow-lg outline-none"
+        data-testid="dev-mode-shortcuts-overlay"
+        onKeyDown={(event) => {
+          if (event.key === "Escape" || event.key === "Enter") {
+            event.preventDefault();
+            onClose();
+          }
+        }}
+        role="dialog"
+        aria-label="Keyboard shortcuts"
+        tabIndex={-1}
+      >
+        <div className="flex shrink-0 items-baseline justify-between border-b border-border/60 px-3 py-2 text-sm">
+          <span className="text-foreground">keyboard shortcuts</span>
+          <button
+            className="cursor-pointer text-xs text-muted-foreground hover:text-foreground"
+            onClick={onClose}
+            type="button"
+          >
+            close
+          </button>
+        </div>
+        <div className="min-h-0 flex-1 overflow-y-auto px-3 py-2">
+          {SHORTCUT_GROUPS.map((group) => (
+            <div key={group.title} className="pb-3">
+              <div className="pb-1 text-xs uppercase tracking-wide text-muted-foreground/50">
+                {group.title}
+              </div>
+              {group.shortcuts.map((shortcut) => (
+                <div
+                  key={shortcut.keys}
+                  className="flex items-baseline gap-3 py-0.5 text-sm"
+                >
+                  <span className="w-24 shrink-0 text-foreground">
+                    {shortcut.keys}
+                  </span>
+                  <span className="min-w-0 text-muted-foreground">
+                    {shortcut.action}
+                  </span>
+                </div>
+              ))}
+            </div>
+          ))}
+        </div>
+      </div>
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevSplitPane.tsx b/desktop/src/features/dev-mode/ui/DevSplitPane.tsx
new file mode 100644
index 0000000000..7872da6f12
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevSplitPane.tsx
@@ -0,0 +1,117 @@
+import * as React from "react";
+
+import { cn } from "@/shared/lib/cn";
+
+const STORAGE_KEY = "buzz.devMode.splitPct";
+const MIN_PCT = 25;
+const MAX_PCT = 75;
+
+function readStoredPct(): number {
+  try {
+    const raw = globalThis.localStorage?.getItem(STORAGE_KEY);
+    const value = raw === null || raw === undefined ? Number.NaN : Number(raw);
+    if (Number.isFinite(value)) {
+      return Math.min(MAX_PCT, Math.max(MIN_PCT, value));
+    }
+  } catch {
+    // Fall through to the default split.
+  }
+  return 50;
+}
+
+/**
+ * Channel transcript / side-chat split. The divider is pointer-draggable
+ * (clamped 25–75%, persisted per device) and the inactive pane dims so it is
+ * obvious which composer owns the keyboard.
+ */
+export function DevSplitPane({
+  main,
+  side,
+  activePane,
+}: {
+  main: React.ReactNode;
+  side: React.ReactNode;
+  activePane: "main" | "thread";
+}) {
+  const containerRef = React.useRef<HTMLDivElement>(null);
+  const [splitPct, setSplitPct] = React.useState(readStoredPct);
+  const [dragging, setDragging] = React.useState(false);
+
+  const handlePointerDown = (event: React.PointerEvent<HTMLDivElement>) => {
+    event.preventDefault();
+    event.currentTarget.setPointerCapture(event.pointerId);
+    setDragging(true);
+  };
+
+  const handlePointerMove = (event: React.PointerEvent<HTMLDivElement>) => {
+    if (!dragging) return;
+    const container = containerRef.current;
+    if (!container) return;
+    const bounds = container.getBoundingClientRect();
+    if (bounds.width === 0) return;
+    const pct = ((event.clientX - bounds.left) / bounds.width) * 100;
+    setSplitPct(Math.min(MAX_PCT, Math.max(MIN_PCT, pct)));
+  };
+
+  const handlePointerUp = (event: React.PointerEvent<HTMLDivElement>) => {
+    if (!dragging) return;
+    event.currentTarget.releasePointerCapture(event.pointerId);
+    setDragging(false);
+    try {
+      globalThis.localStorage?.setItem(STORAGE_KEY, String(splitPct));
+    } catch {
+      // Persistence is best-effort.
+    }
+  };
+
+  return (
+    <div ref={containerRef} className="flex min-h-0 min-w-0 flex-1">
+      <div
+        className={cn(
+          "flex min-h-0 min-w-0 flex-col transition-opacity",
+          activePane === "thread" && "opacity-55",
+        )}
+        style={{ width: `${splitPct}%` }}
+      >
+        {main}
+      </div>
+      {/* biome-ignore lint/a11y/useSemanticElements: <hr> cannot host the drag/keyboard resize handlers of a movable separator */}
+      <div
+        className={cn(
+          "w-1 shrink-0 cursor-col-resize bg-border/60 outline-none hover:bg-primary/60 focus-visible:bg-primary/60",
+          dragging && "bg-primary",
+        )}
+        data-testid="dev-mode-split-divider"
+        onKeyDown={(event) => {
+          if (event.key !== "ArrowLeft" && event.key !== "ArrowRight") return;
+          event.preventDefault();
+          const delta = event.key === "ArrowLeft" ? -2 : 2;
+          setSplitPct((current) => {
+            const next = Math.min(MAX_PCT, Math.max(MIN_PCT, current + delta));
+            try {
+              globalThis.localStorage?.setItem(STORAGE_KEY, String(next));
+            } catch {
+              // Persistence is best-effort.
+            }
+            return next;
+          });
+        }}
+        onPointerDown={handlePointerDown}
+        onPointerMove={handlePointerMove}
+        onPointerUp={handlePointerUp}
+        role="separator"
+        aria-orientation="vertical"
+        aria-valuenow={Math.round(splitPct)}
+        tabIndex={0}
+      />
+      <div
+        className={cn(
+          "flex min-h-0 min-w-0 flex-1 flex-col transition-opacity",
+          activePane === "main" && "opacity-55",
+        )}
+      >
+        {side}
+      </div>
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevThreadPanel.tsx b/desktop/src/features/dev-mode/ui/DevThreadPanel.tsx
new file mode 100644
index 0000000000..059c6e9d23
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevThreadPanel.tsx
@@ -0,0 +1,386 @@
+import * as React from "react";
+
+import { useAppShell } from "@/app/AppShellContext";
+import { useAuthorColorResolver } from "@/features/dev-mode/lib/authorColors";
+import { matchLeadingMention } from "@/features/dev-mode/lib/highlightContent";
+import { collectReactions } from "@/features/dev-mode/lib/messageReactions";
+import {
+  byCreatedAscending,
+  DEV_MESSAGE_KINDS,
+} from "@/features/dev-mode/lib/transcriptRoots";
+import {
+  devComposerModeLabel,
+  type DevComposerMode,
+} from "@/features/dev-mode/lib/useDevComposerModes";
+import type { MentionRecord } from "@/features/dev-mode/lib/mentionRecords";
+import { useChannelRefAutocomplete } from "@/features/dev-mode/lib/useChannelRefAutocomplete";
+import { useComposerAutoGrow } from "@/features/dev-mode/lib/useComposerAutoGrow";
+import { useMentionAutocomplete } from "@/features/dev-mode/lib/useMentionAutocomplete";
+import {
+  useMemberAgentResolver,
+  useMemberNameResolver,
+  type NameResolver,
+} from "@/features/dev-mode/lib/useMemberNameResolver";
+import { usePinnedScroll } from "@/features/dev-mode/lib/usePinnedScroll";
+import { DevChannelSuggestions } from "@/features/dev-mode/ui/DevChannelSuggestions";
+import { DevMentionSuggestions } from "@/features/dev-mode/ui/DevMentionSuggestions";
+import { DevComposerAttachments } from "@/features/dev-mode/ui/DevComposerAttachments";
+import { DevComposerModeLine } from "@/features/dev-mode/ui/DevComposerModeLine";
+import { DevComposerResizeHandle } from "@/features/dev-mode/ui/DevComposerResizeHandle";
+import { DevMessageRow } from "@/features/dev-mode/ui/DevMessageRow";
+import type { ImetaMedia } from "@/features/messages/lib/imetaMediaMarkdown";
+import { useMediaUpload } from "@/features/messages/lib/useMediaUpload";
+import { useThreadReplies } from "@/features/messages/useThreadReplies";
+import type { Channel, RelayEvent } from "@/shared/api/types";
+import { cn } from "@/shared/lib/cn";
+
+/** Header preview of the root prompt, minus any leading `@Name` direction. */
+function rootPreview(root: RelayEvent, resolveName: NameResolver): string {
+  const mentions = root.tags
+    .filter((tag) => tag[0] === "p" && tag[1])
+    .map((tag) => ({ name: resolveName(tag[1]), color: "" }));
+  const directed = matchLeadingMention(root.content, mentions);
+  return directed ? root.content.slice(directed.end) : root.content;
+}
+
+/**
+ * Split-screen side chat for one prompt card: the root prompt, its thread,
+ * and a composer that replies inside the thread so an agent picks the
+ * conversation up with that context. A null root is a draft side chat
+ * (⌘T): the first send posts a new message to the channel — exactly like
+ * the channel composer — and the pane attaches to that new thread.
+ */
+export function DevThreadPanel({
+  channel,
+  root,
+  mode,
+  currentPubkey,
+  active,
+  onCycleMode,
+  onSwitchPane,
+  onSend,
+  onClose,
+}: {
+  channel: Channel;
+  root: RelayEvent | null;
+  mode: DevComposerMode;
+  currentPubkey: string | null;
+  /** Whether this pane owns the keyboard (vs the main channel composer). */
+  active: boolean;
+  onCycleMode: (direction: 1 | -1) => void;
+  /** ArrowLeft / ArrowRight while the input is empty. */
+  onSwitchPane: (pane: "main" | "thread") => void;
+  /** Mentions are the `@Name`s still present in the sent text. */
+  onSend: (
+    prompt: string,
+    mentions: MentionRecord[],
+    media: ImetaMedia[],
+  ) => Promise<void>;
+  onClose: () => void;
+}) {
+  const repliesQuery = useThreadReplies(channel, root?.id ?? null);
+  const resolveName = useMemberNameResolver(channel.id);
+  const resolveColor = useAuthorColorResolver();
+  const resolveIsAgent = useMemberAgentResolver(channel.id);
+  const { scrollRef, contentRef, handleScroll } = usePinnedScroll(
+    root?.id ?? "draft",
+  );
+
+  const [input, setInput] = React.useState("");
+  const [busy, setBusy] = React.useState(false);
+  const [error, setError] = React.useState<string | null>(null);
+  const { textareaRef, dragging, resizeHandleProps } = useComposerAutoGrow(
+    input,
+    "buzz.devMode.threadComposerHeight",
+  );
+  const autocomplete = useChannelRefAutocomplete({
+    value: input,
+    onChange: setInput,
+    textareaRef,
+  });
+  const mentionAutocomplete = useMentionAutocomplete({
+    channelId: channel.id,
+    selfPubkey: currentPubkey,
+    value: input,
+    onChange: setInput,
+    textareaRef,
+  });
+
+  // biome-ignore lint/correctness/useExhaustiveDependencies: textareaRef is a stable ref from useComposerAutoGrow
+  React.useEffect(() => {
+    if (active) {
+      textareaRef.current?.focus();
+    }
+  }, [active]);
+
+  const replies = React.useMemo(
+    () =>
+      (repliesQuery.data ?? [])
+        .filter((event) => DEV_MESSAGE_KINDS.has(event.kind))
+        .sort(byCreatedAscending),
+    [repliesQuery.data],
+  );
+  const reactions = React.useMemo(
+    () => collectReactions(repliesQuery.data),
+    [repliesQuery.data],
+  );
+  const agentColor =
+    mode.kind === "agent" ? resolveColor(mode.target.pubkey) : null;
+
+  // The open side chat shows the whole thread, so advance the shared read
+  // frontier to the newest loaded reply — this is what clears the thread's
+  // contextual unread dots (card, tab, navigator) as replies stream in.
+  const { getThreadReadAt, markThreadRead } = useAppShell();
+  const rootId = root?.id ?? null;
+  const latestVisibleAt = React.useMemo(() => {
+    let latest = root?.created_at ?? 0;
+    for (const reply of replies) {
+      if (reply.created_at > latest) latest = reply.created_at;
+    }
+    return latest > 0 ? latest : null;
+  }, [replies, root]);
+  const channelId = channel.id;
+  React.useEffect(() => {
+    if (rootId === null || latestVisibleAt === null) return;
+    const readAt = getThreadReadAt(rootId, channelId);
+    if (readAt === null || readAt < latestVisibleAt) {
+      markThreadRead(rootId, latestVisibleAt);
+    }
+  }, [channelId, getThreadReadAt, latestVisibleAt, markThreadRead, rootId]);
+
+  // Pasted images/videos upload immediately and attach to the next send.
+  const {
+    handlePaste,
+    isUploading,
+    pendingImeta,
+    removeAttachment,
+    setPendingImeta,
+    uploadingPreviews,
+    uploadState,
+  } = useMediaUpload();
+
+  const handleSubmit = () => {
+    const prompt = input.trim();
+    if ((!prompt && pendingImeta.length === 0) || busy || isUploading) return;
+    const mentions = mentionAutocomplete.extract(prompt);
+    const media = pendingImeta;
+    setBusy(true);
+    setError(null);
+    setInput("");
+    setPendingImeta([]);
+    void (async () => {
+      try {
+        await onSend(prompt, mentions, media);
+      } catch (submitError) {
+        setError(
+          submitError instanceof Error
+            ? submitError.message
+            : "Failed to send reply.",
+        );
+        setInput((current) => (current === "" ? prompt : current));
+        setPendingImeta((current) => (current.length === 0 ? media : current));
+      } finally {
+        setBusy(false);
+      }
+    })();
+  };
+
+  const handleKeyDown = (event: React.KeyboardEvent<HTMLTextAreaElement>) => {
+    // Open `#channel` / `@user` suggestions own Tab/Enter/arrows/Escape.
+    if (autocomplete.handleKeyDown(event)) {
+      return;
+    }
+    if (mentionAutocomplete.handleKeyDown(event)) {
+      return;
+    }
+
+    if (event.key === "Tab") {
+      event.preventDefault();
+      onCycleMode(event.shiftKey ? -1 : 1);
+      return;
+    }
+    if (event.key === "Enter" && !event.shiftKey) {
+      event.preventDefault();
+      handleSubmit();
+      return;
+    }
+    if (event.key === "Escape") {
+      event.preventDefault();
+      onClose();
+      return;
+    }
+    if ((event.key === "ArrowLeft" || event.key === "ArrowRight") && !input) {
+      event.preventDefault();
+      onSwitchPane(event.key === "ArrowLeft" ? "main" : "thread");
+    }
+  };
+
+  return (
+    <div
+      className="flex min-h-0 min-w-0 flex-1 flex-col font-mono"
+      data-testid="dev-mode-thread-panel"
+    >
+      <div className="flex shrink-0 items-center justify-between border-b border-border/60 px-3 py-1.5 text-xs text-muted-foreground">
+        <span className="min-w-0 truncate">
+          side chat · {root ? rootPreview(root, resolveName) : "new thread"}
+        </span>
+        <button
+          className="ml-2 shrink-0 cursor-pointer hover:text-foreground"
+          onClick={onClose}
+          type="button"
+        >
+          esc ✕
+        </button>
+      </div>
+
+      <div
+        ref={scrollRef}
+        className="min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-3 py-2"
+        data-allow-text-selection
+        onScroll={handleScroll}
+      >
+        <div ref={contentRef}>
+          {root ? (
+            <>
+              <DevMessageRow
+                event={root}
+                isSelf={root.pubkey === currentPubkey}
+                reactions={reactions.get(root.id)}
+                resolveColor={resolveColor}
+                resolveIsAgent={resolveIsAgent}
+                resolveName={resolveName}
+              />
+              <div className="my-1 border-t border-border/40" />
+            </>
+          ) : (
+            <div className="py-0.5 text-sm text-muted-foreground/60">
+              new thread — your message posts to # {channel.name} and starts a
+              thread here
+            </div>
+          )}
+          {replies.map((reply) => (
+            <DevMessageRow
+              key={reply.localKey ?? reply.id}
+              event={reply}
+              isSelf={reply.pubkey === currentPubkey}
+              reactions={reactions.get(reply.id)}
+              resolveColor={resolveColor}
+              resolveIsAgent={resolveIsAgent}
+              resolveName={resolveName}
+            />
+          ))}
+          {repliesQuery.isLoading ? (
+            <div className="py-0.5 text-sm text-muted-foreground/60">
+              loading replies…
+            </div>
+          ) : null}
+          {repliesQuery.isError ? (
+            <button
+              className="cursor-pointer py-0.5 text-sm text-destructive hover:underline"
+              onClick={() => void repliesQuery.refetch()}
+              type="button"
+            >
+              failed to load replies — retry
+            </button>
+          ) : null}
+        </div>
+      </div>
+
+      {error ? (
+        <div className="border-t border-destructive/40 bg-destructive/10 px-3 py-1 text-xs text-destructive">
+          {error}
+        </div>
+      ) : null}
+
+      <div>
+        <DevComposerResizeHandle
+          dragging={dragging}
+          testId="dev-mode-thread-composer-resize"
+          {...resizeHandleProps}
+        />
+        {/* Mirror the composer row's prefix so the mode line lines up exactly
+            with the textarea's left edge. */}
+        <div className="flex items-start gap-2 px-3 pt-1">
+          <span aria-hidden className="invisible select-none text-sm">
+            ⏵
+          </span>
+          <DevComposerModeLine
+            agentColor={agentColor}
+            busy={busy}
+            mode={mode}
+          />
+        </div>
+        <DevComposerAttachments
+          errorMessage={
+            uploadState.status === "error"
+              ? (uploadState.message ?? "upload failed")
+              : null
+          }
+          onRemove={removeAttachment}
+          pendingImeta={pendingImeta}
+          uploadingPreviews={uploadingPreviews}
+        />
+        <div className="relative flex items-start gap-2 px-3 pt-1">
+          {active && autocomplete.open ? (
+            <DevChannelSuggestions
+              onAccept={autocomplete.accept}
+              selectedIndex={autocomplete.selectedIndex}
+              suggestions={autocomplete.suggestions}
+            />
+          ) : active && mentionAutocomplete.open ? (
+            <DevMentionSuggestions
+              onAccept={mentionAutocomplete.accept}
+              selectedIndex={mentionAutocomplete.selectedIndex}
+              suggestions={mentionAutocomplete.suggestions}
+            />
+          ) : null}
+          <span
+            aria-hidden
+            className={cn(
+              "select-none pt-[3px] text-sm",
+              !agentColor && "text-muted-foreground",
+            )}
+            style={agentColor ? { color: agentColor } : undefined}
+          >
+            ⏵
+          </span>
+          <textarea
+            ref={textareaRef}
+            className="min-h-6 w-full resize-none bg-transparent text-sm leading-6 outline-none placeholder:text-muted-foreground/60"
+            data-testid="dev-mode-thread-composer"
+            onChange={(event) => {
+              setInput(event.target.value);
+              autocomplete.syncCursor(event.target);
+              mentionAutocomplete.syncCursor(event.target);
+            }}
+            onFocus={() => onSwitchPane("thread")}
+            onKeyDown={handleKeyDown}
+            onPaste={handlePaste}
+            onSelect={(event) => {
+              autocomplete.syncCursor(event.currentTarget);
+              mentionAutocomplete.syncCursor(event.currentTarget);
+            }}
+            placeholder={
+              root
+                ? mode.kind === "agent"
+                  ? `Ask ${devComposerModeLabel(mode)} about this thread…`
+                  : "Reply in this thread…"
+                : mode.kind === "agent"
+                  ? `Prompt ${devComposerModeLabel(mode)} — starts a new thread in # ${channel.name}…`
+                  : `Start a new thread in # ${channel.name}…`
+            }
+            rows={1}
+            spellCheck={false}
+            value={input}
+          />
+        </div>
+        <div className="mt-1 flex items-center justify-end pr-3 pb-2 pl-9 text-xs text-muted-foreground">
+          <span className="select-none">
+            {root ? "enter: reply" : "enter: start thread"} · ←: channel · esc:
+            close
+          </span>
+        </div>
+      </div>
+    </div>
+  );
+}
diff --git a/desktop/src/features/dev-mode/ui/DevTranscript.tsx b/desktop/src/features/dev-mode/ui/DevTranscript.tsx
new file mode 100644
index 0000000000..c0663e5a19
--- /dev/null
+++ b/desktop/src/features/dev-mode/ui/DevTranscript.tsx
@@ -0,0 +1,460 @@
+import * as React from "react";
+
+import { useAppShell } from "@/app/AppShellContext";
+import {
+  useAuthorColorResolver,
+  type AuthorColorResolver,
+} from "@/features/dev-mode/lib/authorColors";
+import {
+  selectMembershipEvents,
+  type MembershipChange,
+} from "@/features/dev-mode/lib/membershipEvents";
+import {
+  collectReactions,
+  type MessageReaction,
+} from "@/features/dev-mode/lib/messageReactions";
+import {
+  byCreatedAscending,
+  DEV_MESSAGE_KINDS,
+  selectInlineVisibleCount,
+  selectRootEvents,
+} from "@/features/dev-mode/lib/transcriptRoots";
+import type {
+  AgentResolver,
+  NameResolver,
+} from "@/features/dev-mode/lib/useMemberNameResolver";
+import {
+  useMemberAgentResolver,
+  useMemberNameResolver,
+} from "@/features/dev-mode/lib/useMemberNameResolver";
+import { selectUnreadThreadRoots } from "@/features/dev-mode/lib/unreadThreads";
+import { usePinnedScroll } from "@/features/dev-mode/lib/usePinnedScroll";
+import { DevMessageRow } from "@/features/dev-mode/ui/DevMessageRow";
+import {
+  useChannelMessagesQuery,
+  useChannelSubscription,
+  useChannelWindowQuery,
+} from "@/features/messages/hooks";
+import {
+  channelWindowThreadSummaries,
+  type ChannelWindowThreadSummary,
+} from "@/features/messages/lib/channelWindowStore";
+import { useThreadReplies } from "@/features/messages/useThreadReplies";
+import type { Channel, RelayEvent } from "@/shared/api/types";
+import { cn } from "@/shared/lib/cn";
+
+/**
+ * The channel view shows the leading run of agent replies — everything
+ * the agent said before a human responded — inline; once a human replies,
+ * that message and everything after it lives in the side chat, collapsed
+ * here into a "… N more replies" affordance. A thread whose first reply
+ * is human still shows that one reply inline so prompts never render
+ * without their first response.
+ */
+function ThreadInlineReplies({
+  channel,
+  rootId,
+  replyCount,
+  unread,
+  markRead,
+  currentPubkey,
+  resolveName,
+  resolveColor,
+  resolveIsAgent,
+  onOpenThread,
+}: {
+  channel: Channel;
+  rootId: string;
+  replyCount: number;
+  unread: boolean;
+  /** Whether rendering the inline reply advances the thread read frontier. */
+  markRead: boolean;
+  currentPubkey: string | null;
+  resolveName: NameResolver;
+  resolveColor: AuthorColorResolver;
+  resolveIsAgent: AgentResolver;
+  onOpenThread: () => void;
+}) {
+  const repliesQuery = useThreadReplies(channel, rootId);
+  const replies = React.useMemo(
+    () =>
+      (repliesQuery.data ?? [])
+        .filter((event) => DEV_MESSAGE_KINDS.has(event.kind))
+        .sort(byCreatedAscending),
+    [repliesQuery.data],
+  );
+  // Thread fetches include their reaction aux events (see useThreadReplies).
+  const reactions = React.useMemo(
+    () => collectReactions(repliesQuery.data),
+    [repliesQuery.data],
+  );
+
+  const visible = React.useMemo(
+    () => replies.slice(0, selectInlineVisibleCount(replies, resolveIsAgent)),
+    [replies, resolveIsAgent],
+  );
+  // The summary count can outrun the fetched subtree (live recounts) —
+  // trust whichever knows about more replies.
+  const moreCount = Math.max(replyCount, replies.length) - visible.length;
+
+  // The inline replies are on screen, so seeing the channel counts as
+  // reading them: advance the thread frontier through the last visible
+  // reply. Later (collapsed) replies stay unread until the side chat is
+  // opened.
+  const { getThreadReadAt, markThreadRead } = useAppShell();
+  const lastVisibleAt = visible.at(-1)?.created_at ?? null;
+  const channelId = channel.id;
+  React.useEffect(() => {
+    if (!markRead || lastVisibleAt === null) return;
+    const readAt = getThreadReadAt(rootId, channelId);
+    if (readAt === null || readAt < lastVisibleAt) {
+      markThreadRead(rootId, lastVisibleAt);
+    }
+  }, [
+    channelId,
+    lastVisibleAt,
+    getThreadReadAt,
+    markRead,
+    markThreadRead,
+    rootId,
+  ]);
+
+  // The replies sit on the same indent as the prompt that produced them.
+  return (
+    <div className="mt-1">
+      {visible.length > 0 ? (
+        visible.map((reply) => (
+          <DevMessageRow
+            key={reply.localKey ?? reply.id}
+            event={reply}
+            isSelf={reply.pubkey === currentPubkey}
+            reactions={reactions.get(reply.id)}
+            resolveColor={resolveColor}
+            resolveIsAgent={resolveIsAgent}
+            resolveName={resolveName}
+          />
+        ))
+      ) : repliesQuery.isLoading ? (
+        <div className="py-0.5 text-sm text-muted-foreground/60">
+          loading reply…
+        </div>
+      ) : null}
+      {repliesQuery.isError ? (
+        <button
+          className="cursor-pointer py-0.5 text-sm text-destructive hover:underline"
+          onClick={() => void repliesQuery.refetch()}
+          type="button"
+        >
+          failed to load replies — retry
+        </button>
+      ) : moreCount > 0 ? (
+        <button
+          className={cn(
+            "mt-1 cursor-pointer py-0.5 text-sm",
+            unread
+              ? "text-primary hover:text-primary/80"
+              : "text-muted-foreground hover:text-foreground",
+          )}
+          data-testid="dev-mode-more-replies"
+          data-unread={unread || undefined}
+          onClick={(event) => {
+            event.stopPropagation();
+            onOpenThread();
+          }}
+          type="button"
+        >
+          … {moreCount} more {moreCount === 1 ? "reply" : "replies"}
+          {unread ? " ●" : ""}
+        </button>
+      ) : null}
+    </div>
+  );
+}
+
+function MembershipRow({
+  change,
+  resolveName,
+  resolveColor,
+}: {
+  change: MembershipChange;
+  resolveName: NameResolver;
+  resolveColor: AuthorColorResolver;
+}) {
+  const name = (pubkey: string) => (
+    <span style={{ color: resolveColor(pubkey) }}>{resolveName(pubkey)}</span>
+  );
+  return (
+    <div
+      className="mb-2 select-none px-3 text-xs text-muted-foreground/70"
+      data-testid="dev-mode-membership-row"
+    >
+      {change.change === "left" || change.change === "removed" ? "← " : "→ "}
+      {name(change.member)}{" "}
+      {change.change === "joined" ? (
+        "joined"
+      ) : change.change === "added" && change.actor ? (
+        <>added by {name(change.actor)}</>
+      ) : change.change === "added" ? (
+        "joined"
+      ) : change.change === "left" ? (
+        "left"
+      ) : change.actor ? (
+        <>removed by {name(change.actor)}</>
+      ) : (
+        "removed"
+      )}
+    </div>
+  );
+}
+
+function PromptCard({
+  channel,
+  root,
+  rootReactions,
+  replyCount,
+  unread,
+  markRead,
+  selected,
+  currentPubkey,
+  resolveName,
+  resolveColor,
+  resolveIsAgent,
+  onOpenThread,
+}: {
+  channel: Channel;
+  root: RelayEvent;
+  rootReactions: MessageReaction[] | undefined;
+  replyCount: number;
+  unread: boolean;
+  markRead: boolean;
+  selected: boolean;
+  currentPubkey: string | null;
+  resolveName: NameResolver;
+  resolveColor: AuthorColorResolver;
+  resolveIsAgent: AgentResolver;
+  onOpenThread: () => void;
+}) {
+  // Callback ref mounts only on the selected card, so keyboard navigation
+  // scrolls the newly selected card into view without an effect.
+  const scrollSelectedIntoView = React.useCallback(
+    (node: HTMLDivElement | null) => {
+      node?.scrollIntoView({ block: "nearest" });
+    },
+    [],
+  );
+
+  return (
+    // Selection is keyboard-only (↑/↓ + Enter on the composer); clicks land
+    // here only for text selection and never move focus or selection.
+    <div
+      ref={selected ? scrollSelectedIntoView : undefined}
+      className={cn(
+        // The border is transparent until keyboard focus so nothing shifts
+        // when ↑/↓ start walking the prompts.
+        "relative mb-2 rounded-none border px-3 py-2",
+        selected ? "border-primary/60 bg-primary/5" : "border-transparent",
+      )}
+      data-testid="dev-mode-prompt-card"
+    >
+      {/* Absolute so selecting a card never changes its height (no layout
+          shift while ↑/↓ walk the prompts). */}
+      {selected || unread ? (
+        <div className="pointer-events-none absolute right-1 top-1 flex select-none items-center gap-1.5 bg-background/90 px-1 text-xs text-primary/80">
+          {selected ? <span>⏎ side chat</span> : null}
+          {unread ? (
+            <span
+              aria-label="unread thread"
+              className="text-3xs leading-none text-primary"
+              data-testid="dev-mode-card-unread-dot"
+              role="img"
+            >
+              ●
+            </span>
+          ) : null}
+        </div>
+      ) : null}
+      <DevMessageRow
+        event={root}
+        isSelf={root.pubkey === currentPubkey}
+        reactions={rootReactions}
+        resolveColor={resolveColor}
+        resolveIsAgent={resolveIsAgent}
+        resolveName={resolveName}
+      />
+      {replyCount > 0 ? (
+        <ThreadInlineReplies
+          channel={channel}
+          currentPubkey={currentPubkey}
+          markRead={markRead}
+          onOpenThread={onOpenThread}
+          replyCount={replyCount}
+          resolveColor={resolveColor}
+          resolveIsAgent={resolveIsAgent}
+          resolveName={resolveName}
+          rootId={root.id}
+          unread={unread}
+        />
+      ) : null}
+    </div>
+  );
+}
+
+export function DevTranscript({
+  channel,
+  currentPubkey,
+  selectedRootId,
+  markRead,
+  onOpenThread,
+}: {
+  channel: Channel;
+  currentPubkey: string | null;
+  selectedRootId: string | null;
+  /** False for previews — looking at a preview must not advance read state. */
+  markRead: boolean;
+  onOpenThread: (rootId: string) => void;
+}) {
+  const messagesQuery = useChannelMessagesQuery(channel);
+  const windowQuery = useChannelWindowQuery(channel);
+  useChannelSubscription(channel);
+  const { getThreadReadAt, readStateVersion } = useAppShell();
+
+  const { scrollRef, contentRef, handleScroll } = usePinnedScroll(channel.id);
+
+  const roots = React.useMemo(
+    () => selectRootEvents(messagesQuery.data),
+    [messagesQuery.data],
+  );
+  const memberships = React.useMemo(
+    () => selectMembershipEvents(messagesQuery.data),
+    [messagesQuery.data],
+  );
+
+  // Membership rows can name people who already left — resolve those via
+  // the profile fallback rather than the (current-only) member list.
+  const membershipPubkeys = React.useMemo(
+    () => [
+      ...new Set(
+        memberships.flatMap((change) =>
+          change.actor ? [change.member, change.actor] : [change.member],
+        ),
+      ),
+    ],
+    [memberships],
+  );
+  const resolveName = useMemberNameResolver(channel.id, membershipPubkeys);
+  const resolveColor = useAuthorColorResolver();
+  const resolveIsAgent = useMemberAgentResolver(channel.id);
+
+  // Prompt cards and member join/leave rows share one chronological flow;
+  // membership rows are narration only — ↑/↓ card navigation skips them.
+  const items = React.useMemo(() => {
+    const merged: Array<
+      | { type: "prompt"; root: RelayEvent }
+      | { type: "membership"; change: MembershipChange }
+    > = [
+      ...roots.map((root) => ({
+        type: "prompt" as const,
+        root,
+      })),
+      ...memberships.map((change) => ({
+        type: "membership" as const,
+        change,
+      })),
+    ];
+    return merged.sort((left, right) =>
+      byCreatedAscending(
+        left.type === "prompt" ? left.root : left.change.event,
+        right.type === "prompt" ? right.root : right.change.event,
+      ),
+    );
+  }, [memberships, roots]);
+
+  const threadSummaries = React.useMemo(
+    () =>
+      windowQuery.data
+        ? channelWindowThreadSummaries(windowQuery.data)
+        : new Map<string, ChannelWindowThreadSummary>(),
+    [windowQuery.data],
+  );
+
+  const replyCounts = React.useMemo(() => {
+    const counts = new Map<string, number>();
+    for (const [rootId, summary] of threadSummaries) {
+      counts.set(rootId, summary.replyCount);
+    }
+    return counts;
+  }, [threadSummaries]);
+
+  // Threads with replies past the read frontier — carries the per-card
+  // unread dot. readStateVersion invalidates when any read marker moves.
+  // biome-ignore lint/correctness/useExhaustiveDependencies: readStateVersion is an intentional invalidation signal
+  const unreadRootIds = React.useMemo(
+    () =>
+      selectUnreadThreadRoots(threadSummaries, (rootId) =>
+        getThreadReadAt(rootId, channel.id),
+      ),
+    [channel.id, getThreadReadAt, threadSummaries, readStateVersion],
+  );
+
+  // Kind-7 reactions ride along as window aux events (pages + live); agents
+  // react while working, so these double as a per-prompt activity signal.
+  const rootReactions = React.useMemo(() => {
+    const store = windowQuery.data;
+    if (!store) return new Map<string, MessageReaction[]>();
+    return collectReactions([
+      ...store.pages.flatMap((page) => page.aux),
+      ...store.liveAux,
+    ]);
+  }, [windowQuery.data]);
+
+  return (
+    <div
+      ref={scrollRef}
+      className="min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-4 py-3 font-mono"
+      data-allow-text-selection
+      data-testid="dev-mode-transcript"
+      onScroll={handleScroll}
+    >
+      <div ref={contentRef}>
+        {items.map((item) =>
+          item.type === "membership" ? (
+            <MembershipRow
+              key={item.change.event.id}
+              change={item.change}
+              resolveColor={resolveColor}
+              resolveName={resolveName}
+            />
+          ) : (
+            <PromptCard
+              key={item.root.localKey ?? item.root.id}
+              channel={channel}
+              currentPubkey={currentPubkey}
+              markRead={markRead}
+              onOpenThread={() => onOpenThread(item.root.id)}
+              replyCount={replyCounts.get(item.root.id) ?? 0}
+              unread={unreadRootIds.has(item.root.id)}
+              resolveColor={resolveColor}
+              resolveIsAgent={resolveIsAgent}
+              resolveName={resolveName}
+              root={item.root}
+              rootReactions={rootReactions.get(item.root.id)}
+              selected={item.root.id === selectedRootId}
+            />
+          ),
+        )}
+        {messagesQuery.isLoading && roots.length === 0 ? (
+          <div className="text-sm text-muted-foreground/60">loading…</div>
+        ) : null}
+        {messagesQuery.isError ? (
+          <button
+            className="cursor-pointer py-0.5 text-sm text-destructive hover:underline"
+            onClick={() => void messagesQuery.refetch()}
+            type="button"
+          >
+            failed to load messages — retry
+          </button>
+        ) : null}
+      </div>
+    </div>
+  );
+}
diff --git a/desktop/src/features/settings/ui/SettingsPanels.tsx b/desktop/src/features/settings/ui/SettingsPanels.tsx
index e74d1f3837..18dd52c1e9 100644
--- a/desktop/src/features/settings/ui/SettingsPanels.tsx
+++ b/desktop/src/features/settings/ui/SettingsPanels.tsx
@@ -19,6 +19,7 @@ import {
   Smile,
   Sun,
   SunMoon,
+  Terminal,
   Ticket,
   UserRound,
   type LucideIcon,
@@ -36,6 +37,10 @@ import {
   useThreadViewMode,
   type ThreadViewMode,
 } from "@/features/channels/lib/threadViewModePreference";
+import {
+  setDisplayStyle,
+  useDisplayStyle,
+} from "@/features/dev-mode/lib/displayStylePreference";
 import { cn } from "@/shared/lib/cn";
 import { Button } from "@/shared/ui/button";
 import {
@@ -419,6 +424,7 @@ function ThemeSettingsCard() {
     followSystem,
     setFollowSystem,
   } = useTheme();
+  const displayStyle = useDisplayStyle();
 
   // Buzz themes pin a neutral accent (GitHub black in light, white in dark),
   // so the accent picker is hidden while a Buzz theme is active. `themeName` is
@@ -520,6 +526,41 @@ function ThemeSettingsCard() {
         description="Choose a theme for Buzz."
       />
 
+      {/* Display style: Standard / Developer */}
+      <div className="mb-4 flex gap-2">
+        {(
+          [
+            {
+              style: "standard" as const,
+              label: "Standard",
+              Icon: MessagesSquare,
+            },
+            {
+              style: "developer" as const,
+              label: "Developer",
+              Icon: Terminal,
+            },
+          ] as const
+        ).map(({ style, label, Icon }) => (
+          <button
+            aria-pressed={displayStyle === style}
+            className={cn(
+              "flex items-center gap-2 rounded-lg border px-4 py-2 text-sm font-medium transition-colors focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-ring",
+              displayStyle === style
+                ? "border-primary bg-primary/10 text-foreground"
+                : "border-border/70 text-muted-foreground hover:border-border hover:text-foreground",
+            )}
+            data-testid={`display-style-${style}`}
+            key={style}
+            onClick={() => setDisplayStyle(style)}
+            type="button"
+          >
+            <Icon className="h-4 w-4" />
+            {label}
+          </button>
+        ))}
+      </div>
+
       {/* Mode selector: System / Light / Dark */}
       <div className="mb-4 flex gap-2">
         {(
diff --git a/desktop/src/features/sidebar/ui/CommunityRail.tsx b/desktop/src/features/sidebar/ui/CommunityRail.tsx
index 386ee20691..e852111267 100644
--- a/desktop/src/features/sidebar/ui/CommunityRail.tsx
+++ b/desktop/src/features/sidebar/ui/CommunityRail.tsx
@@ -39,6 +39,8 @@ import { cn } from "@/shared/lib/cn";
 import { getInitials } from "@/shared/lib/initials";
 import { writeTextToClipboard } from "@/shared/lib/clipboard";
 
+type CommunityRailVariant = "standard" | "developer";
+
 type CommunityRailProps = {
   communities: Community[];
   activeCommunityId: string | null;
@@ -50,6 +52,8 @@ type CommunityRailProps = {
   ) => void;
   onRemoveCommunity: (id: string) => void;
   onReorderCommunities: (orderedIds: string[]) => void;
+  /** Developer mode swaps the round Discord-style tiles for flat squares. */
+  variant?: CommunityRailVariant;
 };
 
 const MAX_BADGE = 99;
@@ -96,6 +100,7 @@ function CommunityButton({
   dragListeners,
   dragAttributes,
   isDragging,
+  variant = "standard",
 }: {
   community: Community;
   isActive: boolean;
@@ -106,6 +111,7 @@ function CommunityButton({
   dragListeners?: React.HTMLAttributes<HTMLElement>;
   dragAttributes?: React.HTMLAttributes<HTMLElement>;
   isDragging?: boolean;
+  variant?: CommunityRailVariant;
 }) {
   const { mentionCount, showBadge, showDot, pending, badgeLabel } =
     communityRailIndicators(unread);
@@ -136,10 +142,20 @@ function CommunityButton({
             >
               <span
                 className={cn(
-                  "flex h-9 w-9 items-center justify-center overflow-hidden rounded-2xl text-xs font-semibold transition-all",
-                  isActive
-                    ? "rounded-xl bg-primary text-primary-foreground"
-                    : "bg-sidebar-accent/60 text-sidebar-foreground/80 hover:rounded-xl hover:bg-primary/80 hover:text-primary-foreground",
+                  "flex h-9 w-9 items-center justify-center overflow-hidden text-xs font-semibold",
+                  variant === "developer"
+                    ? cn(
+                        "rounded-none border font-mono",
+                        isActive
+                          ? "border-primary bg-primary/15 text-foreground"
+                          : "border-border/60 text-muted-foreground hover:border-primary/60 hover:text-foreground",
+                      )
+                    : cn(
+                        "rounded-2xl transition-all",
+                        isActive
+                          ? "rounded-xl bg-primary text-primary-foreground"
+                          : "bg-sidebar-accent/60 text-sidebar-foreground/80 hover:rounded-xl hover:bg-primary/80 hover:text-primary-foreground",
+                      ),
                   pending && !isActive && "opacity-60",
                 )}
               >
@@ -157,14 +173,24 @@ function CommunityButton({
               </span>
               {showBadge ? (
                 <span
-                  className="absolute -bottom-0.5 -right-0.5 flex h-4 min-w-4 items-center justify-center rounded-full bg-primary px-1 text-2xs font-semibold text-primary-foreground ring-2 ring-sidebar"
+                  className={cn(
+                    "absolute -bottom-0.5 -right-0.5 flex h-4 min-w-4 items-center justify-center bg-primary px-1 text-2xs font-semibold text-primary-foreground ring-2",
+                    variant === "developer"
+                      ? "rounded-none font-mono ring-background"
+                      : "rounded-full ring-sidebar",
+                  )}
                   data-testid={`community-rail-mentions-${community.id}`}
                 >
                   {badgeLabel}
                 </span>
               ) : showDot ? (
                 <span
-                  className="absolute -bottom-0.5 -right-0.5 h-2 w-2 shrink-0 rounded-full bg-primary ring-2 ring-sidebar"
+                  className={cn(
+                    "absolute -bottom-0.5 -right-0.5 h-2 w-2 shrink-0 bg-primary ring-2",
+                    variant === "developer"
+                      ? "rounded-none ring-background"
+                      : "rounded-full ring-sidebar",
+                  )}
                   data-testid={`community-rail-unread-dot-${community.id}`}
                 >
                   <span className="sr-only">unread</span>
@@ -185,13 +211,18 @@ function CommunityButton({
 function CommunityDragOverlay({
   community,
   iconUrl,
+  variant = "standard",
 }: {
   community: Community;
   iconUrl: string | null;
+  variant?: CommunityRailVariant;
 }) {
   return (
     <div
-      className="flex h-9 w-9 cursor-grabbing items-center justify-center overflow-hidden rounded-xl bg-primary text-xs font-semibold text-primary-foreground opacity-90 shadow-lg ring-1 ring-sidebar-border"
+      className={cn(
+        "flex h-9 w-9 cursor-grabbing items-center justify-center overflow-hidden bg-primary text-xs font-semibold text-primary-foreground opacity-90 shadow-lg ring-1 ring-sidebar-border",
+        variant === "developer" ? "rounded-none font-mono" : "rounded-xl",
+      )}
       data-buzz-flat
     >
       {iconUrl ? (
@@ -218,6 +249,7 @@ function SortableCommunityButton({
   onSwitchCommunity,
   onMarkAllRead,
   onSetEditingCommunity,
+  variant = "standard",
 }: {
   community: Community;
   activeCommunityId: string | null;
@@ -228,6 +260,7 @@ function SortableCommunityButton({
   onSwitchCommunity: (id: string) => void;
   onMarkAllRead: (community: Community) => void;
   onSetEditingCommunity: (community: Community) => void;
+  variant?: CommunityRailVariant;
 }) {
   const {
     attributes,
@@ -286,6 +319,7 @@ function SortableCommunityButton({
             state: "unknown",
           }
         }
+        variant={variant}
       />
     </div>
   );
@@ -307,6 +341,7 @@ export function CommunityRail({
   onUpdateCommunity,
   onRemoveCommunity,
   onReorderCommunities,
+  variant = "standard",
 }: CommunityRailProps) {
   const { unreadByCommunity, markCommunityRead } = useCommunityUnread(
     communities,
@@ -370,7 +405,12 @@ export function CommunityRail({
   return (
     <nav
       aria-label="Communities"
-      className="relative z-20 flex w-14 shrink-0 flex-col items-center gap-2 overflow-y-auto bg-sidebar px-2.5 pb-5 pt-[calc(var(--buzz-top-chrome-height,40px)+7px)]"
+      className={cn(
+        "relative z-20 flex w-14 shrink-0 flex-col items-center gap-2 overflow-y-auto px-2.5 pb-5 pt-[calc(var(--buzz-top-chrome-height,40px)+7px)]",
+        variant === "developer"
+          ? "border-r border-border/60 bg-background font-mono"
+          : "bg-sidebar",
+      )}
       data-testid="community-rail"
     >
       <DndContext
@@ -396,6 +436,7 @@ export function CommunityRail({
               onMarkAllRead={handleMarkAllRead}
               onSetEditingCommunity={setEditingCommunity}
               onSwitchCommunity={onSwitchCommunity}
+              variant={variant}
             />
           ))}
         </SortableContext>
@@ -404,6 +445,7 @@ export function CommunityRail({
             <CommunityDragOverlay
               community={draggingCommunity}
               iconUrl={iconsByCommunity[draggingCommunity.id] ?? null}
+              variant={variant}
             />
           ) : null}
         </DragOverlay>
@@ -412,7 +454,12 @@ export function CommunityRail({
         <TooltipTrigger asChild>
           <button
             aria-label="Add community"
-            className="flex h-9 w-9 items-center justify-center rounded-2xl bg-sidebar-accent/60 text-sidebar-foreground/70 outline-hidden transition-all hover:rounded-xl hover:bg-primary/80 hover:text-primary-foreground focus:outline-none focus-visible:outline-none"
+            className={cn(
+              "flex h-9 w-9 items-center justify-center outline-hidden focus:outline-none focus-visible:outline-none",
+              variant === "developer"
+                ? "rounded-none border border-dashed border-border/60 text-muted-foreground hover:border-primary/60 hover:text-foreground"
+                : "rounded-2xl bg-sidebar-accent/60 text-sidebar-foreground/70 transition-all hover:rounded-xl hover:bg-primary/80 hover:text-primary-foreground",
+            )}
             data-testid="community-rail-add"
             onClick={onAddCommunity}
             type="button"
diff --git a/desktop/src/main.tsx b/desktop/src/main.tsx
index 890ef72226..ecb5a900e9 100644
--- a/desktop/src/main.tsx
+++ b/desktop/src/main.tsx
@@ -3,6 +3,7 @@ import ReactDOM from "react-dom/client";
 import { App } from "@/app/App";
 import { NostrBindConsentDialog } from "@/features/profile/ui/NostrBindConsentDialog";
 import "@fontsource-variable/inter/wght.css";
+import "@fontsource-variable/jetbrains-mono/wght.css";
 import "@/shared/styles/globals.css";
 import { UpdaterProvider } from "@/features/settings/hooks/UpdaterProvider";
 import { migrateLegacyCommunityStorageBeforeRender } from "@/features/communities/legacyCommunityStorage";
diff --git a/desktop/src/shared/api/agentCompletion.ts b/desktop/src/shared/api/agentCompletion.ts
new file mode 100644
index 0000000000..992ed889b8
--- /dev/null
+++ b/desktop/src/shared/api/agentCompletion.ts
@@ -0,0 +1,25 @@
+import { invokeTauri } from "@/shared/api/tauri";
+
+export type GenerateAgentCompletionInput = {
+  /** Managed agent pubkey whose configured harness runs the prompt. */
+  pubkey: string;
+  prompt: string;
+  systemPrompt?: string;
+};
+
+/**
+ * Run one bounded prompt through a managed agent and return its reply text.
+ *
+ * Spawns a short-lived agent subprocess — no relay traffic, nothing appears
+ * in any channel. Slow (agent startup + one turn); callers must not block
+ * interactive flows on it.
+ */
+export async function generateAgentCompletion(
+  input: GenerateAgentCompletionInput,
+): Promise<string> {
+  return invokeTauri<string>("generate_agent_completion", {
+    pubkey: input.pubkey,
+    prompt: input.prompt,
+    systemPrompt: input.systemPrompt ?? null,
+  });
+}
diff --git a/desktop/src/testing/e2eBridge.ts b/desktop/src/testing/e2eBridge.ts
index 4cfc553df1..bdd3568730 100644
--- a/desktop/src/testing/e2eBridge.ts
+++ b/desktop/src/testing/e2eBridge.ts
@@ -281,6 +281,9 @@ type E2eConfig = {
     profileUpdateErrors?: string[];
     searchProfiles?: MockSearchProfileSeed[];
     updateAvailable?: boolean;
+    /** Delay (ms) before mock `archive_channel` resolves, to test that the
+     *  UI updates optimistically without waiting on the relay. */
+    archiveChannelDelayMs?: number;
     updateChannelDelayMs?: number;
     updateDownloadDelayMs?: number;
     restartDelayMs?: number;
@@ -1021,6 +1024,13 @@ declare global {
       /** 64-hex id required for the event to be a valid reaction target. */
       id?: string;
     }) => RelayEvent;
+    /** Bulk-add `count` synthetic members to a mock channel so specs can
+     *  exercise large-roster UI (member counts, capped browsers) without
+     *  seeding hundreds of identities. Returns the new member total. */
+    __BUZZ_E2E_ADD_MOCK_MEMBERS__?: (input: {
+      channelName: string;
+      count: number;
+    }) => number;
     /** Prepend `count` synthetic older messages to a channel's mock store so
      *  an older-history fetch has something to paginate. Mirrors how the real
      *  relay backfills history. Returns the created events. */
@@ -6326,6 +6336,11 @@ async function handleArchiveChannel(
   args: { channelId: string },
   config: E2eConfig | undefined,
 ) {
+  const delayMs = config?.mock?.archiveChannelDelayMs ?? 0;
+  if (delayMs > 0) {
+    await new Promise((resolve) => window.setTimeout(resolve, delayMs));
+  }
+
   const identity = getIdentity(config);
   if (!identity) {
     const channel = getMockChannel(args.channelId);
@@ -9437,6 +9452,28 @@ export function maybeInstallE2eTauriMocks() {
       id,
     );
   };
+  window.__BUZZ_E2E_ADD_MOCK_MEMBERS__ = ({ channelName, count }) => {
+    const channel = mockChannels.find(
+      (candidate) => candidate.name === channelName,
+    );
+    if (!channel) {
+      throw new Error(`Mock channel ${channelName} not found.`);
+    }
+
+    const base = channel.members.length;
+    for (let index = 0; index < count; index += 1) {
+      const serial = (base + index).toString(16).padStart(12, "0");
+      channel.members.push({
+        pubkey: `e2ec${serial}`.padEnd(64, "0"),
+        role: "member",
+        is_agent: false,
+        joined_at: new Date().toISOString(),
+        display_name: `crowd-${base + index}`,
+      });
+    }
+    syncMockChannel(channel);
+    return channel.members.length;
+  };
   window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ = prependMockHistory;
   window.__BUZZ_E2E_EMIT_MOCK_TYPING__ = ({
     channelName,
diff --git a/desktop/tailwind.config.js b/desktop/tailwind.config.js
index 8905fc16ce..f0a2ebe40c 100644
--- a/desktop/tailwind.config.js
+++ b/desktop/tailwind.config.js
@@ -45,6 +45,14 @@ export default {
           '"Segoe UI"',
           "sans-serif",
         ],
+        mono: [
+          '"JetBrains Mono Variable"',
+          '"JetBrains Mono"',
+          "ui-monospace",
+          "SFMono-Regular",
+          "Menlo",
+          "monospace",
+        ],
       },
       colors: {
         background: "hsl(var(--background))",
diff --git a/desktop/tests/e2e/community-rail.spec.ts b/desktop/tests/e2e/community-rail.spec.ts
index 0c78108190..0070fdb28c 100644
--- a/desktop/tests/e2e/community-rail.spec.ts
+++ b/desktop/tests/e2e/community-rail.spec.ts
@@ -69,6 +69,34 @@ test.describe("community rail", () => {
     await expect(page.getByTestId("community-rail-add")).toBeVisible();
   });
 
+  test("renders the flat developer variant in developer mode", async ({
+    page,
+  }) => {
+    await installMockBridge(page, undefined, { skipCommunitySeed: true });
+    await seedCommunities(page, [COMMUNITY_A, COMMUNITY_B], COMMUNITY_A.id);
+    await page.addInitScript(() => {
+      localStorage.setItem("buzz.displayStyle", "developer");
+    });
+    await page.goto("/");
+
+    await page.getByTestId("dev-mode-composer").waitFor();
+    const rail = page.getByTestId("community-rail");
+    await expect(rail).toBeVisible();
+
+    // Developer mode squares off the tiles; standard mode rounds them.
+    const tile = page
+      .getByTestId(`community-rail-button-${COMMUNITY_A.id}`)
+      .locator(":scope > span")
+      .first();
+    await expect(tile).toHaveCSS("border-top-left-radius", "0px");
+
+    // Switching still works from the developer rail.
+    await page.getByTestId(`community-rail-button-${COMMUNITY_B.id}`).click();
+    await expect(
+      page.getByTestId(`community-rail-button-${COMMUNITY_B.id}`),
+    ).toHaveAttribute("aria-current", "true");
+  });
+
   test("restores pointer events after dismissing community settings", async ({
     page,
   }) => {
diff --git a/desktop/tests/e2e/dev-mode-composer-default.spec.ts b/desktop/tests/e2e/dev-mode-composer-default.spec.ts
new file mode 100644
index 0000000000..d92e2f30e7
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-composer-default.spec.ts
@@ -0,0 +1,73 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge } from "../helpers/bridge";
+
+// The fresh composer must target the default agent — the first managed
+// (local) agent — rather than plain chat. Tab still cycles through every
+// mode, including chat.
+
+test("fresh composer defaults to an agent target, not chat", async ({
+  page,
+}) => {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+
+  // Mock managed agents (Fizz/Honey/Bumble) load async; the mode line must
+  // settle on "to <agent>" without any Tab press.
+  const modeLine = page.getByTestId("dev-mode-pill").first();
+  await expect(modeLine).toContainText(/^to /);
+  await expect(modeLine).not.toHaveText("chat");
+
+  // Tab cycling still reaches chat mode and comes back around.
+  await composer.focus();
+  const initial = await modeLine.innerText();
+  let sawChat = false;
+  for (let step = 0; step < 12; step += 1) {
+    await page.keyboard.press("Tab");
+    const label = (await modeLine.innerText()).trim();
+    if (label === "chat") sawChat = true;
+    if (sawChat && label === initial.trim()) break;
+  }
+  expect(sawChat).toBe(true);
+  await expect(modeLine).toHaveText(initial);
+});
+
+test("composer remembers the last Tab-cycled target across reloads", async ({
+  page,
+}) => {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+
+  const modeLine = page.getByTestId("dev-mode-pill").first();
+  await expect(modeLine).toContainText(/^to /);
+  const initial = (await modeLine.innerText()).trim();
+
+  // Cycle to a different agent target (skipping plain chat).
+  await composer.focus();
+  let cycled = "";
+  for (let step = 0; step < 12; step += 1) {
+    await page.keyboard.press("Tab");
+    const label = (await modeLine.innerText()).trim();
+    if (label !== "chat" && label !== initial) {
+      cycled = label;
+      break;
+    }
+  }
+  expect(cycled).not.toBe("");
+
+  await page.reload({ waitUntil: "domcontentloaded" });
+  await page.getByTestId("dev-mode-composer").waitFor();
+  await expect(page.getByTestId("dev-mode-pill").first()).toHaveText(cycled);
+});
diff --git a/desktop/tests/e2e/dev-mode-first-reply.spec.ts b/desktop/tests/e2e/dev-mode-first-reply.spec.ts
new file mode 100644
index 0000000000..d0a30ea2b8
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-first-reply.spec.ts
@@ -0,0 +1,227 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge, TEST_IDENTITIES } from "../helpers/bridge";
+
+// Every prompt card in the developer-mode transcript shows the agent's first
+// response inline — regardless of how old the prompt is — while any later
+// side-chat messages stay collapsed behind a "… N more replies" affordance
+// that opens the thread pane.
+
+test("dev mode shows the first thread reply inline and collapses the rest", async ({
+  page,
+}) => {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+
+  const channelName = "general";
+  const rootText = "prompt: investigate the flaky deploy";
+  const firstReplyText = "agent first response: found the flaky step";
+  const laterReplyText = "side chat follow-up: can you elaborate?";
+  const thirdReplyText = "agent elaboration: it is the cache key";
+
+  // Seed a root prompt plus a thread under it before the channel window is
+  // fetched, so the snapshot carries the 39005 summary for the root.
+  await page.evaluate(
+    ({
+      channel,
+      agent,
+      rootText,
+      firstReplyText,
+      laterReplyText,
+      thirdReplyText,
+    }) => {
+      const emit = window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__;
+      if (!emit) throw new Error("mock bridge missing");
+      const now = Math.floor(Date.now() / 1000);
+      const root = emit({
+        channelName: channel,
+        content: rootText,
+        createdAt: now - 40,
+      });
+      emit({
+        channelName: channel,
+        content: firstReplyText,
+        parentEventId: root.id,
+        pubkey: agent,
+        createdAt: now - 30,
+      });
+      emit({
+        channelName: channel,
+        content: laterReplyText,
+        parentEventId: root.id,
+        createdAt: now - 20,
+      });
+      emit({
+        channelName: channel,
+        content: thirdReplyText,
+        parentEventId: root.id,
+        pubkey: agent,
+        createdAt: now - 10,
+      });
+    },
+    {
+      channel: channelName,
+      agent: TEST_IDENTITIES.bob.pubkey,
+      rootText,
+      firstReplyText,
+      laterReplyText,
+      thirdReplyText,
+    },
+  );
+
+  // ArrowUp steps through channel previews newest-first; walk until the
+  // seeded channel is previewed, then Enter opens it.
+  await composer.focus();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  for (let step = 0; step < 20; step += 1) {
+    await page.keyboard.press("ArrowUp");
+    const previewed = (await topBar.innerText()).replace(/^#\s*/, "").trim();
+    if (previewed === channelName) break;
+  }
+  await expect(topBar).toContainText(channelName);
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+
+  const card = page
+    .getByTestId("dev-mode-prompt-card")
+    .filter({ hasText: rootText });
+  await expect(card).toBeVisible();
+
+  // The first reply renders inline; later thread messages do not.
+  await expect(card).toContainText(firstReplyText);
+  await expect(card).not.toContainText(laterReplyText);
+  await expect(card).not.toContainText(thirdReplyText);
+
+  // The collapsed indicator counts only the messages after the first reply
+  // and never labels the first response itself as a hidden reply.
+  const more = card.getByTestId("dev-mode-more-replies");
+  await expect(more).toHaveText(/…\s*2 more replies/);
+
+  // Opening the thread shows the complete conversation in the side pane.
+  await more.click();
+  const threadPanel = page.getByTestId("dev-mode-thread-panel");
+  await expect(threadPanel).toBeVisible();
+  await expect(threadPanel).toContainText(firstReplyText);
+  await expect(threadPanel).toContainText(laterReplyText);
+  await expect(threadPanel).toContainText(thirdReplyText);
+});
+
+// The whole leading run of agent replies renders inline — collapsing only
+// starts once a human responds in the thread.
+test("dev mode shows all agent replies inline until a human responds", async ({
+  page,
+}) => {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+
+  // The seeded "agents" channel has charlie as a bot member, so his
+  // replies resolve as agent-authored.
+  const channelName = "agents";
+  const rootText = "prompt: roll out the fix everywhere";
+  const agentReply1 = "agent: on it, tracking the rollout";
+  const agentReply2 = "agent: fleet is on the fixed build, verifying";
+  const humanReply = "human: thanks, looks good so far";
+  const agentReply3 = "agent: confirmed fixed on all hosts";
+
+  await page.evaluate(
+    ({
+      channel,
+      agent,
+      rootText,
+      agentReply1,
+      agentReply2,
+      humanReply,
+      agentReply3,
+    }) => {
+      const emit = window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__;
+      if (!emit) throw new Error("mock bridge missing");
+      const now = Math.floor(Date.now() / 1000);
+      const root = emit({
+        channelName: channel,
+        content: rootText,
+        createdAt: now - 50,
+      });
+      emit({
+        channelName: channel,
+        content: agentReply1,
+        parentEventId: root.id,
+        pubkey: agent,
+        createdAt: now - 40,
+      });
+      emit({
+        channelName: channel,
+        content: agentReply2,
+        parentEventId: root.id,
+        pubkey: agent,
+        createdAt: now - 30,
+      });
+      emit({
+        channelName: channel,
+        content: humanReply,
+        parentEventId: root.id,
+        createdAt: now - 20,
+      });
+      emit({
+        channelName: channel,
+        content: agentReply3,
+        parentEventId: root.id,
+        pubkey: agent,
+        createdAt: now - 10,
+      });
+    },
+    {
+      channel: channelName,
+      agent: TEST_IDENTITIES.charlie.pubkey,
+      rootText,
+      agentReply1,
+      agentReply2,
+      humanReply,
+      agentReply3,
+    },
+  );
+
+  await composer.focus();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  for (let step = 0; step < 20; step += 1) {
+    await page.keyboard.press("ArrowUp");
+    const previewed = (await topBar.innerText()).replace(/^#\s*/, "").trim();
+    if (previewed === channelName) break;
+  }
+  await expect(topBar).toContainText(channelName);
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+
+  const card = page
+    .getByTestId("dev-mode-prompt-card")
+    .filter({ hasText: rootText });
+  await expect(card).toBeVisible();
+
+  // Both leading agent replies render inline; the human reply and the
+  // agent reply after it stay collapsed.
+  await expect(card).toContainText(agentReply1);
+  await expect(card).toContainText(agentReply2);
+  await expect(card).not.toContainText(humanReply);
+  await expect(card).not.toContainText(agentReply3);
+
+  const more = card.getByTestId("dev-mode-more-replies");
+  await expect(more).toHaveText(/…\s*2 more replies/);
+
+  // The side chat still shows the complete conversation.
+  await more.click();
+  const threadPanel = page.getByTestId("dev-mode-thread-panel");
+  await expect(threadPanel).toBeVisible();
+  await expect(threadPanel).toContainText(humanReply);
+  await expect(threadPanel).toContainText(agentReply3);
+});
diff --git a/desktop/tests/e2e/dev-mode-media.spec.ts b/desktop/tests/e2e/dev-mode-media.spec.ts
new file mode 100644
index 0000000000..5342c576ab
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-media.spec.ts
@@ -0,0 +1,202 @@
+import { expect, type Page, test } from "@playwright/test";
+
+import { installMockBridge } from "../helpers/bridge";
+
+// Developer mode must support the full attachment flow: paste an image or
+// video into either composer (main channel or side chat), see the pending
+// chip, send, and get an interactive media block in the transcript — the
+// same lightbox/video-player path the standard renderer uses.
+
+const IMAGE_SHA = "a".repeat(64);
+const IMAGE_URL = `http://localhost:3000/media/${IMAGE_SHA}.png`;
+const IMAGE_DESCRIPTOR = {
+  url: IMAGE_URL,
+  sha256: IMAGE_SHA,
+  size: 4096,
+  type: "image/png",
+  uploaded: 1_700_000_000,
+  dim: "64x64",
+  filename: "screenshot.png",
+};
+
+const VIDEO_SHA = "b".repeat(64);
+const VIDEO_URL = `http://localhost:3000/media/${VIDEO_SHA}.mp4`;
+const VIDEO_DESCRIPTOR = {
+  url: VIDEO_URL,
+  sha256: VIDEO_SHA,
+  size: 8192,
+  type: "video/mp4",
+  uploaded: 1_700_000_000,
+  filename: "clip.mp4",
+};
+
+/** Dispatch a real ClipboardEvent carrying a File — Playwright's
+ * dispatchEvent falls back to a bare Event for "paste", which drops
+ * clipboardData, so the event must be constructed in the page. */
+async function pasteFile(
+  page: Page,
+  testId: string,
+  filename: string,
+  mime: string,
+) {
+  await page.evaluate(
+    ({ testId, filename, mime }) => {
+      const target = document.querySelector(`[data-testid="${testId}"]`);
+      if (!target) throw new Error(`missing ${testId}`);
+      const transfer = new DataTransfer();
+      transfer.items.add(
+        new File([new Uint8Array([137, 80, 78, 71])], filename, {
+          type: mime,
+        }),
+      );
+      target.dispatchEvent(
+        new ClipboardEvent("paste", {
+          bubbles: true,
+          cancelable: true,
+          clipboardData: transfer,
+        }),
+      );
+    },
+    { testId, filename, mime },
+  );
+}
+
+async function openDevModeChannel(page: Page) {
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+  await composer.focus();
+  await page.keyboard.press("ArrowUp");
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+  return composer;
+}
+
+test.beforeEach(async ({ page }) => {
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+});
+
+test("pasted image attaches, is removable, and renders interactively", async ({
+  page,
+}) => {
+  await installMockBridge(page, { uploadDescriptors: [IMAGE_DESCRIPTOR] });
+  const composer = await openDevModeChannel(page);
+
+  // Paste → pending chip with the filename.
+  await pasteFile(page, "dev-mode-composer", "screenshot.png", "image/png");
+  const chip = page.getByTestId("dev-mode-attachment-chip");
+  await expect(chip).toBeVisible();
+  await expect(chip).toContainText("screenshot.png");
+
+  // Remove → chip disappears; nothing is sent.
+  await chip.getByRole("button", { name: "remove attachment" }).click();
+  await expect(chip).toHaveCount(0);
+
+  // Paste again and send with text.
+  await pasteFile(page, "dev-mode-composer", "screenshot.png", "image/png");
+  await expect(page.getByTestId("dev-mode-attachment-chip")).toBeVisible();
+  await composer.fill("here is a screenshot");
+  await page.keyboard.press("Enter");
+
+  // Chip clears and the transcript shows the standard interactive image
+  // block (lightbox trigger), not a raw markdown line.
+  await expect(page.getByTestId("dev-mode-attachment-chip")).toHaveCount(0);
+  const transcript = page.getByTestId("dev-mode-transcript");
+  await expect(
+    transcript.getByText("here is a screenshot", { exact: false }),
+  ).toBeVisible();
+  await expect(
+    transcript.getByTestId("message-image-lightbox-trigger"),
+  ).toBeVisible();
+  await expect(transcript).not.toContainText(`![image](${IMAGE_URL})`);
+
+  // Media must not push the pane wider than its box.
+  const widths = await transcript.evaluate((el) => ({
+    scrollWidth: el.scrollWidth,
+    clientWidth: el.clientWidth,
+  }));
+  expect(widths.scrollWidth).toBeLessThanOrEqual(widths.clientWidth + 1);
+});
+
+test("attachment-only send posts the image to the channel", async ({
+  page,
+}) => {
+  await installMockBridge(page, { uploadDescriptors: [IMAGE_DESCRIPTOR] });
+  await openDevModeChannel(page);
+
+  await pasteFile(page, "dev-mode-composer", "screenshot.png", "image/png");
+  await expect(page.getByTestId("dev-mode-attachment-chip")).toBeVisible();
+  await page.keyboard.press("Enter");
+
+  await expect(page.getByTestId("dev-mode-attachment-chip")).toHaveCount(0);
+  await expect(
+    page
+      .getByTestId("dev-mode-transcript")
+      .getByTestId("message-image-lightbox-trigger"),
+  ).toBeVisible();
+});
+
+test("enter during an in-flight upload does not send without the attachment", async ({
+  page,
+}) => {
+  await installMockBridge(page, {
+    uploadDescriptors: [IMAGE_DESCRIPTOR],
+    uploadDelayMs: 1_500,
+  });
+  const composer = await openDevModeChannel(page);
+
+  await pasteFile(page, "dev-mode-composer", "screenshot.png", "image/png");
+  await expect(page.getByTestId("dev-mode-attachment-uploading")).toBeVisible();
+  await composer.fill("wait for the upload");
+  await page.keyboard.press("Enter");
+
+  // The send is held: the input keeps its text while the upload runs.
+  await expect(composer).toHaveValue("wait for the upload");
+
+  // Once the upload settles into a chip, Enter sends text + image together.
+  await expect(page.getByTestId("dev-mode-attachment-chip")).toBeVisible();
+  await page.keyboard.press("Enter");
+  const transcript = page.getByTestId("dev-mode-transcript");
+  await expect(
+    transcript.getByText("wait for the upload", { exact: false }),
+  ).toBeVisible();
+  await expect(
+    transcript.getByTestId("message-image-lightbox-trigger"),
+  ).toBeVisible();
+});
+
+test("pasted video sends from the side chat and renders with controls", async ({
+  page,
+}) => {
+  await installMockBridge(page, { uploadDescriptors: [VIDEO_DESCRIPTOR] });
+  const composer = await openDevModeChannel(page);
+
+  // Post a prompt to create a card, then open its side chat.
+  await composer.fill("check the video flow");
+  await page.keyboard.press("Enter");
+  await expect(
+    page
+      .getByTestId("dev-mode-transcript")
+      .getByText("check the video flow", { exact: false }),
+  ).toBeVisible();
+  await page.keyboard.press("ArrowUp");
+  await page.keyboard.press("Enter");
+  const panel = page.getByTestId("dev-mode-thread-panel");
+  await panel.waitFor();
+
+  await pasteFile(page, "dev-mode-thread-composer", "clip.mp4", "video/mp4");
+  const chip = panel.getByTestId("dev-mode-attachment-chip");
+  await expect(chip).toBeVisible();
+  await expect(chip).toContainText("clip.mp4");
+
+  await page.getByTestId("dev-mode-thread-composer").fill("video attached");
+  await page.keyboard.press("Enter");
+
+  await expect(panel.getByTestId("dev-mode-attachment-chip")).toHaveCount(0);
+  await expect(
+    panel.getByText("video attached", { exact: false }),
+  ).toBeVisible();
+  await expect(panel.getByTestId("video-player")).toBeVisible();
+});
diff --git a/desktop/tests/e2e/dev-mode-members.spec.ts b/desktop/tests/e2e/dev-mode-members.spec.ts
new file mode 100644
index 0000000000..48613774fc
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-members.spec.ts
@@ -0,0 +1,157 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge, TEST_IDENTITIES } from "../helpers/bridge";
+
+// Developer mode must show who is in the chat: the top bar lists the
+// channel's members, and member join/leave system messages (kind:40099)
+// render as narration rows in the transcript.
+
+test("dev mode lists channel members and narrates joins/leaves", async ({
+  page,
+}) => {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+
+  // ArrowUp steps through channel previews newest-first; walk until the
+  // multi-member mock channel ("general": tyler, alice, bob, mira) is
+  // previewed, then Enter opens it.
+  await composer.focus();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  const channelName = "general";
+  for (let step = 0; step < 20; step += 1) {
+    await page.keyboard.press("ArrowUp");
+    const previewed = (await topBar.innerText()).replace(/^#\s*/, "").trim();
+    if (previewed === channelName) break;
+  }
+  await expect(topBar).toContainText(channelName);
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+
+  const members = page.getByTestId("dev-mode-channel-members");
+  await expect(members).toContainText("alice");
+  await expect(members).toContainText("bob");
+
+  await page.waitForFunction(
+    (name) =>
+      window.__BUZZ_E2E_HAS_MOCK_LIVE_SUBSCRIPTION__?.({
+        channelName: name,
+      }) ?? false,
+    channelName,
+  );
+
+  const membershipRows = page.getByTestId("dev-mode-membership-row");
+
+  await page.evaluate(
+    ({ channel, actor }) => {
+      window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
+        channelName: channel,
+        kind: 40099,
+        pubkey: actor,
+        content: JSON.stringify({ type: "member_left", actor }),
+      });
+    },
+    { channel: channelName, actor: TEST_IDENTITIES.bob.pubkey },
+  );
+  await expect(membershipRows.filter({ hasText: "bob left" })).toBeVisible();
+
+  await page.evaluate(
+    ({ channel, target }) => {
+      window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
+        channelName: channel,
+        kind: 40099,
+        pubkey: target,
+        content: JSON.stringify({
+          type: "member_joined",
+          actor: target,
+          target,
+        }),
+      });
+    },
+    { channel: channelName, target: TEST_IDENTITIES.bob.pubkey },
+  );
+  await expect(membershipRows.filter({ hasText: "bob joined" })).toBeVisible();
+});
+
+// Channels can have 1000+ members: the top bar must collapse to a count
+// instead of listing names, and the palette's member browser must stay
+// responsive by capping rendered rows until the query narrows the roster.
+test("dev mode collapses large member lists to a searchable count", async ({
+  page,
+}) => {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+
+  await composer.focus();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  const channelName = "general";
+  for (let step = 0; step < 20; step += 1) {
+    await page.keyboard.press("ArrowUp");
+    const previewed = (await topBar.innerText()).replace(/^#\s*/, "").trim();
+    if (previewed === channelName) break;
+  }
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+
+  // 4 seeded members render as names.
+  const members = page.getByTestId("dev-mode-channel-members");
+  await expect(members).toContainText("alice");
+
+  await page.waitForFunction(
+    (name) =>
+      window.__BUZZ_E2E_HAS_MOCK_LIVE_SUBSCRIPTION__?.({
+        channelName: name,
+      }) ?? false,
+    channelName,
+  );
+
+  // Grow the roster past the inline threshold, then emit a membership
+  // event — the same live path a real join takes — to refresh the queries.
+  await page.evaluate(
+    ({ channel, actor }) => {
+      window.__BUZZ_E2E_ADD_MOCK_MEMBERS__?.({
+        channelName: channel,
+        count: 200,
+      });
+      window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
+        channelName: channel,
+        kind: 40099,
+        pubkey: actor,
+        content: JSON.stringify({
+          type: "member_joined",
+          actor,
+          target: actor,
+        }),
+      });
+    },
+    { channel: channelName, actor: TEST_IDENTITIES.bob.pubkey },
+  );
+  await expect(members).toContainText("204 members");
+
+  // Clicking the count opens the palette's member browser: rendered rows
+  // are capped with an overflow hint, and typing narrows the roster.
+  await members.click();
+  const paletteInput = page.getByTestId("dev-mode-palette-input");
+  await expect(paletteInput).toHaveAttribute(
+    "placeholder",
+    /search members of # general/,
+  );
+  const entries = page.getByTestId("dev-mode-palette-entry");
+  await expect(entries).toHaveCount(41);
+  await expect(entries.last()).toContainText("more — type to narrow");
+
+  await paletteInput.fill("alice");
+  await expect(entries).toHaveCount(1);
+  await expect(entries.first()).toContainText("alice");
+});
diff --git a/desktop/tests/e2e/dev-mode-mentions.spec.ts b/desktop/tests/e2e/dev-mode-mentions.spec.ts
new file mode 100644
index 0000000000..88a101c472
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-mentions.spec.ts
@@ -0,0 +1,138 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge, TEST_IDENTITIES } from "../helpers/bridge";
+
+// Typing `@` in a developer-mode composer autocompletes users: channel
+// members rank first, relay-wide search fills in the rest. Accepting a
+// suggestion keeps the literal `@Display Name` in the text, and sending
+// emits a ["p", pubkey] tag for it. Mentioning a non-member best-effort
+// adds them to the channel before the send.
+
+async function openDevModeChannel(
+  page: import("@playwright/test").Page,
+  channelName: string,
+) {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+  await composer.focus();
+
+  // ArrowUp steps through channel previews newest-first; walk until the
+  // requested channel is previewed, then Enter opens it.
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  for (let step = 0; step < 20; step += 1) {
+    await page.keyboard.press("ArrowUp");
+    const previewed = (await topBar.innerText()).replace(/^#\s*/, "").trim();
+    if (previewed === channelName) break;
+  }
+  await expect(topBar).toContainText(channelName);
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+  return composer;
+}
+
+test("composer @-mention autocompletes a relay user into a p-tagged send", async ({
+  page,
+}) => {
+  // outsider exists on the relay but is not a member of #general.
+  const composer = await openDevModeChannel(page, "general");
+
+  await composer.pressSequentially("hey @out");
+  const suggestions = page.getByTestId("dev-mode-mention-suggestions");
+  await expect(suggestions).toBeVisible();
+  await expect(suggestions).toContainText("outsider");
+  await expect(suggestions).toContainText("adds to channel");
+
+  await page.keyboard.press("Tab");
+  await expect(suggestions).not.toBeVisible();
+  await expect(composer).toHaveValue(/@outsider /);
+
+  const marker = `please review ${Date.now()}`;
+  await composer.pressSequentially(marker);
+  await page.keyboard.press("Enter");
+
+  const transcript = page.getByTestId("dev-mode-transcript");
+  await expect(transcript).toContainText("@outsider");
+  await expect(transcript).toContainText(marker);
+
+  // The signed outgoing event carries the mention p tag.
+  await expect
+    .poll(() =>
+      page.evaluate((needle) => {
+        const events = (
+          window as Window & {
+            __BUZZ_E2E_SIGNED_EVENTS__?: Array<{
+              content: string;
+              tags: string[][];
+            }>;
+          }
+        ).__BUZZ_E2E_SIGNED_EVENTS__;
+        return (
+          events?.find((event) => event.content.includes(needle))?.tags ?? []
+        );
+      }, marker),
+    )
+    .toContainEqual(["p", TEST_IDENTITIES.outsider.pubkey]);
+
+  // Mentioning a non-member pulls them into the channel best-effort.
+  const commandLog = await page.evaluate(() => {
+    return (
+      (
+        window as Window & {
+          __BUZZ_E2E_COMMAND_LOG__?: Array<{
+            command: string;
+            payload: unknown;
+          }>;
+        }
+      ).__BUZZ_E2E_COMMAND_LOG__ ?? []
+    );
+  });
+  expect(commandLog).toEqual(
+    expect.arrayContaining([
+      expect.objectContaining({
+        command: "add_channel_members",
+        payload: expect.objectContaining({
+          pubkeys: expect.arrayContaining([TEST_IDENTITIES.outsider.pubkey]),
+        }),
+      }),
+    ]),
+  );
+});
+
+test("mid-word @ (email addresses) does not open mention autocomplete", async ({
+  page,
+}) => {
+  const composer = await openDevModeChannel(page, "general");
+
+  await composer.pressSequentially("reach me at joe@out");
+  await expect(
+    page.getByTestId("dev-mode-mention-suggestions"),
+  ).not.toBeVisible();
+});
+
+test("side-chat composer @-mention suggests channel members", async ({
+  page,
+}) => {
+  await openDevModeChannel(page, "general");
+
+  // ArrowUp selects the newest card; Enter opens its side chat.
+  await page.keyboard.press("ArrowUp");
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-thread-panel").waitFor();
+
+  const threadComposer = page.getByTestId("dev-mode-thread-composer");
+  await threadComposer.focus();
+  await threadComposer.pressSequentially("@ali");
+
+  const suggestions = page.getByTestId("dev-mode-mention-suggestions");
+  await expect(suggestions).toBeVisible();
+  await expect(suggestions).toContainText("alice");
+
+  await page.keyboard.press("Tab");
+  await expect(threadComposer).toHaveValue(/@alice /);
+});
diff --git a/desktop/tests/e2e/dev-mode-overflow.spec.ts b/desktop/tests/e2e/dev-mode-overflow.spec.ts
new file mode 100644
index 0000000000..54048fc50a
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-overflow.spec.ts
@@ -0,0 +1,83 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge } from "../helpers/bridge";
+
+// Developer-mode transcripts must keep chat content inside their pane: long
+// unbroken words wrap, link labels wrap, and nothing pushes the shell wider
+// than the window (the shell is a flex item — without min-w-0 its intrinsic
+// min-content width lets nowrap content blow the layout out to the right).
+
+const LONG_MESSAGE = `check https://example.com/${"averylongpathsegment-".repeat(12)}end and ${"Supercalifragilistic".repeat(14)} tail`;
+
+async function expectNoHorizontalOverflow(
+  page: import("@playwright/test").Page,
+) {
+  const overflow = await page.evaluate(() => {
+    const rootWidth = document.documentElement.clientWidth;
+    const shell = document.querySelector<HTMLElement>(
+      '[data-testid="dev-mode-shell"]',
+    );
+    if (!shell) return { missing: true, offenders: [] as string[] };
+    const offenders: string[] = [];
+    const walk = (el: HTMLElement) => {
+      // Ignore sub-pixel rounding; anything a pixel past the window is real.
+      if (el.getBoundingClientRect().right > rootWidth + 1) {
+        offenders.push(
+          `${el.tagName.toLowerCase()}[${el.dataset.testid ?? ""}] right=${Math.round(el.getBoundingClientRect().right)}`,
+        );
+      }
+      for (const child of el.children) walk(child as HTMLElement);
+    };
+    walk(shell);
+    return { missing: false, offenders: offenders.slice(0, 10) };
+  });
+  expect(overflow.missing).toBe(false);
+  expect(overflow.offenders).toEqual([]);
+}
+
+async function expectPaneContainsContent(
+  page: import("@playwright/test").Page,
+  testId: string,
+) {
+  const viewport = page.getByTestId(testId);
+  const widths = await viewport.evaluate((el) => ({
+    scrollWidth: el.scrollWidth,
+    clientWidth: el.clientWidth,
+  }));
+  expect(widths.scrollWidth).toBeLessThanOrEqual(widths.clientWidth + 1);
+}
+
+test("dev-mode chat content stays inside its pane", async ({ page }) => {
+  await page.setViewportSize({ width: 1000, height: 700 });
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+
+  // Open an existing channel: ArrowUp previews the newest channel, Enter opens.
+  await composer.focus();
+  await page.keyboard.press("ArrowUp");
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+
+  await composer.fill(LONG_MESSAGE);
+  await page.keyboard.press("Enter");
+  await expect(
+    page.getByTestId("dev-mode-transcript").getByText("tail", { exact: false }),
+  ).toBeVisible();
+
+  await expectNoHorizontalOverflow(page);
+  await expectPaneContainsContent(page, "dev-mode-transcript");
+
+  // Side chat splits the screen; both panes must still contain their content.
+  await page.keyboard.press("ArrowUp");
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-thread-panel").waitFor();
+
+  await expectNoHorizontalOverflow(page);
+  await expectPaneContainsContent(page, "dev-mode-transcript");
+});
diff --git a/desktop/tests/e2e/dev-mode-palette.spec.ts b/desktop/tests/e2e/dev-mode-palette.spec.ts
new file mode 100644
index 0000000000..6ffd94ea6a
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-palette.spec.ts
@@ -0,0 +1,153 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge, type MockBridgeOptions } from "../helpers/bridge";
+
+// Command-palette ranking and post-archive navigation: typing an action
+// verb like "archive" ranks that action above channels whose names merely
+// contain it, and archiving/leaving a chat lands on the most recently
+// active non-pinned chat instead of the fresh composer.
+
+async function openDevModeChannel(
+  page: import("@playwright/test").Page,
+  channelName: string,
+  mock?: MockBridgeOptions,
+) {
+  await installMockBridge(page, mock);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+  await composer.focus();
+
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  for (let step = 0; step < 20; step += 1) {
+    await page.keyboard.press("ArrowUp");
+    const previewed = (await topBar.innerText()).replace(/^#\s*/, "").trim();
+    if (previewed === channelName) break;
+  }
+  await expect(topBar).toContainText(channelName);
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+}
+
+test("typed action verb outranks channel-name matches in the palette", async ({
+  page,
+}) => {
+  await openDevModeChannel(page, "general");
+
+  // A channel whose name contains the verb would otherwise outrank the
+  // action (channels normally rank first while typing).
+  await page.evaluate(async () => {
+    const w = window as Window & {
+      __TAURI_INTERNALS__?: {
+        invoke: (command: string, payload: unknown) => Promise<unknown>;
+      };
+      __BUZZ_E2E_INVALIDATE_CHANNELS__?: () => Promise<void>;
+    };
+    await w.__TAURI_INTERNALS__?.invoke("create_channel", {
+      name: "team-archives",
+      channelType: "stream",
+      visibility: "open",
+    });
+    await w.__BUZZ_E2E_INVALIDATE_CHANNELS__?.();
+  });
+
+  await page.keyboard.press("Meta+k");
+  const palette = page.getByTestId("dev-mode-palette");
+  await expect(palette).toBeVisible();
+  await page.getByTestId("dev-mode-palette-input").pressSequentially("archiv");
+
+  const entries = page.getByTestId("dev-mode-palette-entry");
+  await expect(entries.first()).toContainText("archive # general");
+  await expect(
+    entries.filter({ hasText: "# team-archives" }).first(),
+  ).toBeVisible();
+});
+
+test("palette searches open channels the user hasn't joined and joins on enter", async ({
+  page,
+}) => {
+  await openDevModeChannel(page, "general");
+
+  // Seed a non-member open channel: create one, then leave it (the mock
+  // bridge drops membership without archiving).
+  await page.evaluate(async () => {
+    const w = window as Window & {
+      __TAURI_INTERNALS__?: {
+        invoke: (command: string, payload: unknown) => Promise<unknown>;
+      };
+      __BUZZ_E2E_INVALIDATE_CHANNELS__?: () => Promise<void>;
+    };
+    const created = (await w.__TAURI_INTERNALS__?.invoke("create_channel", {
+      name: "growth-experiments",
+      channelType: "stream",
+      visibility: "open",
+    })) as { id: string };
+    await w.__TAURI_INTERNALS__?.invoke("leave_channel", {
+      channelId: created.id,
+    });
+    await w.__BUZZ_E2E_INVALIDATE_CHANNELS__?.();
+  });
+
+  await page.keyboard.press("Meta+k");
+  const palette = page.getByTestId("dev-mode-palette");
+  await expect(palette).toBeVisible();
+  await page.getByTestId("dev-mode-palette-input").pressSequentially("growth");
+
+  const entry = page
+    .getByTestId("dev-mode-palette-entry")
+    .filter({ hasText: "# growth-experiments" })
+    .first();
+  await expect(entry).toContainText("not joined");
+  await page.keyboard.press("Enter");
+
+  // Joined and opened: the palette closes and the channel is now current.
+  await expect(palette).not.toBeVisible();
+  await expect(page.getByTestId("dev-mode-topbar-channel")).toContainText(
+    "growth-experiments",
+  );
+});
+
+test("archiving a chat lands on the most recent non-pinned chat", async ({
+  page,
+}) => {
+  await openDevModeChannel(page, "general");
+
+  await page.keyboard.press("Meta+k");
+  await page.getByTestId("dev-mode-palette-input").pressSequentially("archive");
+  const entries = page.getByTestId("dev-mode-palette-entry");
+  await expect(entries.first()).toContainText("archive # general");
+  await page.keyboard.press("Enter");
+
+  // Landed in another chat, not the fresh composer and not the archived one.
+  await expect(page.getByTestId("dev-mode-palette")).not.toBeVisible();
+  await page.getByTestId("dev-mode-transcript").waitFor();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  await expect(topBar).not.toContainText("general");
+  await expect(topBar).toContainText("#");
+});
+
+test("archive updates the UI optimistically, before the relay resolves", async ({
+  page,
+}) => {
+  // The mock relay sleeps 5s before acknowledging the archive; the palette
+  // must close and navigation must land elsewhere well before that.
+  await openDevModeChannel(page, "general", { archiveChannelDelayMs: 5_000 });
+
+  await page.keyboard.press("Meta+k");
+  await page.getByTestId("dev-mode-palette-input").pressSequentially("archive");
+  const entries = page.getByTestId("dev-mode-palette-entry");
+  await expect(entries.first()).toContainText("archive # general");
+
+  const start = Date.now();
+  await page.keyboard.press("Enter");
+
+  await expect(page.getByTestId("dev-mode-palette")).not.toBeVisible();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  await expect(topBar).not.toContainText("general");
+  await expect(topBar).toContainText("#");
+  expect(Date.now() - start).toBeLessThan(4_000);
+});
diff --git a/desktop/tests/e2e/dev-mode-shortcuts.spec.ts b/desktop/tests/e2e/dev-mode-shortcuts.spec.ts
new file mode 100644
index 0000000000..e960aef8df
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-shortcuts.spec.ts
@@ -0,0 +1,93 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge } from "../helpers/bridge";
+
+// Navigator rows open on the first click while keyboard ↑/↓ stays
+// preview-only (Enter opens), and the keyboard-shortcuts pane replaces the
+// visible key hints — opened with `?` in an empty composer or from the
+// command palette.
+
+async function openDevMode(page: import("@playwright/test").Page) {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+  await page.getByTestId("dev-mode-composer").waitFor();
+}
+
+test("clicking a navigator channel opens it immediately", async ({ page }) => {
+  await openDevMode(page);
+
+  await page
+    .getByTestId("dev-mode-channel-navigator")
+    .getByText("# general", { exact: true })
+    .click();
+
+  await expect(page.getByTestId("dev-mode-topbar-channel")).toContainText(
+    "general",
+  );
+  // Open, not previewing: no preview strip, and the composer targets the
+  // channel.
+  await expect(page.getByText("preview", { exact: true })).toHaveCount(0);
+  await expect(page.getByTestId("dev-mode-composer")).toHaveAttribute(
+    "placeholder",
+    /Message # general/,
+  );
+});
+
+test("keyboard ArrowUp previews; Enter is required to open", async ({
+  page,
+}) => {
+  await openDevMode(page);
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.focus();
+  await page.keyboard.press("ArrowUp");
+
+  await expect(page.getByText("preview", { exact: true })).toBeVisible();
+  await expect(page.getByTestId("dev-mode-topbar-channel")).toBeVisible();
+
+  await page.keyboard.press("Enter");
+  await expect(page.getByText("preview", { exact: true })).toHaveCount(0);
+  await expect(composer).toHaveAttribute("placeholder", /Message # /);
+});
+
+test("`?` in an empty composer opens the shortcuts pane", async ({ page }) => {
+  await openDevMode(page);
+
+  await page.getByTestId("dev-mode-composer").focus();
+  await page.keyboard.press("?");
+
+  const overlay = page.getByTestId("dev-mode-shortcuts-overlay");
+  await expect(overlay).toBeVisible();
+  await expect(overlay).toContainText("command palette");
+
+  await page.keyboard.press("Escape");
+  await expect(overlay).toHaveCount(0);
+  // Focus returns to the composer so typing resumes immediately.
+  await expect(page.getByTestId("dev-mode-composer")).toBeFocused();
+});
+
+test("`?` while text is present types normally", async ({ page }) => {
+  await openDevMode(page);
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.focus();
+  await composer.pressSequentially("what?");
+
+  await expect(page.getByTestId("dev-mode-shortcuts-overlay")).toHaveCount(0);
+  await expect(composer).toHaveValue("what?");
+});
+
+test("palette's keyboard-shortcuts entry opens the pane", async ({ page }) => {
+  await openDevMode(page);
+
+  await page.keyboard.press("Meta+k");
+  await page
+    .getByTestId("dev-mode-palette-input")
+    .pressSequentially("keyboard short");
+  await page.keyboard.press("Enter");
+
+  await expect(page.getByTestId("dev-mode-shortcuts-overlay")).toBeVisible();
+});
diff --git a/desktop/tests/e2e/dev-mode-sub-channels.spec.ts b/desktop/tests/e2e/dev-mode-sub-channels.spec.ts
new file mode 100644
index 0000000000..5e978dffbc
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-sub-channels.spec.ts
@@ -0,0 +1,202 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge } from "../helpers/bridge";
+
+// Sub-channels (`parent--sub`, surfaced to users as "tabs") in developer
+// mode: only main channels render in the left list; a parent's subs surface
+// as tabs across the top of the open channel, and "+ tab" drafts a prompt
+// whose Enter spawns a new sub-channel and announces it in the parent.
+
+async function openDevModeChannel(
+  page: import("@playwright/test").Page,
+  channelName: string,
+) {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const composer = page.getByTestId("dev-mode-composer");
+  await composer.waitFor();
+  await composer.focus();
+
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  for (let step = 0; step < 20; step += 1) {
+    await page.keyboard.press("ArrowUp");
+    const previewed = (await topBar.innerText()).replace(/^#\s*/, "").trim();
+    if (previewed === channelName) break;
+  }
+  await expect(topBar).toContainText(channelName);
+  await page.keyboard.press("Enter");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+}
+
+async function createChannel(
+  page: import("@playwright/test").Page,
+  name: string,
+) {
+  await page.evaluate(async (channelName) => {
+    const w = window as Window & {
+      __TAURI_INTERNALS__?: {
+        invoke: (command: string, payload: unknown) => Promise<unknown>;
+      };
+      __BUZZ_E2E_INVALIDATE_CHANNELS__?: () => Promise<void>;
+    };
+    await w.__TAURI_INTERNALS__?.invoke("create_channel", {
+      name: channelName,
+      channelType: "stream",
+      visibility: "open",
+    });
+    await w.__BUZZ_E2E_INVALIDATE_CHANNELS__?.();
+  }, name);
+}
+
+test("subs hide from the left list and surface as tabs in the parent", async ({
+  page,
+}) => {
+  await openDevModeChannel(page, "general");
+  await createChannel(page, "general--flaky-ci");
+  await createChannel(page, "general--rollback-plan");
+
+  // The left list shows the parent but neither sub.
+  const navigator = page.getByTestId("dev-mode-channel-navigator");
+  await expect(navigator.getByText("# general", { exact: true })).toBeVisible();
+  await expect(navigator.getByText("# general--flaky-ci")).toHaveCount(0);
+
+  // Tabs: main + one per sub, labeled by sub slug only.
+  const tabs = page.getByTestId("dev-mode-channel-tab");
+  await expect(tabs).toHaveCount(3);
+  await expect(tabs.nth(0)).toHaveText("main");
+  await expect(tabs.nth(1)).toHaveText("flaky-ci");
+  await expect(tabs.nth(2)).toHaveText("rollback-plan");
+  await expect(tabs.nth(0)).toHaveAttribute("data-active", "true");
+
+  // Switching tabs moves the transcript/composer to the sub-channel.
+  await tabs.nth(1).click();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  await expect(topBar).toContainText("general--flaky-ci");
+  await expect(tabs.nth(1)).toHaveAttribute("data-active", "true");
+
+  // Escape backs out to the navigator with the *parent* highlighted.
+  await page.keyboard.press("Escape");
+  await expect(navigator.getByText("# general", { exact: true })).toBeVisible();
+  await expect(navigator.getByText("▸")).toBeVisible();
+});
+
+test("+ tab drafts a prompt that spawns and announces a sub-channel", async ({
+  page,
+}) => {
+  await openDevModeChannel(page, "general");
+
+  await page.getByTestId("dev-mode-new-tab").click();
+  const composer = page.getByTestId("dev-mode-composer");
+  await expect(composer).toHaveAttribute(
+    "placeholder",
+    /spawns a new tab in # general/,
+  );
+
+  // The draft state gets an unmissable highlight banner, and Escape drops
+  // both the banner and the draft.
+  const banner = page.getByTestId("dev-mode-draft-banner");
+  await expect(banner).toContainText("new tab in # general");
+  await page.keyboard.press("Escape");
+  await expect(banner).not.toBeVisible();
+
+  // ⌘⇧T re-enters the draft.
+  await page.keyboard.press("Meta+Shift+t");
+  await expect(banner).toBeVisible();
+
+  await composer.pressSequentially("investigate the flaky deploy step");
+  await page.keyboard.press("Enter");
+
+  // Landed on the new sub-channel's tab.
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  await expect(topBar).toContainText("general--");
+  const activeTab = page.locator(
+    "[data-testid='dev-mode-channel-tab'][data-active]",
+  );
+  await expect(activeTab).not.toHaveText("main");
+
+  // The parent's main tab carries the spawn announcement.
+  await page.getByTestId("dev-mode-channel-tab").first().click();
+  await expect(topBar).toContainText("# general");
+  await expect(
+    page.getByTestId("dev-mode-transcript").getByText(/spawned #general--/),
+  ).toBeVisible();
+});
+
+test("palette offers a new tab action inside a channel", async ({ page }) => {
+  await openDevModeChannel(page, "general");
+
+  await page.keyboard.press("Meta+k");
+  await page.getByTestId("dev-mode-palette-input").pressSequentially("new tab");
+  const entries = page.getByTestId("dev-mode-palette-entry");
+  await expect(entries.first()).toContainText("new tab in # general");
+  await page.keyboard.press("Enter");
+
+  await expect(page.getByTestId("dev-mode-palette")).not.toBeVisible();
+  await expect(page.getByTestId("dev-mode-composer")).toHaveAttribute(
+    "placeholder",
+    /spawns a new tab in # general/,
+  );
+});
+
+test("⌘[ and ⌘] cycle through a channel's tabs", async ({ page }) => {
+  await openDevModeChannel(page, "general");
+  await createChannel(page, "general--flaky-ci");
+  await createChannel(page, "general--rollback-plan");
+
+  const tabs = page.getByTestId("dev-mode-channel-tab");
+  await expect(tabs).toHaveCount(3);
+  await expect(tabs.nth(0)).toHaveAttribute("data-active", "true");
+
+  await page.keyboard.press("Meta+]");
+  await expect(tabs.nth(1)).toHaveAttribute("data-active", "true");
+  await page.keyboard.press("Meta+]");
+  await expect(tabs.nth(2)).toHaveAttribute("data-active", "true");
+  // Wraps around past the last tab.
+  await page.keyboard.press("Meta+]");
+  await expect(tabs.nth(0)).toHaveAttribute("data-active", "true");
+  // ⌘[ goes the other way (wrapping back to the end).
+  await page.keyboard.press("Meta+[");
+  await expect(tabs.nth(2)).toHaveAttribute("data-active", "true");
+});
+
+test("palette rename edits a tab's suffix and cascades from the parent", async ({
+  page,
+}) => {
+  await openDevModeChannel(page, "general");
+  await createChannel(page, "general--flaky-ci");
+
+  // Renaming a tab only edits its suffix — the parent prefix is the link.
+  const tabs = page.getByTestId("dev-mode-channel-tab");
+  await tabs.nth(1).click();
+  await page.keyboard.press("Meta+k");
+  const input = page.getByTestId("dev-mode-palette-input");
+  await input.pressSequentially("rename");
+  const entries = page.getByTestId("dev-mode-palette-entry");
+  await expect(entries.first()).toContainText("rename # general--flaky-ci");
+  await page.keyboard.press("Enter");
+  await input.pressSequentially("Flaky CI Hunt");
+  await expect(entries.first()).toContainText(
+    "rename to # general--flaky-ci-hunt",
+  );
+  await page.keyboard.press("Enter");
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  await expect(topBar).toContainText("general--flaky-ci-hunt");
+  await expect(tabs.nth(1)).toHaveText("flaky-ci-hunt");
+
+  // Renaming the parent cascades: the sub follows and stays a tab.
+  await tabs.nth(0).click();
+  await page.keyboard.press("Meta+k");
+  await input.pressSequentially("rename");
+  await expect(entries.first()).toContainText("rename # general");
+  await page.keyboard.press("Enter");
+  await input.pressSequentially("war room");
+  await expect(entries.first()).toContainText("rename to # war-room");
+  await page.keyboard.press("Enter");
+  await expect(topBar).toContainText("war-room");
+  await expect(tabs).toHaveCount(2);
+  await expect(tabs.nth(1)).toHaveText("flaky-ci-hunt");
+});
diff --git a/desktop/tests/e2e/dev-mode-unread.spec.ts b/desktop/tests/e2e/dev-mode-unread.spec.ts
new file mode 100644
index 0000000000..7130317df7
--- /dev/null
+++ b/desktop/tests/e2e/dev-mode-unread.spec.ts
@@ -0,0 +1,337 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge, TEST_IDENTITIES } from "../helpers/bridge";
+
+// Contextual unread in developer mode: unread threads and tabs bubble up to
+// the parent's navigator row, and opening an unread parent routes directly
+// to the tab — and thread side chat — that needs attention, instead of
+// landing on the parent's main view.
+
+// The pubkey the mock bridge logs in as (mirrors `e2eBridge`'s self identity).
+const SELF_PUBKEY = "deadbeef".repeat(8);
+
+// Unread replies must land strictly after any read frontier captured while
+// the channel was open. A minute ahead ensures they do.
+function unreadTimestamp() {
+  return Math.floor(Date.now() / 1000) + 60;
+}
+
+async function openDevMode(page: import("@playwright/test").Page) {
+  await installMockBridge(page);
+  await page.addInitScript(() => {
+    localStorage.setItem("buzz.displayStyle", "developer");
+  });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+  await page.getByTestId("dev-mode-composer").waitFor();
+}
+
+// ArrowUp steps through channel previews newest-first; walk until the
+// target channel is previewed, then Enter opens it (with unread routing).
+async function openChannelFromNavigator(
+  page: import("@playwright/test").Page,
+  channelName: string,
+) {
+  await page.getByTestId("dev-mode-composer").focus();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  for (let step = 0; step < 20; step += 1) {
+    await page.keyboard.press("ArrowUp");
+    const previewed = (await topBar.innerText()).replace(/^#\s*/, "").trim();
+    if (previewed === channelName) break;
+  }
+  await expect(topBar).toContainText(channelName);
+  await page.keyboard.press("Enter");
+}
+
+async function createChannel(
+  page: import("@playwright/test").Page,
+  name: string,
+) {
+  await page.evaluate(async (channelName) => {
+    const w = window as Window & {
+      __TAURI_INTERNALS__?: {
+        invoke: (command: string, payload: unknown) => Promise<unknown>;
+      };
+      __BUZZ_E2E_INVALIDATE_CHANNELS__?: () => Promise<void>;
+    };
+    await w.__TAURI_INTERNALS__?.invoke("create_channel", {
+      name: channelName,
+      channelType: "stream",
+      visibility: "open",
+    });
+    await w.__BUZZ_E2E_INVALIDATE_CHANNELS__?.();
+  }, name);
+}
+
+async function waitForMockLiveSubscription(
+  page: import("@playwright/test").Page,
+  channelName: string,
+) {
+  await expect
+    .poll(async () =>
+      page.evaluate(
+        ({ ch }) =>
+          (
+            window as Window & {
+              __BUZZ_E2E_HAS_MOCK_LIVE_SUBSCRIPTION__?: (input: {
+                channelName: string;
+              }) => boolean;
+            }
+          ).__BUZZ_E2E_HAS_MOCK_LIVE_SUBSCRIPTION__?.({ channelName: ch }) ??
+          false,
+        { ch: channelName },
+      ),
+    )
+    .toBe(true);
+}
+
+async function emitMockMessage(
+  page: import("@playwright/test").Page,
+  channelName: string,
+  content: string,
+  options?: {
+    parentEventId?: string;
+    pubkey?: string;
+    createdAt?: number;
+    mentionPubkeys?: string[];
+  },
+): Promise<{ id: string }> {
+  const event = await page.evaluate(
+    ({ ch, msg, parentEventId, pubkey, ts, mentionPubkeys }) =>
+      (
+        window as Window & {
+          __BUZZ_E2E_EMIT_MOCK_MESSAGE__?: (input: {
+            channelName: string;
+            content: string;
+            parentEventId?: string;
+            pubkey?: string;
+            createdAt?: number;
+            mentionPubkeys?: string[];
+          }) => { id: string };
+        }
+      ).__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
+        channelName: ch,
+        content: msg,
+        parentEventId: parentEventId ?? undefined,
+        pubkey: pubkey ?? undefined,
+        createdAt: ts,
+        mentionPubkeys: mentionPubkeys ?? undefined,
+      }),
+    {
+      ch: channelName,
+      msg: content,
+      parentEventId: options?.parentEventId ?? null,
+      pubkey: options?.pubkey ?? TEST_IDENTITIES.alice.pubkey,
+      ts: options?.createdAt,
+      mentionPubkeys: options?.mentionPubkeys,
+    },
+  );
+  if (!event) {
+    throw new Error("Mock message emitter is not installed");
+  }
+  return event;
+}
+
+// The navigator row for a main channel, for asserting its unread dot.
+function navigatorRow(
+  page: import("@playwright/test").Page,
+  channelName: string,
+) {
+  return page
+    .getByTestId("dev-mode-channel-navigator")
+    .locator("button", { hasText: `# ${channelName}` })
+    .first();
+}
+
+test("collapsed unread replies in a tab route the parent open to the side chat", async ({
+  page,
+}) => {
+  await openDevMode(page);
+  await openChannelFromNavigator(page, "general");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+  await createChannel(page, "general--flaky-ci");
+
+  // Visit the tab once: establishes the live subscription and a read
+  // frontier strictly before the unread reply.
+  const tabs = page.getByTestId("dev-mode-channel-tab");
+  await expect(tabs).toHaveCount(2);
+  await tabs.nth(1).click();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  await expect(topBar).toContainText("general--flaky-ci");
+  await waitForMockLiveSubscription(page, "general--flaky-ci");
+
+  const root = await emitMockMessage(
+    page,
+    "general--flaky-ci",
+    "prompt: chase the flaky test",
+    { pubkey: SELF_PUBKEY, createdAt: Math.floor(Date.now() / 1000) - 40 },
+  );
+  await expect(
+    page.getByTestId("dev-mode-prompt-card").filter({
+      hasText: "prompt: chase the flaky test",
+    }),
+  ).toBeVisible();
+
+  // Back out to the fresh composer so nothing is being viewed.
+  await page.keyboard.press("Escape");
+  await page.keyboard.press("Escape");
+
+  // Two external human replies land while we are away: the first renders
+  // inline (human-first fallback), the second is collapsed behind the
+  // "… more replies" affordance — reading it requires the side chat. The
+  // self-mentions clear the notify gate exactly like replies to the
+  // user's prompt.
+  await emitMockMessage(page, "general--flaky-ci", "human: found the cause", {
+    parentEventId: root.id,
+    createdAt: unreadTimestamp(),
+    mentionPubkeys: [SELF_PUBKEY],
+  });
+  await emitMockMessage(page, "general--flaky-ci", "human: fix is up", {
+    parentEventId: root.id,
+    createdAt: unreadTimestamp() + 1,
+    mentionPubkeys: [SELF_PUBKEY],
+  });
+
+  // The thread unread bubbles to the parent's navigator row.
+  await expect(
+    navigatorRow(page, "general").getByTestId("dev-mode-unread-dot"),
+  ).toBeVisible();
+
+  // Opening the parent routes to the unread tab and opens the side chat on
+  // the unread thread, because part of it is not visible inline.
+  await openChannelFromNavigator(page, "general");
+  await expect(topBar).toContainText("general--flaky-ci");
+  await expect(tabs.filter({ hasText: "flaky-ci" }).first()).toHaveAttribute(
+    "data-active",
+    "true",
+  );
+  const threadPanel = page.getByTestId("dev-mode-thread-panel");
+  await expect(threadPanel).toBeVisible();
+  await expect(threadPanel).toContainText("human: fix is up");
+
+  // Reading the thread clears the contextual indicators.
+  await expect(
+    navigatorRow(page, "general").getByTestId("dev-mode-unread-dot"),
+  ).toHaveCount(0);
+});
+
+test("inline agent replies are read by viewing the channel, with no side chat", async ({
+  page,
+}) => {
+  await openDevMode(page);
+
+  // Visit the seeded "agents" channel (charlie is a bot member) to
+  // establish the live subscription and a read frontier.
+  await openChannelFromNavigator(page, "agents");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+  await waitForMockLiveSubscription(page, "agents");
+
+  const root = await emitMockMessage(
+    page,
+    "agents",
+    "prompt: roll out the fix",
+    { pubkey: SELF_PUBKEY, createdAt: Math.floor(Date.now() / 1000) - 40 },
+  );
+  await expect(
+    page.getByTestId("dev-mode-prompt-card").filter({
+      hasText: "prompt: roll out the fix",
+    }),
+  ).toBeVisible();
+
+  await page.keyboard.press("Escape");
+  await page.keyboard.press("Escape");
+
+  // A run of agent replies lands while we are away. All of them render
+  // inline in the main chat view (no human responded), so no side chat
+  // should be needed to read them.
+  await emitMockMessage(page, "agents", "agent: on it", {
+    parentEventId: root.id,
+    pubkey: TEST_IDENTITIES.charlie.pubkey,
+    createdAt: unreadTimestamp(),
+    mentionPubkeys: [SELF_PUBKEY],
+  });
+  await emitMockMessage(page, "agents", "agent: rollout complete", {
+    parentEventId: root.id,
+    pubkey: TEST_IDENTITIES.charlie.pubkey,
+    createdAt: unreadTimestamp() + 1,
+    mentionPubkeys: [SELF_PUBKEY],
+  });
+
+  await expect(
+    navigatorRow(page, "agents").getByTestId("dev-mode-unread-dot"),
+  ).toBeVisible();
+
+  // Opening the channel shows the whole agent run inline and marks it
+  // read — the side chat stays closed.
+  await openChannelFromNavigator(page, "agents");
+  const card = page.getByTestId("dev-mode-prompt-card").filter({
+    hasText: "prompt: roll out the fix",
+  });
+  await expect(card).toContainText("agent: on it");
+  await expect(card).toContainText("agent: rollout complete");
+  await expect(
+    navigatorRow(page, "agents").getByTestId("dev-mode-unread-dot"),
+  ).toHaveCount(0);
+  await expect(page.getByTestId("dev-mode-thread-panel")).toHaveCount(0);
+});
+
+test("unread top-level post routes to its tab without opening a side chat", async ({
+  page,
+}) => {
+  await openDevMode(page);
+  await openChannelFromNavigator(page, "general");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+  await createChannel(page, "general--rollback");
+
+  const tabs = page.getByTestId("dev-mode-channel-tab");
+  await expect(tabs).toHaveCount(2);
+  await tabs.nth(1).click();
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  await expect(topBar).toContainText("general--rollback");
+  await waitForMockLiveSubscription(page, "general--rollback");
+
+  await page.keyboard.press("Escape");
+  await page.keyboard.press("Escape");
+
+  await emitMockMessage(page, "general--rollback", "status: rollback done", {
+    createdAt: unreadTimestamp(),
+  });
+
+  await expect(
+    navigatorRow(page, "general").getByTestId("dev-mode-unread-dot"),
+  ).toBeVisible();
+
+  await openChannelFromNavigator(page, "general");
+  await expect(topBar).toContainText("general--rollback");
+  await expect(tabs.filter({ hasText: "rollback" }).first()).toHaveAttribute(
+    "data-active",
+    "true",
+  );
+  await expect(page.getByTestId("dev-mode-thread-panel")).toHaveCount(0);
+
+  // Viewing the tab clears the channel-level unread — no threads need to
+  // be opened.
+  await expect(
+    navigatorRow(page, "general").getByTestId("dev-mode-unread-dot"),
+  ).toHaveCount(0);
+});
+
+test("a read channel opens exactly where asked, with no routing", async ({
+  page,
+}) => {
+  await openDevMode(page);
+  await openChannelFromNavigator(page, "general");
+  await page.getByTestId("dev-mode-transcript").waitFor();
+  await createChannel(page, "general--quiet");
+
+  const tabs = page.getByTestId("dev-mode-channel-tab");
+  await expect(tabs).toHaveCount(2);
+
+  await page.keyboard.press("Escape");
+  await page.keyboard.press("Escape");
+
+  await openChannelFromNavigator(page, "general");
+  const topBar = page.getByTestId("dev-mode-topbar-channel");
+  await expect(topBar).toContainText("general");
+  await expect(tabs.nth(0)).toHaveAttribute("data-active", "true");
+  await expect(page.getByTestId("dev-mode-thread-panel")).toHaveCount(0);
+});
diff --git a/desktop/tests/helpers/bridge.ts b/desktop/tests/helpers/bridge.ts
index ca4d62ddd6..fcb4ba9dbb 100644
--- a/desktop/tests/helpers/bridge.ts
+++ b/desktop/tests/helpers/bridge.ts
@@ -272,6 +272,9 @@ type MockBridgeOptions = {
   profileUpdateErrors?: string[];
   searchProfiles?: MockSearchProfileSeed[];
   updateAvailable?: boolean;
+  /** Delay (ms) before mock `archive_channel` resolves, to test that the
+   *  UI updates optimistically without waiting on the relay. */
+  archiveChannelDelayMs?: number;
   updateChannelDelayMs?: number;
   updateDownloadDelayMs?: number;
   updateVersion?: string;
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 9ed8280c28..868b6a5501 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -84,6 +84,9 @@ importers:
       '@fontsource-variable/inter':
         specifier: ^5.2.8
         version: 5.2.8
+      '@fontsource-variable/jetbrains-mono':
+        specifier: ^5.3.0
+        version: 5.3.0
       '@mediapipe/tasks-vision':
         specifier: ^0.10.35
         version: 0.10.35
@@ -522,21 +525,18 @@ packages:
     engines: {node: '>=14.21.3'}
     cpu: [arm64]
     os: [linux]
-    libc: [musl]
 
   '@biomejs/cli-linux-arm64@2.4.16':
     resolution: {integrity: sha512-2kFb4//jxfZaP6D+Rj5VkHkxgyD9EoRAVBEQb8PKRv+s4NO2zYNJKXFaJmK1CmhufJOWEfpHKaRbOja7qjmdhQ==}
     engines: {node: '>=14.21.3'}
     cpu: [arm64]
     os: [linux]
-    libc: [glibc]
 
   '@biomejs/cli-linux-x64-musl@2.4.16':
     resolution: {integrity: sha512-iHDS+MCM65DPqWGu+ECC3uoALyj2H7F4nVUPxIPjz/PIl94EUu+EDfGZDzFP+NY1EOPVt9NQvwFqq7HdMmowdg==}
     engines: {node: '>=14.21.3'}
     cpu: [x64]
     os: [linux]
-    libc: [musl]
 
   '@biomejs/cli-linux-x64@2.4.16':
     resolution: {integrity: sha512-NbcBbi/nJqn5baae6wqRXdS7Gadf2uRpehSh6vMSYpG8OhkXl/Xg8aorWrJ+9VWqAT5ml90alLvorkpMW0nBwQ==}
@@ -660,6 +660,9 @@ packages:
   '@fontsource-variable/inter@5.2.8':
     resolution: {integrity: sha512-kOfP2D+ykbcX/P3IFnokOhVRNoTozo5/JxhAIVYLpea/UBmCQ/YWPBfWIDuBImXX/15KH+eKh4xpEUyS2sQQGQ==}
 
+  '@fontsource-variable/jetbrains-mono@5.3.0':
+    resolution: {integrity: sha512-F32xpS2NsGYoQi2ADSkKTgpJj7ozajsGgDJ8woTnqjmIB+dxDIqImjl4pXZVEExu8UFZ2ndhmX18EBS/hdz3Lw==}
+
   '@isomorphic-git/idb-keyval@3.3.2':
     resolution: {integrity: sha512-r8/AdpiS0/WJCNR/t/gsgL+M8NMVj/ek7s60uz3LmpCaTF2mEVlZJlB01ZzalgYzRLXwSPC92o+pdzjM7PN/pA==}
 
@@ -1783,7 +1786,6 @@ packages:
     engines: {node: '>= 10'}
     cpu: [arm64]
     os: [linux]
-    libc: [glibc]
 
   '@tauri-apps/cli-linux-arm64-musl@2.11.2':
     resolution: {integrity: sha512-X1rm0BERqAAggtYTESSgXrS3sz4Sb/OiPiz54UqISlXW+GkR3vNIGnsy/lejNmoXGVqri3Q53BCfQiclOIyRPw==}
@@ -3664,7 +3666,7 @@ packages:
     engines: {node: '>=8'}
 
   wrappy@1.0.2:
-    resolution: {integrity: sha512-l4Sp/DRseor9wL6EvV2+TuQn63dMkPjZ/sp9XkghTEbV9KlPS1xUsZ3u7/IQO4wxtcFB4bgpQPRcR3QCvezPcQ==}
+    resolution: {integrity: sha1-tSQ9jz7BqjXxNkYFvA0QNuMKtp8=}
 
   ws@8.21.1:
     resolution: {integrity: sha512-+0NTnW77fFN/DjQi6k/Sq/Yvk4Sgajw7urW8V+asjXnRgDs9gyGkdb7EzgfhA4goXsRIZKE28fzIXBHEzhuiWw==}
@@ -3988,6 +3990,8 @@ snapshots:
 
   '@fontsource-variable/inter@5.2.8': {}
 
+  '@fontsource-variable/jetbrains-mono@5.3.0': {}
+
   '@isomorphic-git/idb-keyval@3.3.2': {}
 
   '@isomorphic-git/lightning-fs@4.6.2':