feat(acp): add Letta as a tier-2 preset harness

crates/buzz-acp/README.md

@@ -9,7 +9,7 @@ Buzz Relay ──WS──→ buzz-acp ──stdio──→ Your Agent
                                        (send_message, etc.)
 ```
 
-Supports any agent that speaks [ACP](https://agentclientprotocol.com/) over stdio: **goose**, **codex** (via [codex-acp](https://github.com/agentclientprotocol/codex-acp)), and **claude code** (via [claude-agent-acp](https://github.com/agentclientprotocol/claude-agent-acp)).
+Supports any agent that speaks [ACP](https://agentclientprotocol.com/) over stdio: **goose**, **codex** (via [codex-acp](https://github.com/agentclientprotocol/codex-acp)), **claude code** (via [claude-agent-acp](https://github.com/agentclientprotocol/claude-agent-acp)), and **letta** (via [letta-acp](https://github.com/letta-ai/letta-acp)).
 
 ## Prerequisites
 
@@ -98,6 +98,47 @@ buzz-acp
 Older installs that still expose `claude-code-acp` are also supported. `buzz-acp`
 treats both Claude ACP command names as the same zero-arg runtime.
 
+## Running with Letta
+
+[letta-acp](https://github.com/letta-ai/letta-acp) exposes a [Letta](https://docs.letta.com)
+agent over ACP. Letta agents are stateful: memory persists across sessions, so
+the same agent carries context between channels and across harness restarts.
+
+```bash
+# Install the adapter (npm package — no Rust build required)
+npm install -g @letta-ai/letta-acp
+
+# Run
+export LETTA_AGENT_ID="agent-..."   # optional: pin one persistent agent
+export BUZZ_ACP_AGENT_COMMAND="letta-acp"
+
+buzz-acp
+```
+
+Without `LETTA_AGENT_ID` the adapter creates an agent on first use and logs its
+id to stderr; set the variable to that value to keep every run on the same
+agent. Each channel session becomes its own conversation on that one agent.
+
+### Letta backends
+
+`LETTA_ACP_BACKEND` selects where the agent lives and where its tools run.
+Since the agent answers Buzz by shelling out to the `buzz` CLI, the CLI and
+the `BUZZ_*` environment have to be wherever the tools run:
+
+| `LETTA_ACP_BACKEND` | Agent state | Tools run | Extra config |
+|---|---|---|---|
+| `local` (default) | this machine | this machine | `letta login`, or `letta --backend local connect anthropic --api-key ...` for model access |
+| `cloud-oauth` | Letta Cloud | this machine | `letta login` once; no key in the harness env |
+| `remote` | your app server | the app server | `LETTA_APP_SERVER_URL`, `LETTA_APP_SERVER_TOKEN`; install the `buzz` CLI there |
+| `cloud` | Letta Cloud | Letta's sandbox | not usable from Buzz — the sandbox has no `buzz` CLI |
+
+`local` and `cloud-oauth` need nothing beyond the harness environment they
+already inherit; `cloud-oauth` is the way to run a cloud-hosted agent whose
+tools still execute here. Plain `cloud` puts tool execution in Letta's
+sandbox, out of reach of the `buzz` CLI, and MCP servers passed through
+`BUZZ_ACP_MCP_COMMAND` do not close the gap: the sandbox has no executor for
+adapter-side tools.
+
 ## Configuration
 
 All configuration is via environment variables (or CLI flags — every env var has a matching flag).
@@ -269,7 +310,7 @@ Buzz Desktop supports registering any ACP-speaking agent tool as a selectable ru
 
 **Tier-1 — compiled-in runtimes** (Goose, Claude Code, Codex, Buzz Agent): have auto-installers, auth probes, and first-class onboarding. Their IDs (`goose`, `claude`, `codex`, `buzz-agent`) are reserved and cannot be overridden.
 
-**Tier-2 — preset catalog** (Cursor, Oh My Pi, Grok Build, OpenCode, Kimi Code, Amp, Hermes Agent, OpenClaw): static `HarnessDefinition` entries in `desktop/src-tauri/src/managed_agents/discovery.rs` (`PRESET_HARNESSES`). They are always present in the runtime catalog, PATH-probed for availability, not editable or deletable by the user. Displayed with bundled logos; if not installed, a docs link appears instead.
+**Tier-2 — preset catalog** (Cursor, Oh My Pi, Grok Build, OpenCode, Kimi Code, Amp, Letta, Hermes Agent, OpenClaw): static `HarnessDefinition` entries in `desktop/src-tauri/src/managed_agents/discovery.rs` (`PRESET_HARNESSES`). They are always present in the runtime catalog, PATH-probed for availability, not editable or deletable by the user. Displayed with bundled logos; if not installed, a docs link appears instead.
 
 > **Note — OpenClaw:** `openclaw acp` is a Gateway-backed bridge; PATH availability shows "Available" even when the OpenClaw Gateway daemon is not running. This is expected tier-2 semantics (same class as a preset with unconfigured auth). The Gateway URL is configured via `OPENCLAW_GATEWAY_URL` (or the equivalent env var from OpenClaw's docs) — set it in the agent's **env vars** in Edit Agent, not in the definition env (the preset definition carries no env entries). Note that `openclaw acp` executes tools inside the Gateway daemon, not the Desktop process, so Desktop-injected `BUZZ_*` env vars do NOT reach the execution locus unless you also set them on the Gateway's own environment.
 

crates/buzz-acp/src/config.rs

@@ -689,7 +689,7 @@ fn default_agent_args(command: &str) -> Option<Vec<String>> {
     match normalize_agent_command_identity(command).as_str() {
         "goose" => Some(vec!["acp".to_string()]),
         "codex" | "codex-acp" | "claude-agent-acp" | "claude-code-acp" | "claude-code"
-        | "claudecode" | "buzz-agent" => Some(Vec::new()),
+        | "claudecode" | "buzz-agent" | "letta-acp" => Some(Vec::new()),
         _ => None,
     }
 }
@@ -1542,6 +1542,16 @@ mod tests {
             normalize_agent_args("claude-agent-acp", vec!["acp".into()]),
             Vec::<String>::new()
         );
+        // letta-acp speaks ACP on stdin with no subcommand, so the legacy
+        // Goose-shaped "acp" default must not reach it as a positional.
+        assert_eq!(
+            normalize_agent_args("letta-acp", vec!["acp".into()]),
+            Vec::<String>::new()
+        );
+        assert_eq!(
+            normalize_agent_args("letta-acp", Vec::new()),
+            Vec::<String>::new()
+        );
     }
 
     #[test]

desktop/public/harness-logos/CREDITS.md

@@ -25,6 +25,7 @@ Monochrome marks inlined as `currentColor` paths in
 |---|---|---|---|---|---|
 | Goose | [block/goose](https://github.com/block/goose) | `305849b71709b95b86ed9f11bd3bc939899c0aab` | Apache-2.0 © Block, Inc. | `documentation/static/img/goose.svg` | `fill="#101010"` → `currentColor`; dropped the redundant clipPath wrapper |
 | Cursor | [simple-icons](https://github.com/simple-icons/simple-icons) | `16.27.1` (slug `cursor`) | CC0-1.0 (path data); nominative use of the Cursor mark to identify Cursor's harness | `icons/cursor.svg` | `fill` → `currentColor` |
+| Letta | [letta-ai/letta-evals](https://github.com/letta-ai/letta-evals) | `2daaf0c598780b6fa2edc26de52348de127f88a5` | Apache-2.0 © Letta | `leaderboard_site/src/letta-logo.svg` | Dropped the per-path `fill` attributes (the root `fill="currentColor"` already carries them) and the fixed `width`/`height` |
 
 Codex deliberately has **no** bundled mark: the OpenAI blossom was removed
 from simple-icons in v16 at the vendor's request, so we do not ship it —

desktop/src-tauri/src/managed_agents/discovery.rs

@@ -10,8 +10,11 @@ use crate::managed_agents::{
     HarnessSource,
 };
 
+mod presets;
 mod runtime_metadata;
 
+pub(crate) use presets::{preset_harness_definitions, preset_harness_ids};
+use presets::{PresetHarness, PRESET_HARNESSES};
 pub(crate) use runtime_metadata::KnownAcpRuntime;
 
 const GOOSE_AVATAR_URL: &str = "https://goose-docs.ai/img/logo_dark.png";
@@ -1436,33 +1439,6 @@ pub(crate) fn discover_acp_runtime_availability(runtime_id: &str) -> Option<AcpA
         .map(|partial| partial.entry.availability)
 }
 
-// ── Tier-2 preset harnesses ────────────────────────────────────────────────
-//
-// Static data for well-known ACP harnesses that have bundled logos and
-// verified command/args. PATH-probed at discovery time (Detected badge);
-// not editable or deletable by users. Logos are bundled assets referenced
-// by id in the frontend `RUNTIME_LOGOS` map.
-
-struct PresetHarness {
-    id: &'static str,
-    label: &'static str,
-    command: &'static str,
-    args: &'static [&'static str],
-    install_instructions_url: &'static str,
-    install_hint: &'static str,
-    /// Vendor CLI the ACP command wraps, when the preset is an adapter
-    /// (e.g. Amp's `amp-acp` wraps the separately-installed `amp` CLI).
-    /// Consulted only when the adapter is absent, so `AdapterMissing`
-    /// replaces the misleading `NotInstalled` when the CLI is present but
-    /// the adapter is not. Deliberately NOT fed through the builtins'
-    /// full `classify_runtime` predicate: that would flip
-    /// adapter-present/CLI-absent from today's `Available` to `CliMissing`
-    /// (unselectable), and presets carry a single flat `install_hint`, so
-    /// the `CliMissing` copy would tell the user to install the adapter
-    /// they already have. `None` when the command IS the vendor CLI.
-    underlying_cli: Option<&'static str>,
-}
-
 /// Build the catalog entry for one preset harness through an injectable
 /// resolver — the seam the preset loop consumes and tests bind.
 ///
@@ -1537,124 +1513,6 @@ fn preset_catalog_entry(
     }
 }
 
-const PRESET_HARNESSES: &[PresetHarness] = &[
-    PresetHarness {
-        id: "cursor",
-        label: "Cursor",
-        command: "cursor-agent",
-        args: &["acp"],
-        install_instructions_url: "https://cursor.com/downloads",
-        install_hint: "Buzz talks to Cursor through the cursor-agent CLI's ACP mode.",
-        underlying_cli: None,
-    },
-    PresetHarness {
-        id: "omp",
-        label: "Oh My Pi",
-        command: "omp",
-        args: &["acp"],
-        install_instructions_url: "https://github.com/can1357/oh-my-pi",
-        install_hint: "Buzz talks to Oh My Pi through its CLI's ACP mode (omp acp).",
-        underlying_cli: None,
-    },
-    PresetHarness {
-        id: "grok",
-        label: "Grok Build",
-        command: "grok",
-        args: &["agent", "--always-approve", "stdio"],
-        install_instructions_url: "https://build.x.ai/docs",
-        install_hint: "Buzz talks to Grok Build through its CLI's agent stdio mode.",
-        underlying_cli: None,
-    },
-    PresetHarness {
-        id: "opencode",
-        label: "OpenCode",
-        command: "opencode",
-        args: &["acp"],
-        install_instructions_url: "https://opencode.ai/docs",
-        install_hint: "Buzz talks to OpenCode through its CLI's ACP mode (opencode acp).",
-        underlying_cli: None,
-    },
-    PresetHarness {
-        id: "kimi",
-        label: "Kimi Code",
-        command: "kimi",
-        args: &["acp"],
-        install_instructions_url: "https://kimi.ai/download",
-        install_hint: "Buzz talks to Kimi Code through its CLI's ACP mode (kimi acp).",
-        underlying_cli: None,
-    },
-    PresetHarness {
-        id: "amp",
-        label: "Amp",
-        command: "amp-acp",
-        args: &[],
-        install_instructions_url: "https://github.com/tao12345666333/amp-acp",
-        install_hint: "Buzz talks to the Amp CLI through the amp-acp adapter. Follow the setup guide to install the adapter so the amp-acp command is on your PATH.",
-        underlying_cli: Some("amp"),
-    },
-    PresetHarness {
-        id: "hermes",
-        label: "Hermes Agent",
-        command: "hermes-acp",
-        args: &[],
-        install_instructions_url: "https://hermes-agent.nousresearch.com",
-        install_hint: "Buzz talks to Hermes Agent through its hermes-acp command.",
-        underlying_cli: None,
-    },
-    PresetHarness {
-        id: "openclaw",
-        label: "OpenClaw",
-        command: "openclaw",
-        args: &["acp"],
-        install_instructions_url: "https://docs.openclaw.ai/start/getting-started",
-        install_hint: "Buzz talks to OpenClaw through its ACP mode (openclaw acp), which relies on the OpenClaw Gateway daemon. Follow the setup guide to install both.\n\n\
-            ⚠️  Execution-locus note: `openclaw acp` runs tools inside the \
-            OpenClaw Gateway daemon, not in the Desktop process. \
-            Desktop-injected BUZZ_* env vars are visible to the `openclaw` \
-            harness process itself, but do NOT automatically reach the \
-            Gateway's execution environment. If your tools or agent logic \
-            needs BUZZ_* credentials at execution time, set them on the \
-            Gateway's own environment separately.",
-        underlying_cli: None,
-    },
-];
-
-/// Return the static preset harness definitions as `HarnessDefinition` values.
-///
-/// Used by `warm_harness_registry_from_dir` to seed the loaded-harness registry
-/// at startup before the frontend triggers a full discovery run.
-pub(crate) fn preset_harness_definitions(
-) -> Vec<crate::managed_agents::custom_harnesses::HarnessDefinition> {
-    PRESET_HARNESSES
-        .iter()
-        .map(
-            |p| crate::managed_agents::custom_harnesses::HarnessDefinition {
-                id: p.id.to_string(),
-                label: p.label.to_string(),
-                command: p.command.to_string(),
-                args: p.args.iter().map(|s| s.to_string()).collect(),
-                env: std::collections::BTreeMap::new(),
-                install_instructions_url: p.install_instructions_url.to_string(),
-                install_hint: p.install_hint.to_string(),
-            },
-        )
-        .collect()
-}
-
-/// Return the static slice of preset harness IDs.
-///
-/// Used by `check_id_collision` in `custom_harnesses` to derive the reserved-ID
-/// set from the single source of truth (`PRESET_HARNESSES`) rather than a
-/// hand-maintained copy.  Adding a preset automatically reserves its ID.
-pub(crate) fn preset_harness_ids() -> &'static [&'static str] {
-    // `PRESET_HARNESSES` is `'static`; we project its `id` fields.
-    // Computed once via OnceLock to avoid repeated allocations on hot paths.
-    use std::sync::OnceLock;
-    static IDS: OnceLock<Vec<&'static str>> = OnceLock::new();
-    IDS.get_or_init(|| PRESET_HARNESSES.iter().map(|p| p.id).collect())
-        .as_slice()
-}
-
 /// Discover all ACP runtimes, optionally merging user-defined custom harnesses
 /// from `custom_harnesses_dir`.
 ///