diff --git a/.specs/features/open-worktree-prompt/spec.md b/.specs/features/open-worktree-prompt/spec.md
new file mode 100644
index 0000000..bd441e1
--- /dev/null
+++ b/.specs/features/open-worktree-prompt/spec.md
@@ -0,0 +1,12 @@
+# Open worktree prompt
+
+- OWP-01: For an interactive `open` without worktree flags or `--resume`, ask once after role resolution and before starting the daemon when cwd is in a git repository.
+- OWP-02: A trimmed, case-insensitive `y` or `yes` enables `opts.worktree` and follows the existing `--worktree` launch path.
+- OWP-03: An empty answer, `n`, or `no` continues without a worktree.
+- OWP-04: Any other answer prints `Answer y or n.` to stderr and asks again.
+- OWP-05: EOF rejects with `Worktree selection was interrupted; nothing was launched.` before the daemon starts or a session is adopted.
+- OWP-06: `--worktree` skips the question and opens in a worktree.
+- OWP-07: `--no-worktree` skips the question and opens in the current directory; omitting both flags leaves the option undefined.
+- OWP-08: Non-interactive launches, including no-TTY and `-p`/`--print`, do not ask and do not use a worktree by default.
+- OWP-09: A cwd outside a git repository does not trigger the question.
+- OWP-10: `--resume` without `--worktree` does not trigger the question.
diff --git a/README.md b/README.md
index 8c38371..2a6ad2b 100644
--- a/README.md
+++ b/README.md
@@ -126,7 +126,7 @@ Two things worth knowing before you edit an agent file. `--agent` layers on top
 npx codedeck run "review the diff on this branch" --agent codex --role reviewer
 ```
 
-`--no-bypass` drops the bypass flag, `--no-theme` keeps the status line but drops everything else the look changes, `--no-pty` opts out of the session naming itself, and `--model`/`--effort`/`--resume`/`--worktree` override the defaults.
+`--no-bypass` drops the bypass flag, `--no-theme` keeps the status line but drops everything else the look changes, `--no-pty` opts out of the session naming itself, and `--model`/`--effort`/`--resume`/`--worktree` override the defaults. Interactive opens ask about a worktree when neither `--worktree` nor `--no-worktree` is set.
 
 ### What the session looks like
 
diff --git a/scripts/pty-gate.sh b/scripts/pty-gate.sh
index 91da827..166b56a 100755
--- a/scripts/pty-gate.sh
+++ b/scripts/pty-gate.sh
@@ -89,7 +89,7 @@ chmod +x "$WORK/bin/claude"
   sleep 2
 ) | RUN_AGENT_CONFIG_DIR="$CONFIG_DIR" RUN_AGENT_DIR="$STATE_DIR" PATH="$WORK/bin:$PATH" FAKE_NAME="$NAME" \
   timeout "$LIMIT" script -qec \
-    "sh -c 'stty rows $ROWS cols $COLS; exec node \"$HERE/dist/cli/index.js\" open general --effort xhigh --no-theme'" \
+    "sh -c 'stty rows $ROWS cols $COLS; exec node \"$HERE/dist/cli/index.js\" open general --effort xhigh --no-theme --no-worktree'" \
     /dev/null > "$CAPTURE" 2>&1 || true
 
 failures=()
diff --git a/scripts/rename-gate.sh b/scripts/rename-gate.sh
index 65de614..b2b0690 100755
--- a/scripts/rename-gate.sh
+++ b/scripts/rename-gate.sh
@@ -54,7 +54,7 @@ echo "expecting the session to rename itself to the generated title"
 # --no-bypass keeps the gate runnable as root, where Claude Code refuses to
 # skip permission prompts. It changes nothing about the rename path.
 ( sleep "$SETTLE"; printf '%s\r' "$PROMPT"; sleep "$TURN"; printf '\003'; sleep 1; printf '\003'; sleep 2 ) \
-  | timeout "$LIMIT" script -qec "node '$HERE/dist/cli/index.js' open general --no-bypass" /dev/null \
+  | timeout "$LIMIT" script -qec "node '$HERE/dist/cli/index.js' open general --no-bypass --no-worktree" /dev/null \
   > "$CAPTURE" 2>&1 || true
 
 sidecar="$(ls -t "$SESSIONS"/codedeck-session-*.name 2>/dev/null | head -1 || true)"
diff --git a/scripts/theme-gate.sh b/scripts/theme-gate.sh
index e0e2749..c4ac719 100755
--- a/scripts/theme-gate.sh
+++ b/scripts/theme-gate.sh
@@ -69,7 +69,7 @@ echo "expecting promptBorder $prompt_border and inactive $inactive"
 # A pty is required: claude renders nothing recognisable when stdout is a pipe.
 # `script` supplies one. Two Ctrl+C keys are how the TUI is asked to quit.
 ( sleep "$SETTLE"; printf '\003'; sleep 1; printf '\003'; sleep 2 ) \
-  | timeout "$LIMIT" script -qec "node '$HERE/dist/cli/index.js' open general" /dev/null \
+  | timeout "$LIMIT" script -qec "node '$HERE/dist/cli/index.js' open general --no-worktree" /dev/null \
   > "$CAPTURE" 2>&1 || true
 
 missing=()
diff --git a/src/cli/commands/open.ts b/src/cli/commands/open.ts
index 6bd105b..6cc638d 100644
--- a/src/cli/commands/open.ts
+++ b/src/cli/commands/open.ts
@@ -367,6 +367,62 @@ function selectRole(): Promise<Role> {
   });
 }
 
+export function askWorktree(): Promise<boolean> {
+  const rl = readline.createInterface({
+    input: process.stdin,
+    output: process.stdout,
+  });
+
+  return new Promise<boolean>((resolve, reject) => {
+    let settled = false;
+    const finish = (worktree: boolean) => {
+      if (settled) return;
+      settled = true;
+      rl.close();
+      resolve(worktree);
+    };
+
+    rl.once("close", () => {
+      if (settled) return;
+      settled = true;
+      reject(new Error("Worktree selection was interrupted; nothing was launched."));
+    });
+
+    const ask = () => {
+      rl.question("Open in a worktree? [y/N]: ", (answer) => {
+        const choice = answer.trim().toLowerCase();
+        if (choice === "y" || choice === "yes") {
+          finish(true);
+          return;
+        }
+        if (choice === "" || choice === "n" || choice === "no") {
+          finish(false);
+          return;
+        }
+
+        process.stderr.write("Answer y or n.\n");
+        ask();
+      });
+    };
+
+    ask();
+  });
+}
+
+export async function resolveOpenWorktree(
+  flag: boolean | undefined,
+  ctx: { interactive: boolean; resume?: string; cwd: string },
+  ask: () => Promise<boolean> = askWorktree,
+): Promise<boolean> {
+  if (flag !== undefined) return flag;
+  if (!ctx.interactive || ctx.resume !== undefined) return false;
+
+  const gitInfo = await getGitInfo(ctx.cwd);
+  if (!gitInfo) return false;
+
+  return ask();
+}
+
 /**
  * `claude -p` answers one prompt and exits, so there is no session to choose a
  * role for. A terminal check alone does not catch this: under a pty (CI scripts,
@@ -520,7 +576,8 @@ export function registerOpenCommand(program: Command): void {
     .option("--autocompact [value]", "native auto-compact: Claude window size is auto or 100000-1000000 tokens; OpenCode toggles its native setting")
     .option("--no-autocompact", "disable native auto-compaction in Claude and OpenCode")
     .option("--resume <session>", "resume an interactive session")
-    .option("--worktree", "ask Claude Code to create an isolated worktree")
+    .option("--worktree", "open the session in an isolated git worktree")
+    .option("--no-worktree", "open in the current directory without asking")
     .option("--profile <name>", "use a saved setup profile instead of the active one (see profile list)")
     .option("--no-bypass", "do not skip Claude Code permission prompts")
     .option("--no-theme", "keep only the CodeDeck status line, without the theme or the renderer")
@@ -549,9 +606,14 @@ export function registerOpenCommand(program: Command): void {
       }
       const interactive = !isNonInteractiveLaunch(invocation.passthrough, hintLauncher);
       const role = await resolveRole(invocation.roleInput, interactive);
+      const cwd = currentWorkingDirectory();
+      opts.worktree = await resolveOpenWorktree(opts.worktree, {
+        interactive: interactive && isInteractiveTerminal(),
+        resume: opts.resume,
+        cwd,
+      });
       const pluginDir = resolvePluginDir();
       assertPluginDirectory(pluginDir);
-      const cwd = currentWorkingDirectory();
 
       const client = new IpcClient();
       await client.ensureDaemonStarted();
diff --git a/tests/open-worktree-prompt.test.ts b/tests/open-worktree-prompt.test.ts
new file mode 100644
index 0000000..ac35967
--- /dev/null
+++ b/tests/open-worktree-prompt.test.ts
@@ -0,0 +1,243 @@
+import { Command } from "commander";
+import * as readline from "node:readline";
+import { describe, expect, it, vi } from "vitest";
+
+import { IpcClient } from "../src/daemon/ipc.js";
+import * as repository from "../src/git/repository.js";
+import * as worktree from "../src/git/worktree.js";
+import * as runtime from "../src/open/runtime.js";
+import * as setupCommands from "../src/cli/commands/setup.js";
+import {
+  askWorktree,
+  registerOpenCommand,
+  resolveOpenWorktree,
+  scanOptions,
+} from "../src/cli/commands/open.js";
+import { setupOpenHarness } from "./helpers/open-harness.js";
+
+const { createInterfaceMock } = vi.hoisted(() => ({ createInterfaceMock: vi.fn() }));
+
+vi.mock("node:readline", () => ({ createInterface: createInterfaceMock }));
+
+vi.mock("node:child_process", async (importOriginal) => {
+  const mod = await importOriginal<typeof import("node:child_process")>();
+  return { ...mod, execFileSync: vi.fn() };
+});
+
+const { runOpen } = setupOpenHarness({ prefix: "codedeck-worktree-prompt-", restoreCwd: true });
+
+interface FakeReadline {
+  instance: {
+    question: ReturnType<typeof vi.fn>;
+    once: ReturnType<typeof vi.fn>;
+    close: ReturnType<typeof vi.fn>;
+  };
+  prompts: string[];
+}
+
+function mockReadline(...answerSets: Array<Array<string | "close">>): FakeReadline[] {
+  let nextAnswerSet = 0;
+  const fakes: FakeReadline[] = answerSets.map((answers) => {
+    let closeHandler: (() => void) | undefined;
+    const prompts: string[] = [];
+    return {
+      prompts,
+      instance: {
+        question: vi.fn((prompt: string, callback: (answer: string) => void) => {
+          prompts.push(prompt);
+          const answer = answers.shift();
+          if (answer === "close") {
+            closeHandler?.();
+            return;
+          }
+          if (answer === undefined) throw new Error("Unexpected readline question");
+          callback(answer);
+        }),
+        once: vi.fn((event: string, callback: () => void) => {
+          if (event === "close") closeHandler = callback;
+        }),
+        close: vi.fn(),
+      },
+    };
+  });
+
+  createInterfaceMock.mockClear();
+  createInterfaceMock.mockImplementation(() => {
+    const fake = fakes[nextAnswerSet];
+    if (!fake) throw new Error("Unexpected readline interface");
+    nextAnswerSet += 1;
+    return fake.instance as unknown as readline.Interface;
+  });
+  return fakes;
+}
+
+describe("open worktree prompt", () => {
+  it("OWP-01 asks once for an interactive launch in a git repository", async () => {
+    vi.spyOn(repository, "getGitInfo").mockResolvedValue({
+      root: "/repo",
+      head: "abc",
+      branch: "main",
+      isDirty: false,
+    });
+    const ask = vi.fn().mockResolvedValue(false);
+
+    await expect(
+      resolveOpenWorktree(undefined, { interactive: true, cwd: "/repo" }, ask),
+    ).resolves.toBe(false);
+
+    expect(ask).toHaveBeenCalledTimes(1);
+    expect(repository.getGitInfo).toHaveBeenCalledWith("/repo");
+  });
+
+  it("OWP-02 treats y and trimmed uppercase YES as yes and launches in the created worktree", async () => {
+    const choices = mockReadline(["y"], ["  YES  "]);
+    await expect(askWorktree()).resolves.toBe(true);
+    expect(choices[0].prompts).toEqual(["Open in a worktree? [y/N]: "]);
+
+    vi.spyOn(setupCommands, "isInteractiveTerminal").mockReturnValue(true);
+    vi.spyOn(repository, "getGitInfo").mockResolvedValue({
+      root: "/repo",
+      head: "abc",
+      branch: "main",
+      isDirty: false,
+    });
+    const create = vi
+      .spyOn(worktree, "createWorktree")
+      .mockResolvedValue({ path: "/wt/yes", branch: "ra/reviewer-yes", baseCommit: "abc" });
+
+    await runOpen(["reviewer", "--no-theme"]);
+
+    expect(choices[1].prompts).toEqual(["Open in a worktree? [y/N]: "]);
+    expect(create).toHaveBeenCalledWith(expect.objectContaining({ repoRoot: "/repo", name: "reviewer" }));
+    const [, , spawnOptions] = vi.mocked(runtime.spawnHarness).mock.calls[0];
+    expect(spawnOptions.cwd).toBe("/wt/yes");
+    expect(choices[1].instance.question.mock.invocationCallOrder[0]).toBeLessThan(
+      vi.mocked(IpcClient.prototype.ensureDaemonStarted).mock.invocationCallOrder[0],
+    );
+  });
+
+  it("OWP-03 treats an empty answer, n, and no as no", async () => {
+    const choices = mockReadline([""], ["n"], [" no "]);
+
+    await expect(askWorktree()).resolves.toBe(false);
+    await expect(askWorktree()).resolves.toBe(false);
+    await expect(askWorktree()).resolves.toBe(false);
+
+    expect(choices.map((choice) => choice.prompts)).toEqual([
+      ["Open in a worktree? [y/N]: "],
+      ["Open in a worktree? [y/N]: "],
+      ["Open in a worktree? [y/N]: "],
+    ]);
+  });
+
+  it("OWP-04 reports invalid answers to stderr and asks again", async () => {
+    const [choice] = mockReadline(["maybe", "YeS"]);
+    const stderrWrite = vi.spyOn(process.stderr, "write").mockReturnValue(true);
+
+    await expect(askWorktree()).resolves.toBe(true);
+
+    expect(choice.prompts).toEqual([
+      "Open in a worktree? [y/N]: ",
+      "Open in a worktree? [y/N]: ",
+    ]);
+    expect(stderrWrite).toHaveBeenCalledWith("Answer y or n.\n");
+  });
+
+  it("OWP-05 rejects on EOF before starting the daemon or adopting a session", async () => {
+    mockReadline(["close"]);
+    vi.spyOn(setupCommands, "isInteractiveTerminal").mockReturnValue(true);
+    vi.spyOn(repository, "getGitInfo").mockResolvedValue({
+      root: "/repo",
+      head: "abc",
+      branch: "main",
+      isDirty: false,
+    });
+
+    await expect(runOpen(["reviewer", "--no-theme"])).rejects.toThrow(
+      "Worktree selection was interrupted; nothing was launched.",
+    );
+    expect(IpcClient.prototype.ensureDaemonStarted).not.toHaveBeenCalled();
+    expect(IpcClient.prototype.request).not.toHaveBeenCalled();
+  });
+
+  it("OWP-06 skips the question and enables an explicit worktree flag", async () => {
+    vi.spyOn(repository, "getGitInfo");
+    const ask = vi.fn();
+
+    await expect(
+      resolveOpenWorktree(true, { interactive: true, cwd: "/repo" }, ask),
+    ).resolves.toBe(true);
+
+    expect(ask).not.toHaveBeenCalled();
+    expect(repository.getGitInfo).not.toHaveBeenCalled();
+  });
+
+  it("OWP-07 accepts --no-worktree and skips the question", async () => {
+    const program = new Command();
+    program.exitOverride();
+    registerOpenCommand(program);
+    const command = program.commands.find((candidate) => candidate.name() === "open");
+    if (!command) throw new Error("open command was not registered");
+    expect(scanOptions(["--no-worktree"], command)).toEqual([]);
+
+    vi.spyOn(setupCommands, "isInteractiveTerminal").mockReturnValue(true);
+    createInterfaceMock.mockClear();
+    const create = vi.spyOn(worktree, "createWorktree");
+    const cwd = process.cwd();
+
+    await runOpen(["reviewer", "--no-theme", "--no-worktree"]);
+
+    expect(createInterfaceMock).not.toHaveBeenCalled();
+    expect(create).not.toHaveBeenCalled();
+    const [, , spawnOptions] = vi.mocked(runtime.spawnHarness).mock.calls[0];
+    expect(spawnOptions.cwd).toBe(cwd);
+  });
+
+  it("OWP-08 skips the question without a TTY or for a print launch", async () => {
+    const choices = mockReadline();
+    const terminal = vi.spyOn(setupCommands, "isInteractiveTerminal").mockReturnValue(false);
+    const create = vi.spyOn(worktree, "createWorktree").mockResolvedValue({ path: "/wt" });
+    await runOpen(["reviewer", "--no-theme"]);
+    expect(createInterfaceMock).not.toHaveBeenCalled();
+
+    terminal.mockReturnValue(true);
+    await runOpen(["reviewer", "--no-theme", "--", "--print"]);
+
+    expect(createInterfaceMock).not.toHaveBeenCalled();
+    expect(choices).toEqual([]);
+    expect(create).not.toHaveBeenCalled();
+  });
+
+  it("OWP-09 skips the question outside a git repository", async () => {
+    vi.spyOn(repository, "getGitInfo").mockResolvedValue(null);
+    const ask = vi.fn();
+
+    await expect(
+      resolveOpenWorktree(undefined, { interactive: true, cwd: "/outside" }, ask),
+    ).resolves.toBe(false);
+
+    expect(repository.getGitInfo).toHaveBeenCalledWith("/outside");
+    expect(ask).not.toHaveBeenCalled();
+  });
+
+  it("OWP-10 skips the question for a resumed session without a worktree flag", async () => {
+    vi.spyOn(repository, "getGitInfo").mockResolvedValue({
+      root: "/repo",
+      head: "abc",
+      branch: "main",
+      isDirty: false,
+    });
+    const ask = vi.fn().mockResolvedValue(true);
+
+    await expect(
+      resolveOpenWorktree(undefined, {
+        interactive: true,
+        resume: "native-session-id",
+        cwd: "/repo",
+      }, ask),
+    ).resolves.toBe(false);
+
+    expect(ask).not.toHaveBeenCalled();
+    expect(repository.getGitInfo).not.toHaveBeenCalled();
+  });
+});