🤖 feat: add isolation:none for non-local sub-agent tasks

[ammar-agent]

Summary

Adds an isolation: none | fork configuration to the task tool so sub-agents on non-local runtimes (worktree/SSH) can run directly in the parent workspace's checkout instead of paying for a fork. fork remains the default to preserve current semantics. The parameter is runtime-conditional: on local runtimes it is omitted from the tool schema entirely, so it never enters LLM context.

Background

On worktree/SSH runtimes, every spawned sub-agent forks a new checkout (git worktree / remote clone) plus runs init hooks. For read-only analysis (e.g. explore) — or when the caller has already arranged isolation via the prompt — that overhead is pure waste. Local runtimes already share the project directory, so forking is a no-op there and the option is meaningless (hence hidden).

Implementation

• Runtime-conditional tool schema (the novel part). createTaskTool now builds its inputSchema per runtime: buildTaskToolAgentArgsSchema({ includeIsolation }). isolation is only included for runtimes that support sharing the parent checkout (runtimeModeSupportsSharedTaskWorkspace → worktree/SSH). The local schema is .strict() without the field, so the model is never shown it. The canonical schema (with isolation) is still used for the execute() re-parse and token counting.
• No-fork path in TaskService.create. When isolation: "none" is honored, the task skips orchestrateFork, points its workspace path at the parent's checkout, reuses the parent runtime, and skips runBackgroundInit (the parent dir is already initialized). The queued + dequeue paths persist/honor the same flag (taskIsolation), and the dequeue fork-fallback (parent checkout gone) clears the flag.
• Deletion safety. A new taskIsolation field is persisted on the workspace config entry. WorkspaceService.remove skips physical runtime deletion for taskIsolation: "none" tasks so removing a shared task never deletes the parent's working tree. (Deletion is already keyed on the task's unique name — a no-op for shared tasks — but the guard makes the invariant explicit and future-proof.)
• Scope. Honored for worktree and ssh (the runtimes named in the request). docker/devcontainer tie runtime identity to the workspace name in the runtime factory, so they are intentionally excluded for now; multi-project parents also fall back to forking.

Validation

• make static-check green (incl. regenerated docs/hooks/tools.mdx + built-in skill snapshot from the new tool param).
• New tests: schema is runtime-conditional (task.test.ts asserts the advertised schema rejects/accepts isolation per runtime; toolDefinitions.test.ts covers the builder + description gating; runtime.test.ts covers the gating helper), isolation is forwarded to TaskService.create, an integration test that isolation: "none" shares the parent worktree without calling orchestrateFork/runBackgroundInit, and a guard test that remove never deletes the shared parent checkout.

Risks

• Touches the hot TaskService.create path (immediate + queued + dequeue) and WorkspaceService.remove. The shared path is gated behind an opt-in flag and supported runtimes; default fork behavior is unchanged. Main regression surface is task lifecycle (create/remove) on worktree/SSH — covered by the full taskService/workspaceService suites.

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[ammar-agent]

@codex review

[chatgpt-codex-connector]

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Reviewed commit: 0f4c7f284b

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[ammar-agent]

@codex review

Addressed the P1 (worktree shared-checkout resolution):

WorktreeRuntime now honors an explicit workspacePath override (mirroring SSHRuntime.getWorkspacePath). For an isolation: "none" task, the runtime is built with the child's unique name but the parent's persisted checkout path, so getWorkspacePath / ensureReady / cwd resolution all land in the parent checkout instead of the name-derived directory that was never created. Added WorktreeRuntime.test.ts covering the override + ensureReady. (SSH already honored the override via its identity-keyed getWorkspacePath.)

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. You're on a roll.

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