feat(server): add Codex thread start MCP tool

[D3OXY]

Summary

Adds a provider-scoped MCP tool, t3_thread_start, that lets Codex start another T3 Code thread only when the user explicitly asks to start, spawn, or create another thread/agent.

This keeps the tool available for intentional multi-thread workflows without encouraging autonomous delegation or background parallel work.

What changed

• Registers a new thread MCP toolkit with t3_thread_start.
• Adds a thread-management MCP capability and grants it to provider-scoped MCP sessions.
• Supports three start modes:
  • new_worktree: creates a temporary branch/worktree from the default branch by default.
  • existing_worktree: starts a thread in a supplied worktree path.
  • current_checkout: starts a thread on the current checkout and returns warning metadata.
• Inherits model/runtime/interaction settings from the source thread unless the tool call overrides them.
• Updates Codex developer instructions so this tool is used only after explicit user intent, not for autonomous delegation.

Implementation notes

• Extracts bootstrap turn-start handling from the WebSocket route into BootstrapTurnStartDispatcher.
• The shared dispatcher owns thread creation, optional worktree preparation, setup-script launch, cleanup on bootstrap failure, and VCS status refresh.
• WebSocket dispatch and MCP tool dispatch now share the same bootstrap path instead of duplicating orchestration/worktree behavior.
• MCP route registration stays lightweight; runtime-only services are registered for the server lifetime so tool registration does not leak git/projection/orchestration dependencies into HTTP route construction.

Validation

• vp check
• vp run typecheck

Risk

Moderate. This touches thread-start orchestration and WebSocket bootstrap routing, but the behavior is centralized behind the same command shape and covered with new thread-tool tests plus existing server type coverage.

Note

Add t3_thread_start MCP tool for starting Codex child threads

• Adds a new t3_thread_start MCP tool defined in tools.ts supporting new_worktree, existing_worktree, and current_checkout modes with structured input/output schemas.
• Implements handlers.ts that resolves branches/worktrees, gates on the new thread-management capability, and enqueues a thread.turn.start command via ServerRuntimeStartup.
• Extracts WebSocket bootstrap logic from ws.ts into a new BootstrapTurnStartDispatcher service in BootstrapTurnStartDispatcher.ts, which handles worktree creation, setup scripts, and VCS status refresh.
• Newly issued MCP sessions now include thread-management alongside preview in their capabilities set.
• Adds T3_CODE_THREAD_TOOL_INSTRUCTIONS to Codex developer instruction strings to guide LLM usage of the new tool.

^{Macroscope summarized 0c5c105.}

---

Note

Medium Risk
Touches thread creation, git worktrees, and orchestration on a shared bootstrap path used by WebSocket and MCP; behavior is covered by new MCP thread tests but mistakes could affect existing thread-start flows.

Overview
Adds t3_thread_start on the T3 Code MCP server so Codex can spawn child threads when the user explicitly asks. Issued provider MCP tokens now include thread-management alongside preview. The tool builds a bootstrap thread.turn.start command (default new_worktree, or existing_worktree / current_checkout), inherits settings from the invoking thread unless overridden, queues it through server startup, and returns launch metadata without waiting for the child turn.

Bootstrap turn-start logic is extracted from ws.ts into BootstrapTurnStartDispatcher (thread create, optional worktree prep, setup script, failure cleanup, VCS refresh). WebSocket bootstrap dispatch and the MCP handler both call dispatchActive.

Codex developer instructions now describe when t3_thread_start is allowed (explicit user intent, not autonomous delegation). Server startup registers the thread MCP toolkit and active bootstrap/thread-start runtimes via ServerApplicationRegistrationsLive.

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new MCP tool that allows spawning new threads/agents, representing significant new user-facing functionality and orchestration capabilities that warrant human review.

^{You can customize Macroscope's approvability policy. Learn more.}

[D3OXY]

#2829

[juliusmarminge]

we can get this in before #2829 :)

[D3OXY]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Configure here.}

[macroscopeapp]

Effect Service Conventions: 2 findings on the newly added thread-spawn services. See inline comments.

^{Posted via Macroscope — Effect Service Conventions}

[D3OXY]

@juliusmarminge

[macroscopeapp]

One Effect convention issue: several ThreadStartToolError constructions derive message from cause.message, which the error conventions prohibit. The wrapper message must come from the error's own structural attributes (e.g. operation/cwd), never from cause/cause.message; the underlying failure is already preserved in cause. This applies to handlers.ts lines 97, 199, 222, 309 (the cause instanceof Error ? cause.message : ... branches) and line 360 (message: cause.message). Each site already has a static fallback string (or can derive one from operation), so drop the cause.message branch and keep cause for the full chain.

^{Posted via Macroscope — Effect Service Conventions}

[juliusmarminge]

Changed my mind. Gonna push to get the new orchestrator soon out which has more powerful capabilities

[D3OXY]

Summary

Adds a provider-scoped MCP tool, t3_thread_start, that lets Codex start another T3 Code thread only when the user explicitly asks to start, spawn, or create another thread/agent.

This keeps the tool available for intentional multi-thread workflows without encouraging autonomous delegation or background parallel work.

What changed

• Registers a new thread MCP toolkit with t3_thread_start.
• Adds a thread-management MCP capability and grants it to provider-scoped MCP sessions.
• Supports three start modes:
  • new_worktree: creates a temporary branch/worktree from the default branch by default.
  • existing_worktree: starts a thread in a supplied worktree path.
  • current_checkout: starts a thread on the current checkout and returns warning metadata.
• Inherits model/runtime/interaction settings from the source thread unless the tool call overrides them.
• Updates Codex developer instructions so this tool is used only after explicit user intent, not for autonomous delegation.

Implementation notes

• Extracts bootstrap turn-start handling from the WebSocket route into BootstrapTurnStartDispatcher.
• The shared dispatcher owns thread creation, optional worktree preparation, setup-script launch, cleanup on bootstrap failure, and VCS status refresh.
• WebSocket dispatch and MCP tool dispatch now share the same bootstrap path instead of duplicating orchestration/worktree behavior.
• MCP route registration stays lightweight; runtime-only services are registered for the server lifetime so tool registration does not leak git/projection/orchestration dependencies into HTTP route construction.

Validation

• vp check
• vp run typecheck

Risk

Moderate. This touches thread-start orchestration and WebSocket bootstrap routing, but the behavior is centralized behind the same command shape and covered with new thread-tool tests plus existing server type coverage.

Note

Add t3_thread_start MCP tool for starting Codex child threads

• Adds a new t3_thread_start MCP tool defined in tools.ts supporting new_worktree, existing_worktree, and current_checkout modes with structured input/output schemas.
• Implements handlers.ts that resolves branches/worktrees, gates on the new thread-management capability, and enqueues a thread.turn.start command via ServerRuntimeStartup.
• Extracts WebSocket bootstrap logic from ws.ts into a new BootstrapTurnStartDispatcher service in BootstrapTurnStartDispatcher.ts, which handles worktree creation, setup scripts, and VCS status refresh.
• Newly issued MCP sessions now include thread-management alongside preview in their capabilities set.
• Adds T3_CODE_THREAD_TOOL_INSTRUCTIONS to Codex developer instruction strings to guide LLM usage of the new tool.

^{Macroscope summarized 0c5c105.}

---

Note

Medium Risk
Touches thread creation, git worktrees, and orchestration on a shared bootstrap path used by WebSocket and MCP; behavior is covered by new MCP thread tests but mistakes could affect existing thread-start flows.

Overview
Adds t3_thread_start on the T3 Code MCP server so Codex can spawn child threads when the user explicitly asks. Issued provider MCP tokens now include thread-management alongside preview. The tool builds a bootstrap thread.turn.start command (default new_worktree, or existing_worktree / current_checkout), inherits settings from the invoking thread unless overridden, queues it through server startup, and returns launch metadata without waiting for the child turn.

Bootstrap turn-start logic is extracted from ws.ts into BootstrapTurnStartDispatcher (thread create, optional worktree prep, setup script, failure cleanup, VCS refresh). WebSocket bootstrap dispatch and the MCP handler both call dispatchActive.

Codex developer instructions now describe when t3_thread_start is allowed (explicit user intent, not autonomous delegation). Server startup registers the thread MCP toolkit and active bootstrap/thread-start runtimes via ServerApplicationRegistrationsLive.

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 1633dfd5-1922-41e8-b230-7e4ad7a78498

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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❤️ Share

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new MCP tool that allows spawning new threads/agents, representing significant new user-facing functionality and orchestration capabilities that warrant human review.

^{You can customize Macroscope's approvability policy. Learn more.}

[D3OXY]

#2829

[juliusmarminge]

we can get this in before #2829 :)

[D3OXY]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Configure here.}

[macroscopeapp]

Effect Service Conventions: 2 findings on the newly added thread-spawn services. See inline comments.

^{Posted via Macroscope — Effect Service Conventions}

[D3OXY]

@juliusmarminge

[macroscopeapp]

One Effect convention issue: several ThreadStartToolError constructions derive message from cause.message, which the error conventions prohibit. The wrapper message must come from the error's own structural attributes (e.g. operation/cwd), never from cause/cause.message; the underlying failure is already preserved in cause. This applies to handlers.ts lines 97, 199, 222, 309 (the cause instanceof Error ? cause.message : ... branches) and line 360 (message: cause.message). Each site already has a static fallback string (or can derive one from operation), so drop the cause.message branch and keep cause for the full chain.

^{Posted via Macroscope — Effect Service Conventions}

[juliusmarminge]

Changed my mind. Gonna push to get the new orchestrator soon out which has more powerful capabilities

[D3OXY]

Summary

Adds a provider-scoped MCP tool, t3_thread_start, that lets Codex start another T3 Code thread only when the user explicitly asks to start, spawn, or create another thread/agent.

This keeps the tool available for intentional multi-thread workflows without encouraging autonomous delegation or background parallel work.

What changed

• Registers a new thread MCP toolkit with t3_thread_start.
• Adds a thread-management MCP capability and grants it to provider-scoped MCP sessions.
• Supports three start modes:
  • new_worktree: creates a temporary branch/worktree from the default branch by default.
  • existing_worktree: starts a thread in a supplied worktree path.
  • current_checkout: starts a thread on the current checkout and returns warning metadata.
• Inherits model/runtime/interaction settings from the source thread unless the tool call overrides them.
• Updates Codex developer instructions so this tool is used only after explicit user intent, not for autonomous delegation.

Implementation notes

• Extracts bootstrap turn-start handling from the WebSocket route into BootstrapTurnStartDispatcher.
• The shared dispatcher owns thread creation, optional worktree preparation, setup-script launch, cleanup on bootstrap failure, and VCS status refresh.
• WebSocket dispatch and MCP tool dispatch now share the same bootstrap path instead of duplicating orchestration/worktree behavior.
• MCP route registration stays lightweight; runtime-only services are registered for the server lifetime so tool registration does not leak git/projection/orchestration dependencies into HTTP route construction.

Validation

• vp check
• vp run typecheck

Risk

Moderate. This touches thread-start orchestration and WebSocket bootstrap routing, but the behavior is centralized behind the same command shape and covered with new thread-tool tests plus existing server type coverage.

Note

Add t3_thread_start MCP tool for starting Codex child threads

• Adds a new t3_thread_start MCP tool defined in tools.ts supporting new_worktree, existing_worktree, and current_checkout modes with structured input/output schemas.
• Implements handlers.ts that resolves branches/worktrees, gates on the new thread-management capability, and enqueues a thread.turn.start command via ServerRuntimeStartup.
• Extracts WebSocket bootstrap logic from ws.ts into a new BootstrapTurnStartDispatcher service in BootstrapTurnStartDispatcher.ts, which handles worktree creation, setup scripts, and VCS status refresh.
• Newly issued MCP sessions now include thread-management alongside preview in their capabilities set.
• Adds T3_CODE_THREAD_TOOL_INSTRUCTIONS to Codex developer instruction strings to guide LLM usage of the new tool.

^{Macroscope summarized 0c5c105.}

---

Note

Medium Risk
Touches thread creation, git worktrees, and orchestration on a shared bootstrap path used by WebSocket and MCP; behavior is covered by new MCP thread tests but mistakes could affect existing thread-start flows.

Overview
Adds t3_thread_start on the T3 Code MCP server so Codex can spawn child threads when the user explicitly asks. Issued provider MCP tokens now include thread-management alongside preview. The tool builds a bootstrap thread.turn.start command (default new_worktree, or existing_worktree / current_checkout), inherits settings from the invoking thread unless overridden, queues it through server startup, and returns launch metadata without waiting for the child turn.

Bootstrap turn-start logic is extracted from ws.ts into BootstrapTurnStartDispatcher (thread create, optional worktree prep, setup script, failure cleanup, VCS refresh). WebSocket bootstrap dispatch and the MCP handler both call dispatchActive.

Codex developer instructions now describe when t3_thread_start is allowed (explicit user intent, not autonomous delegation). Server startup registers the thread MCP toolkit and active bootstrap/thread-start runtimes via ServerApplicationRegistrationsLive.

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 1633dfd5-1922-41e8-b230-7e4ad7a78498

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
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_{Comment @coderabbitai help to get the list of available commands.}

[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new MCP tool that allows spawning new threads/agents, representing significant new user-facing functionality and orchestration capabilities that warrant human review.

^{You can customize Macroscope's approvability policy. Learn more.}

[D3OXY]

#2829

[juliusmarminge]

we can get this in before #2829 :)

[D3OXY]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Configure here.}

[macroscopeapp]

Effect Service Conventions: 2 findings on the newly added thread-spawn services. See inline comments.

^{Posted via Macroscope — Effect Service Conventions}

[D3OXY]

@juliusmarminge

[macroscopeapp]

One Effect convention issue: several ThreadStartToolError constructions derive message from cause.message, which the error conventions prohibit. The wrapper message must come from the error's own structural attributes (e.g. operation/cwd), never from cause/cause.message; the underlying failure is already preserved in cause. This applies to handlers.ts lines 97, 199, 222, 309 (the cause instanceof Error ? cause.message : ... branches) and line 360 (message: cause.message). Each site already has a static fallback string (or can derive one from operation), so drop the cause.message branch and keep cause for the full chain.

^{Posted via Macroscope — Effect Service Conventions}

[juliusmarminge]

Changed my mind. Gonna push to get the new orchestrator soon out which has more powerful capabilities

[D3OXY]

Summary

Adds a provider-scoped MCP tool, t3_thread_start, that lets Codex start another T3 Code thread only when the user explicitly asks to start, spawn, or create another thread/agent.

This keeps the tool available for intentional multi-thread workflows without encouraging autonomous delegation or background parallel work.

What changed

• Registers a new thread MCP toolkit with t3_thread_start.
• Adds a thread-management MCP capability and grants it to provider-scoped MCP sessions.
• Supports three start modes:
  • new_worktree: creates a temporary branch/worktree from the default branch by default.
  • existing_worktree: starts a thread in a supplied worktree path.
  • current_checkout: starts a thread on the current checkout and returns warning metadata.
• Inherits model/runtime/interaction settings from the source thread unless the tool call overrides them.
• Updates Codex developer instructions so this tool is used only after explicit user intent, not for autonomous delegation.

Implementation notes

• Extracts bootstrap turn-start handling from the WebSocket route into BootstrapTurnStartDispatcher.
• The shared dispatcher owns thread creation, optional worktree preparation, setup-script launch, cleanup on bootstrap failure, and VCS status refresh.
• WebSocket dispatch and MCP tool dispatch now share the same bootstrap path instead of duplicating orchestration/worktree behavior.
• MCP route registration stays lightweight; runtime-only services are registered for the server lifetime so tool registration does not leak git/projection/orchestration dependencies into HTTP route construction.

Validation

• vp check
• vp run typecheck

Risk

Moderate. This touches thread-start orchestration and WebSocket bootstrap routing, but the behavior is centralized behind the same command shape and covered with new thread-tool tests plus existing server type coverage.

Note

Add t3_thread_start MCP tool for starting Codex child threads

• Adds a new t3_thread_start MCP tool defined in tools.ts supporting new_worktree, existing_worktree, and current_checkout modes with structured input/output schemas.
• Implements handlers.ts that resolves branches/worktrees, gates on the new thread-management capability, and enqueues a thread.turn.start command via ServerRuntimeStartup.
• Extracts WebSocket bootstrap logic from ws.ts into a new BootstrapTurnStartDispatcher service in BootstrapTurnStartDispatcher.ts, which handles worktree creation, setup scripts, and VCS status refresh.
• Newly issued MCP sessions now include thread-management alongside preview in their capabilities set.
• Adds T3_CODE_THREAD_TOOL_INSTRUCTIONS to Codex developer instruction strings to guide LLM usage of the new tool.

^{Macroscope summarized 0c5c105.}

---

Note

Medium Risk
Touches thread creation, git worktrees, and orchestration on a shared bootstrap path used by WebSocket and MCP; behavior is covered by new MCP thread tests but mistakes could affect existing thread-start flows.

Overview
Adds t3_thread_start on the T3 Code MCP server so Codex can spawn child threads when the user explicitly asks. Issued provider MCP tokens now include thread-management alongside preview. The tool builds a bootstrap thread.turn.start command (default new_worktree, or existing_worktree / current_checkout), inherits settings from the invoking thread unless overridden, queues it through server startup, and returns launch metadata without waiting for the child turn.

Bootstrap turn-start logic is extracted from ws.ts into BootstrapTurnStartDispatcher (thread create, optional worktree prep, setup script, failure cleanup, VCS refresh). WebSocket bootstrap dispatch and the MCP handler both call dispatchActive.

Codex developer instructions now describe when t3_thread_start is allowed (explicit user intent, not autonomous delegation). Server startup registers the thread MCP toolkit and active bootstrap/thread-start runtimes via ServerApplicationRegistrationsLive.

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 1633dfd5-1922-41e8-b230-7e4ad7a78498

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

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• Mastodon
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_{Comment @coderabbitai help to get the list of available commands.}

[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new MCP tool that allows spawning new threads/agents, representing significant new user-facing functionality and orchestration capabilities that warrant human review.

^{You can customize Macroscope's approvability policy. Learn more.}

[D3OXY]

#2829

[juliusmarminge]

we can get this in before #2829 :)

[D3OXY]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Configure here.}

[macroscopeapp]

Effect Service Conventions: 2 findings on the newly added thread-spawn services. See inline comments.

^{Posted via Macroscope — Effect Service Conventions}

[D3OXY]

@juliusmarminge

[macroscopeapp]

One Effect convention issue: several ThreadStartToolError constructions derive message from cause.message, which the error conventions prohibit. The wrapper message must come from the error's own structural attributes (e.g. operation/cwd), never from cause/cause.message; the underlying failure is already preserved in cause. This applies to handlers.ts lines 97, 199, 222, 309 (the cause instanceof Error ? cause.message : ... branches) and line 360 (message: cause.message). Each site already has a static fallback string (or can derive one from operation), so drop the cause.message branch and keep cause for the full chain.

^{Posted via Macroscope — Effect Service Conventions}

[juliusmarminge]

Changed my mind. Gonna push to get the new orchestrator soon out which has more powerful capabilities

[D3OXY]

Summary

Adds a provider-scoped MCP tool, t3_thread_start, that lets Codex start another T3 Code thread only when the user explicitly asks to start, spawn, or create another thread/agent.

This keeps the tool available for intentional multi-thread workflows without encouraging autonomous delegation or background parallel work.

What changed

• Registers a new thread MCP toolkit with t3_thread_start.
• Adds a thread-management MCP capability and grants it to provider-scoped MCP sessions.
• Supports three start modes:
  • new_worktree: creates a temporary branch/worktree from the default branch by default.
  • existing_worktree: starts a thread in a supplied worktree path.
  • current_checkout: starts a thread on the current checkout and returns warning metadata.
• Inherits model/runtime/interaction settings from the source thread unless the tool call overrides them.
• Updates Codex developer instructions so this tool is used only after explicit user intent, not for autonomous delegation.

Implementation notes

• Extracts bootstrap turn-start handling from the WebSocket route into BootstrapTurnStartDispatcher.
• The shared dispatcher owns thread creation, optional worktree preparation, setup-script launch, cleanup on bootstrap failure, and VCS status refresh.
• WebSocket dispatch and MCP tool dispatch now share the same bootstrap path instead of duplicating orchestration/worktree behavior.
• MCP route registration stays lightweight; runtime-only services are registered for the server lifetime so tool registration does not leak git/projection/orchestration dependencies into HTTP route construction.

Validation

• vp check
• vp run typecheck

Risk

Moderate. This touches thread-start orchestration and WebSocket bootstrap routing, but the behavior is centralized behind the same command shape and covered with new thread-tool tests plus existing server type coverage.

Note

Add t3_thread_start MCP tool for starting Codex child threads

• Adds a new t3_thread_start MCP tool defined in tools.ts supporting new_worktree, existing_worktree, and current_checkout modes with structured input/output schemas.
• Implements handlers.ts that resolves branches/worktrees, gates on the new thread-management capability, and enqueues a thread.turn.start command via ServerRuntimeStartup.
• Extracts WebSocket bootstrap logic from ws.ts into a new BootstrapTurnStartDispatcher service in BootstrapTurnStartDispatcher.ts, which handles worktree creation, setup scripts, and VCS status refresh.
• Newly issued MCP sessions now include thread-management alongside preview in their capabilities set.
• Adds T3_CODE_THREAD_TOOL_INSTRUCTIONS to Codex developer instruction strings to guide LLM usage of the new tool.

^{Macroscope summarized 0c5c105.}

---

Note

Medium Risk
Touches thread creation, git worktrees, and orchestration on a shared bootstrap path used by WebSocket and MCP; behavior is covered by new MCP thread tests but mistakes could affect existing thread-start flows.

Overview
Adds t3_thread_start on the T3 Code MCP server so Codex can spawn child threads when the user explicitly asks. Issued provider MCP tokens now include thread-management alongside preview. The tool builds a bootstrap thread.turn.start command (default new_worktree, or existing_worktree / current_checkout), inherits settings from the invoking thread unless overridden, queues it through server startup, and returns launch metadata without waiting for the child turn.

Bootstrap turn-start logic is extracted from ws.ts into BootstrapTurnStartDispatcher (thread create, optional worktree prep, setup script, failure cleanup, VCS refresh). WebSocket bootstrap dispatch and the MCP handler both call dispatchActive.

Codex developer instructions now describe when t3_thread_start is allowed (explicit user intent, not autonomous delegation). Server startup registers the thread MCP toolkit and active bootstrap/thread-start runtimes via ServerApplicationRegistrationsLive.

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 1633dfd5-1922-41e8-b230-7e4ad7a78498

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new MCP tool that allows spawning new threads/agents, representing significant new user-facing functionality and orchestration capabilities that warrant human review.

^{You can customize Macroscope's approvability policy. Learn more.}

[D3OXY]

#2829

[juliusmarminge]

we can get this in before #2829 :)

[D3OXY]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Configure here.}

[macroscopeapp]

Effect Service Conventions: 2 findings on the newly added thread-spawn services. See inline comments.

^{Posted via Macroscope — Effect Service Conventions}

[D3OXY]

@juliusmarminge

[macroscopeapp]

One Effect convention issue: several ThreadStartToolError constructions derive message from cause.message, which the error conventions prohibit. The wrapper message must come from the error's own structural attributes (e.g. operation/cwd), never from cause/cause.message; the underlying failure is already preserved in cause. This applies to handlers.ts lines 97, 199, 222, 309 (the cause instanceof Error ? cause.message : ... branches) and line 360 (message: cause.message). Each site already has a static fallback string (or can derive one from operation), so drop the cause.message branch and keep cause for the full chain.

^{Posted via Macroscope — Effect Service Conventions}

[juliusmarminge]

Changed my mind. Gonna push to get the new orchestrator soon out which has more powerful capabilities

[D3OXY]

Summary

Adds a provider-scoped MCP tool, t3_thread_start, that lets Codex start another T3 Code thread only when the user explicitly asks to start, spawn, or create another thread/agent.

This keeps the tool available for intentional multi-thread workflows without encouraging autonomous delegation or background parallel work.

What changed

• Registers a new thread MCP toolkit with t3_thread_start.
• Adds a thread-management MCP capability and grants it to provider-scoped MCP sessions.
• Supports three start modes:
  • new_worktree: creates a temporary branch/worktree from the default branch by default.
  • existing_worktree: starts a thread in a supplied worktree path.
  • current_checkout: starts a thread on the current checkout and returns warning metadata.
• Inherits model/runtime/interaction settings from the source thread unless the tool call overrides them.
• Updates Codex developer instructions so this tool is used only after explicit user intent, not for autonomous delegation.

Implementation notes

• Extracts bootstrap turn-start handling from the WebSocket route into BootstrapTurnStartDispatcher.
• The shared dispatcher owns thread creation, optional worktree preparation, setup-script launch, cleanup on bootstrap failure, and VCS status refresh.
• WebSocket dispatch and MCP tool dispatch now share the same bootstrap path instead of duplicating orchestration/worktree behavior.
• MCP route registration stays lightweight; runtime-only services are registered for the server lifetime so tool registration does not leak git/projection/orchestration dependencies into HTTP route construction.

Validation

• vp check
• vp run typecheck

Risk

Moderate. This touches thread-start orchestration and WebSocket bootstrap routing, but the behavior is centralized behind the same command shape and covered with new thread-tool tests plus existing server type coverage.

Note

Add t3_thread_start MCP tool for starting Codex child threads

• Adds a new t3_thread_start MCP tool defined in tools.ts supporting new_worktree, existing_worktree, and current_checkout modes with structured input/output schemas.
• Implements handlers.ts that resolves branches/worktrees, gates on the new thread-management capability, and enqueues a thread.turn.start command via ServerRuntimeStartup.
• Extracts WebSocket bootstrap logic from ws.ts into a new BootstrapTurnStartDispatcher service in BootstrapTurnStartDispatcher.ts, which handles worktree creation, setup scripts, and VCS status refresh.
• Newly issued MCP sessions now include thread-management alongside preview in their capabilities set.
• Adds T3_CODE_THREAD_TOOL_INSTRUCTIONS to Codex developer instruction strings to guide LLM usage of the new tool.

^{Macroscope summarized 0c5c105.}

---

Note

Medium Risk
Touches thread creation, git worktrees, and orchestration on a shared bootstrap path used by WebSocket and MCP; behavior is covered by new MCP thread tests but mistakes could affect existing thread-start flows.

Overview
Adds t3_thread_start on the T3 Code MCP server so Codex can spawn child threads when the user explicitly asks. Issued provider MCP tokens now include thread-management alongside preview. The tool builds a bootstrap thread.turn.start command (default new_worktree, or existing_worktree / current_checkout), inherits settings from the invoking thread unless overridden, queues it through server startup, and returns launch metadata without waiting for the child turn.

Bootstrap turn-start logic is extracted from ws.ts into BootstrapTurnStartDispatcher (thread create, optional worktree prep, setup script, failure cleanup, VCS refresh). WebSocket bootstrap dispatch and the MCP handler both call dispatchActive.

Codex developer instructions now describe when t3_thread_start is allowed (explicit user intent, not autonomous delegation). Server startup registers the thread MCP toolkit and active bootstrap/thread-start runtimes via ServerApplicationRegistrationsLive.

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

Important

Review skipped

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new MCP tool that allows spawning new threads/agents, representing significant new user-facing functionality and orchestration capabilities that warrant human review.

^{You can customize Macroscope's approvability policy. Learn more.}

[D3OXY]

#2829

[juliusmarminge]

we can get this in before #2829 :)

[D3OXY]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Configure here.}

[macroscopeapp]

Effect Service Conventions: 2 findings on the newly added thread-spawn services. See inline comments.

^{Posted via Macroscope — Effect Service Conventions}

[D3OXY]

@juliusmarminge

[macroscopeapp]

One Effect convention issue: several ThreadStartToolError constructions derive message from cause.message, which the error conventions prohibit. The wrapper message must come from the error's own structural attributes (e.g. operation/cwd), never from cause/cause.message; the underlying failure is already preserved in cause. This applies to handlers.ts lines 97, 199, 222, 309 (the cause instanceof Error ? cause.message : ... branches) and line 360 (message: cause.message). Each site already has a static fallback string (or can derive one from operation), so drop the cause.message branch and keep cause for the full chain.

^{Posted via Macroscope — Effect Service Conventions}

[juliusmarminge]

Changed my mind. Gonna push to get the new orchestrator soon out which has more powerful capabilities

[D3OXY]

Summary

Adds a provider-scoped MCP tool, t3_thread_start, that lets Codex start another T3 Code thread only when the user explicitly asks to start, spawn, or create another thread/agent.

This keeps the tool available for intentional multi-thread workflows without encouraging autonomous delegation or background parallel work.

What changed

• Registers a new thread MCP toolkit with t3_thread_start.
• Adds a thread-management MCP capability and grants it to provider-scoped MCP sessions.
• Supports three start modes:
  • new_worktree: creates a temporary branch/worktree from the default branch by default.
  • existing_worktree: starts a thread in a supplied worktree path.
  • current_checkout: starts a thread on the current checkout and returns warning metadata.
• Inherits model/runtime/interaction settings from the source thread unless the tool call overrides them.
• Updates Codex developer instructions so this tool is used only after explicit user intent, not for autonomous delegation.

Implementation notes

• Extracts bootstrap turn-start handling from the WebSocket route into BootstrapTurnStartDispatcher.
• The shared dispatcher owns thread creation, optional worktree preparation, setup-script launch, cleanup on bootstrap failure, and VCS status refresh.
• WebSocket dispatch and MCP tool dispatch now share the same bootstrap path instead of duplicating orchestration/worktree behavior.
• MCP route registration stays lightweight; runtime-only services are registered for the server lifetime so tool registration does not leak git/projection/orchestration dependencies into HTTP route construction.

Validation

• vp check
• vp run typecheck

Risk

Moderate. This touches thread-start orchestration and WebSocket bootstrap routing, but the behavior is centralized behind the same command shape and covered with new thread-tool tests plus existing server type coverage.

Note

Add t3_thread_start MCP tool for starting Codex child threads

• Adds a new t3_thread_start MCP tool defined in tools.ts supporting new_worktree, existing_worktree, and current_checkout modes with structured input/output schemas.
• Implements handlers.ts that resolves branches/worktrees, gates on the new thread-management capability, and enqueues a thread.turn.start command via ServerRuntimeStartup.
• Extracts WebSocket bootstrap logic from ws.ts into a new BootstrapTurnStartDispatcher service in BootstrapTurnStartDispatcher.ts, which handles worktree creation, setup scripts, and VCS status refresh.
• Newly issued MCP sessions now include thread-management alongside preview in their capabilities set.
• Adds T3_CODE_THREAD_TOOL_INSTRUCTIONS to Codex developer instruction strings to guide LLM usage of the new tool.

^{Macroscope summarized 0c5c105.}

---

Note

Medium Risk
Touches thread creation, git worktrees, and orchestration on a shared bootstrap path used by WebSocket and MCP; behavior is covered by new MCP thread tests but mistakes could affect existing thread-start flows.

Overview
Adds t3_thread_start on the T3 Code MCP server so Codex can spawn child threads when the user explicitly asks. Issued provider MCP tokens now include thread-management alongside preview. The tool builds a bootstrap thread.turn.start command (default new_worktree, or existing_worktree / current_checkout), inherits settings from the invoking thread unless overridden, queues it through server startup, and returns launch metadata without waiting for the child turn.

Bootstrap turn-start logic is extracted from ws.ts into BootstrapTurnStartDispatcher (thread create, optional worktree prep, setup script, failure cleanup, VCS refresh). WebSocket bootstrap dispatch and the MCP handler both call dispatchActive.

Codex developer instructions now describe when t3_thread_start is allowed (explicit user intent, not autonomous delegation). Server startup registers the thread MCP toolkit and active bootstrap/thread-start runtimes via ServerApplicationRegistrationsLive.

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 1633dfd5-1922-41e8-b230-7e4ad7a78498

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

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• Mastodon
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_{Comment @coderabbitai help to get the list of available commands.}

[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new MCP tool that allows spawning new threads/agents, representing significant new user-facing functionality and orchestration capabilities that warrant human review.

^{You can customize Macroscope's approvability policy. Learn more.}

[D3OXY]

#2829

[juliusmarminge]

we can get this in before #2829 :)

[D3OXY]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Configure here.}

[macroscopeapp]

Effect Service Conventions: 2 findings on the newly added thread-spawn services. See inline comments.

^{Posted via Macroscope — Effect Service Conventions}

[D3OXY]

@juliusmarminge

[macroscopeapp]

One Effect convention issue: several ThreadStartToolError constructions derive message from cause.message, which the error conventions prohibit. The wrapper message must come from the error's own structural attributes (e.g. operation/cwd), never from cause/cause.message; the underlying failure is already preserved in cause. This applies to handlers.ts lines 97, 199, 222, 309 (the cause instanceof Error ? cause.message : ... branches) and line 360 (message: cause.message). Each site already has a static fallback string (or can derive one from operation), so drop the cause.message branch and keep cause for the full chain.

^{Posted via Macroscope — Effect Service Conventions}

[juliusmarminge]

Changed my mind. Gonna push to get the new orchestrator soon out which has more powerful capabilities

[D3OXY]

Summary

Adds a provider-scoped MCP tool, t3_thread_start, that lets Codex start another T3 Code thread only when the user explicitly asks to start, spawn, or create another thread/agent.

This keeps the tool available for intentional multi-thread workflows without encouraging autonomous delegation or background parallel work.

What changed

• Registers a new thread MCP toolkit with t3_thread_start.
• Adds a thread-management MCP capability and grants it to provider-scoped MCP sessions.
• Supports three start modes:
  • new_worktree: creates a temporary branch/worktree from the default branch by default.
  • existing_worktree: starts a thread in a supplied worktree path.
  • current_checkout: starts a thread on the current checkout and returns warning metadata.
• Inherits model/runtime/interaction settings from the source thread unless the tool call overrides them.
• Updates Codex developer instructions so this tool is used only after explicit user intent, not for autonomous delegation.

Implementation notes

• Extracts bootstrap turn-start handling from the WebSocket route into BootstrapTurnStartDispatcher.
• The shared dispatcher owns thread creation, optional worktree preparation, setup-script launch, cleanup on bootstrap failure, and VCS status refresh.
• WebSocket dispatch and MCP tool dispatch now share the same bootstrap path instead of duplicating orchestration/worktree behavior.
• MCP route registration stays lightweight; runtime-only services are registered for the server lifetime so tool registration does not leak git/projection/orchestration dependencies into HTTP route construction.

Validation

• vp check
• vp run typecheck

Risk

Moderate. This touches thread-start orchestration and WebSocket bootstrap routing, but the behavior is centralized behind the same command shape and covered with new thread-tool tests plus existing server type coverage.

Note

Add t3_thread_start MCP tool for starting Codex child threads

• Adds a new t3_thread_start MCP tool defined in tools.ts supporting new_worktree, existing_worktree, and current_checkout modes with structured input/output schemas.
• Implements handlers.ts that resolves branches/worktrees, gates on the new thread-management capability, and enqueues a thread.turn.start command via ServerRuntimeStartup.
• Extracts WebSocket bootstrap logic from ws.ts into a new BootstrapTurnStartDispatcher service in BootstrapTurnStartDispatcher.ts, which handles worktree creation, setup scripts, and VCS status refresh.
• Newly issued MCP sessions now include thread-management alongside preview in their capabilities set.
• Adds T3_CODE_THREAD_TOOL_INSTRUCTIONS to Codex developer instruction strings to guide LLM usage of the new tool.

^{Macroscope summarized 0c5c105.}

---

Note

Medium Risk
Touches thread creation, git worktrees, and orchestration on a shared bootstrap path used by WebSocket and MCP; behavior is covered by new MCP thread tests but mistakes could affect existing thread-start flows.

Overview
Adds t3_thread_start on the T3 Code MCP server so Codex can spawn child threads when the user explicitly asks. Issued provider MCP tokens now include thread-management alongside preview. The tool builds a bootstrap thread.turn.start command (default new_worktree, or existing_worktree / current_checkout), inherits settings from the invoking thread unless overridden, queues it through server startup, and returns launch metadata without waiting for the child turn.

Bootstrap turn-start logic is extracted from ws.ts into BootstrapTurnStartDispatcher (thread create, optional worktree prep, setup script, failure cleanup, VCS refresh). WebSocket bootstrap dispatch and the MCP handler both call dispatchActive.

Codex developer instructions now describe when t3_thread_start is allowed (explicit user intent, not autonomous delegation). Server startup registers the thread MCP toolkit and active bootstrap/thread-start runtimes via ServerApplicationRegistrationsLive.

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 1633dfd5-1922-41e8-b230-7e4ad7a78498

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new MCP tool that allows spawning new threads/agents, representing significant new user-facing functionality and orchestration capabilities that warrant human review.

^{You can customize Macroscope's approvability policy. Learn more.}

[D3OXY]

#2829

[juliusmarminge]

we can get this in before #2829 :)

[D3OXY]

@cursor review

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 094c88c9546f759de560c041b4bb3f323195511e. Configure here.}

[macroscopeapp]

Effect Service Conventions: 2 findings on the newly added thread-spawn services. See inline comments.

^{Posted via Macroscope — Effect Service Conventions}

[D3OXY]

@juliusmarminge

[macroscopeapp]

One Effect convention issue: several ThreadStartToolError constructions derive message from cause.message, which the error conventions prohibit. The wrapper message must come from the error's own structural attributes (e.g. operation/cwd), never from cause/cause.message; the underlying failure is already preserved in cause. This applies to handlers.ts lines 97, 199, 222, 309 (the cause instanceof Error ? cause.message : ... branches) and line 360 (message: cause.message). Each site already has a static fallback string (or can derive one from operation), so drop the cause.message branch and keep cause for the full chain.

^{Posted via Macroscope — Effect Service Conventions}

[juliusmarminge]

Changed my mind. Gonna push to get the new orchestrator soon out which has more powerful capabilities