feat(mcp): add deferred thread archive tools

[pandec]

Agents asked to archive their thread when finished could miss the existing CLI command and report that no tool was available. Add archive_thread, archive_thread_status, and cancel_thread_archive to every T3 MCP endpoint, scoped to the invoking thread.

The tools reuse the existing archive workflow, wait for successful turn completion and checkpointing, and require an explicit flag for worktree removal. Responses distinguish a pending request from a completed archive. Status reads include archived threads so cleanup errors remain visible. README and user guidance describe the new tools.

Validation:

• 89 focused tests covering the MCP handlers, registration, archive reactor, and projection queries.
• vp check and vp run typecheck passed. Repository lint reports existing warnings, with no errors; targeted lint passed.
• No client launch was needed for this server-only wrapper.

Model: GPT-6-Astra. Harness: Codex in T3 Code.

Summary by CodeRabbit

• New Features
  • Agents can schedule thread archiving after completing their response and background work, check archive status, or cancel a pending request.
  • Archiving is also available through the CLI for the current thread or a specified thread, with requests preserved across restarts.
  • Cleanup can remove a thread’s worktree while preserving branches, project roots, and checkouts used by other threads.
• Documentation
  • Updated the README and CLI automation guide with archiving workflows and behavior.

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⚙️ Run configuration

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📥 Commits

Reviewing files that changed from the base of the PR and between 627d9cc and 360d45e.

📒 Files selected for processing (2)

• apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.test.ts
• apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.ts

📝 Walkthrough

Walkthrough

The server adds MCP tools to request thread archival, inspect archive status, and cancel a pending request. The handlers validate thread ownership and use snapshot queries that can include archived threads. MCP islands register the archive toolkit, and the documentation describes the workflow.

Changes

Thread archive MCP workflow

Layer / File(s)	Summary
Archived-thread snapshot lookup apps/server/src/orchestration/Services/ProjectionSnapshotQuery.ts, apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.ts, apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.test.ts	The snapshot query accepts an optional includeArchived option. Archived threads remain excluded by default. Tests cover retrieving an archived thread with the option enabled.
Archive tool contracts and handlers apps/server/src/mcp/toolkits/archive/tools.ts, apps/server/src/mcp/toolkits/archive/handlers.ts, apps/server/src/mcp/toolkits/archive/handlers.test.ts	The toolkit defines archive, status, and cancellation tools. Handlers validate thread availability and ownership, schedule archival, return status, and dispatch cancellation only for pending requests. Tests cover these behaviors and error cases.
MCP registration and usage documentation apps/server/src/mcp/McpHttpServer.ts, apps/server/src/mcp/McpHttpServer.test.ts, docs/user/cli-automation.md, README.md	MCP islands register the archive toolkit alongside the worktree toolkit. Tests cover registration and metadata. Documentation describes the archive tools and workflow.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant MCPClient
  participant ArchiveToolkitHandlersLive
  participant ProjectionSnapshotQuery
  participant OrchestrationEngine
  MCPClient->>ArchiveToolkitHandlersLive: call archive_thread
  ArchiveToolkitHandlersLive->>ProjectionSnapshotQuery: read thread including archived
  ProjectionSnapshotQuery-->>ArchiveToolkitHandlersLive: return thread snapshot
  ArchiveToolkitHandlersLive->>OrchestrationEngine: dispatch archive after current turn
  OrchestrationEngine-->>ArchiveToolkitHandlersLive: return dispatch result
  ArchiveToolkitHandlersLive-->>MCPClient: return archive status

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Suggested reviewers: juliusmarminge

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: adding deferred thread archive tools to MCP.
Description check	✅ Passed	The description explains what changed, why it changed, the workflow behavior, scope, documentation updates, and validation results. It omits the template checklist and does not use the template headin…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at
@apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.ts:
- Line 3987: Update getLatestTurnRowByThread to accept and apply the
includeArchived option, and pass the same option from getThreadShellById so
archived threads can include their latest turn.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository: pandec/t3code/.coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: f4ca45c1-9701-4ef0-a93d-78eb73b92509

📥 Commits

Reviewing files that changed from the base of the PR and between ae9ee8c and 627d9cc.

📒 Files selected for processing (10)

• README.md
• apps/server/src/mcp/McpHttpServer.test.ts
• apps/server/src/mcp/McpHttpServer.ts
• apps/server/src/mcp/toolkits/archive/handlers.test.ts
• apps/server/src/mcp/toolkits/archive/handlers.ts
• apps/server/src/mcp/toolkits/archive/tools.ts
• apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.test.ts
• apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.ts
• apps/server/src/orchestration/Services/ProjectionSnapshotQuery.ts
• docs/user/cli-automation.md

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