fix(server): settle cancelled worktree setup before rollback

[juliusmarminge]

Cancelling a worktree bootstrap interrupted its failure handler before it could publish the cancelled outcome or roll back the thread. Clients could keep showing setup as running after the task stopped.

Keep the bootstrap interruptible while letting its settlement handler finish recording the outcome, closing the setup terminal, removing the worktree, and rolling back the thread. A focused router test verifies the cancelled receipt, deleted thread, failed original dispatch, and absence of an agent turn; the existing synchronous and asynchronous handoff cases still pass.

Validation: all three focused setup router cases pass, server typecheck passes, and targeted lint has no errors. This changes server settlement only; screenshots are not applicable.

Implemented with GPT-6 in Codex.

Summary by CodeRabbit

• Bug Fixes
  • Improved cancellation handling during synchronous worktree setup.
  • Cancelled setup now reports a clear “Worktree setup cancelled.” error and cleans up the temporary bootstrap thread.
  • Prevented the bootstrap turn from starting after setup is cancelled.
  • Ensured cancellation cleanup and rollback complete reliably before the operation ends.

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.6 KiB	13.6 KiB	+18 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	+2 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.6 KiB	6.6 KiB	+16 B (+0.2%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	57.1 KiB	57.1 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.6 KiB	−4 B (−0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+1 B (+0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.5 KiB	6.5 KiB	−5 B (−0.1%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.8 KiB	57.8 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: 962bf62 · PR result: 51c0812 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 113.9 KiB
• Claude decoded thread snapshot: 114.6 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[macroscopeapp]

Approvability

Verdict: Approved at 51c0812

Macroscope's review found this PR approvable — This narrowly fixes cancelled worktree setup by allowing cancellation to reach the existing rollback path and ensuring the cancellation outcome and cleanup finish atomically. A focused server test verifies the thread is deleted, the cancelled activity is recorded, and no turn starts.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Team

Run ID: c08b7252-22ed-40fc-ba7f-59407d2b8671

📥 Commits

Reviewing files that changed from the base of the PR and between 962bf62 and 51c0812.

📒 Files selected for processing (2)

• apps/server/src/server.test.ts
• apps/server/src/ws.ts

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📝 Walkthrough

Walkthrough

Worktree setup cancellation now interrupts the bootstrap program, protects cleanup and rollback, deletes the bootstrap thread, reports cancellation, and prevents turn dispatch. Tests cover the cancellation result and related dispatch metadata.

Changes

Worktree setup cancellation

Layer / File(s)	Summary
Cancellation flow and validation apps/server/src/ws.ts, apps/server/src/server.test.ts	The bootstrap program is interruptible during setup and uninterruptible during cancellation cleanup and rollback. Tests verify the cancelled outcome, deleted bootstrap thread, failed dispatch metadata, and absent turn dispatch.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant CancellationRPC
  participant BootstrapProgram
  participant TurnDispatch
  CancellationRPC->>BootstrapProgram: interrupt running setup
  BootstrapProgram->>BootstrapProgram: complete cleanup and rollback
  BootstrapProgram->>CancellationRPC: report cancellation and deleted thread
  BootstrapProgram-->>TurnDispatch: fail dispatch without starting a turn

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Suggested reviewers: t3dotgg

Merge Risk: ⚪ Minimal · up to 51c08

Cancelled worktree setup completes its cleanup and reports the cancelled result without starting an agent turn. No current merge-blocking risk was identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
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.
Title check	✅ Passed	The title clearly and concisely describes the main change: settling cancelled worktree setup before rollback.
Description check	✅ Passed	The description explains what changed, why it was needed, the test coverage, and that UI changes do not apply. It does not use the template headings or checklist, but it contains the required informat…

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch mobile-worktree-setup/cancellation

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