Fix new-thread draft reuse for worktree defaults

[juliusmarminge]

Summary

• Prevents the new-thread flow from reusing an existing draft when the project default environment mode is worktree.
• Preserves promoting draft threads so they are not reused while promotion is still in progress.
• Adds coverage for the sidebar seed-context logic and the browser-level new-thread flow.

Testing

• bun fmt
• bun lint
• bun typecheck
• bun run test
• Not run: additional manual verification beyond the automated tests

---

Note

Medium Risk
Touches new-thread draft creation/reuse logic and draft-store cleanup rules, which can impact routing and draft persistence across projects. Changes are localized and covered by new unit and browser-level tests, reducing regression risk.

Overview
New-thread draft reuse is tightened for worktree defaults and promotion in-flight. When the project default env mode is worktree, sidebar seed context now forces envMode: "worktree" instead of inheriting an active thread’s branch/worktree path, ensuring the next thread starts as a fresh worktree draft.

Draft reuse/cleanup is also guarded so promoting draft threads aren’t reused or deleted mid-promotion (useHandleNewThread checks promotedTo == null; composerDraftStore won’t evict a prior draft if it’s promoting). Adds regression coverage in ChatView.browser.tsx and Sidebar.logic.test.ts.

^{Reviewed by Cursor Bugbot for commit 33d6b03. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix new-thread draft reuse when the default environment mode is worktree

• Fixes two bugs in the new-thread flow: promoting drafts were being reused instead of creating a new draft, and worktree-defaulted projects were inheriting branch/path context from active threads.
• In useHandleNewThread.ts, draft reuse is now skipped when the active draft has already been promoted (promotedTo != null).
• In composerDraftStore.ts, deletion of a previous logical-project draft is skipped when that draft is in a promoting state.
• In Sidebar.logic.ts, resolveSidebarNewThreadSeedContext returns { envMode: 'worktree' } immediately when defaultEnvMode is 'worktree', ignoring any active thread context.

^{Macroscope summarized 33d6b03.}

[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: fc5eb936-4c33-4383-bf48-15c5c0aaa69d

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
• Commit unit tests in branch t3code/investigate-issue-1989

---

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

[macroscopeapp]

Approvability

Verdict: Approved

Small bug fix adding guard conditions to prevent incorrect draft thread reuse when worktree defaults are set or when drafts are being promoted. Production changes are minimal (~12 lines) with defensive null/state checks, accompanied by comprehensive test coverage (~114 lines). Low-risk, well-scoped fix.

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