Allow empty server threads to bootstrap new worktrees

[juliusmarminge]

Summary

• Enables empty server threads to enter New worktree mode and bootstrap the first send without forcing a separate draft thread.
• Preserves selected base-branch state for empty server threads so branch changes made in the toolbar are used when creating the worktree.
• Clarifies workspace labeling for locked env mode states and adds logic coverage for the new send/env-mode behavior.
• Adds browser-level coverage for first-send worktree bootstrap and base-branch selection on empty server threads.

Testing

• bun fmt
• bun lint
• bun typecheck
• bun run test
• Browser flow checks added in apps/web/src/components/ChatView.browser.tsx for:
  • bootstrapping the first send in New worktree mode from an empty server thread
  • updating the selected worktree base branch before send

---

Note

Medium Risk
Medium risk because it changes first-send behavior and branch/env-mode selection for server threads, which affects worktree creation and command dispatch paths; mistakes could create worktrees off the wrong base branch or leave UI state inconsistent.

Overview
Enables empty server threads (no messages, no worktree) to temporarily opt into New worktree mode, select a base branch in the toolbar, and have that choice used to bootstrap worktree creation on the first send (via pending overrides cleared on thread switch / when no longer eligible).

Extracts temporary-worktree branch utilities into @t3tools/shared/git (WORKTREE_BRANCH_PREFIX, buildTemporaryWorktreeBranchName, isTemporaryWorktreeBranch) and updates server/web to use them, while adding resolveSendEnvMode to force local sends for non-git repos.

UI/UX tweaks: introduces resolveLockedWorkspaceLabel so locked workspace state shows shorter labels, and expands unit + browser tests to cover the new first-send bootstrap and override-reset flows.

^{Reviewed by Cursor Bugbot for commit ae19339. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Allow empty server threads to bootstrap new worktrees with a user-selected base branch

• Adds pendingServerThreadEnvMode and pendingServerThreadBranch state to ChatView.tsx so empty server threads can remain in 'New worktree' mode before the first message is sent.
• On first send, calls prepareWorktree using a temporary t3code/<8-hex> branch name generated by the new buildTemporaryWorktreeBranchName helper in packages/shared/src/git.ts.
• Centralizes WORKTREE_BRANCH_PREFIX, buildTemporaryWorktreeBranchName, and isTemporaryWorktreeBranch into the shared git module, removing duplicate definitions from ChatView.logic.ts and ProviderCommandReactor.ts.
• Adds resolveSendEnvMode in ChatView.logic.ts to force non-git repositories to 'local' mode regardless of the user's selected env mode.
• Updates BranchToolbar and BranchToolbarBranchSelector to accept override props for env mode and active branch, enabling the pre-send selection UI for empty server threads.

^{Macroscope summarized ae19339.}

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Pending override state leaks between empty server threads
  • Added a ref to track the previous thread ID so the cleanup effect resets pendingServerThreadEnvMode and pendingServerThreadBranch whenever activeThread.id changes, even when canOverrideServerThreadEnvMode remains true for both threads.

Or push these changes by commenting:

@cursor push a440ab779e

Preview (a440ab779e)

diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -2228,12 +2228,15 @@
     isGitRepo,
   });
 
+  const prevThreadIdForPendingReset = useRef(activeThread?.id);
   useEffect(() => {
-    if (canOverrideServerThreadEnvMode) {
-      return;
+    const threadChanged = prevThreadIdForPendingReset.current !== activeThread?.id;
+    prevThreadIdForPendingReset.current = activeThread?.id;
+
+    if (threadChanged || !canOverrideServerThreadEnvMode) {
+      setPendingServerThreadEnvMode(null);
+      setPendingServerThreadBranch(undefined);
     }
-    setPendingServerThreadEnvMode(null);
-    setPendingServerThreadBranch(undefined);
   }, [canOverrideServerThreadEnvMode, activeThread?.id]);
 
   useEffect(() => {

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces new feature capability allowing empty server threads to be configured for worktree mode before the first message is sent. While well-tested and the code is reasonable, this changes runtime behavior for thread bootstrapping workflows and introduces new user-facing functionality that warrants human review.

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