From afdfe16931d292ed5de2772ccc1afd95120ff6b2 Mon Sep 17 00:00:00 2001
From: Julius Marminge <julius0216@outlook.com>
Date: Tue, 17 Feb 2026 13:05:30 -0800
Subject: [PATCH] Extract branch sync logic and limit sync to local mode

- move branch-sync decision into `BranchToolbar.logic.ts`
- avoid auto-sync when env mode is `worktree` or thread has worktree path
- add unit tests for sync and no-sync cases
---
 .../components/BranchToolbar.logic.test.ts    | 56 +++++++++++++++++++
 .../web/src/components/BranchToolbar.logic.ts | 28 ++++++++++
 apps/web/src/components/BranchToolbar.tsx     | 18 ++++--
 3 files changed, 96 insertions(+), 6 deletions(-)
 create mode 100644 apps/web/src/components/BranchToolbar.logic.test.ts
 create mode 100644 apps/web/src/components/BranchToolbar.logic.ts

diff --git a/apps/web/src/components/BranchToolbar.logic.test.ts b/apps/web/src/components/BranchToolbar.logic.test.ts
new file mode 100644
index 0000000000000000000000000000000000000000..dd2a25d06999f166a6d838a349376b000b2c5246
--- /dev/null
+++ b/apps/web/src/components/BranchToolbar.logic.test.ts
@@ -0,0 +1,56 @@
+import type { GitBranch } from "@t3tools/contracts";
+import { describe, expect, it } from "vitest";
+import { deriveSyncedLocalBranch } from "./BranchToolbar.logic";
+
+const branches: GitBranch[] = [
+  {
+    name: "main",
+    current: true,
+    isDefault: true,
+    worktreePath: null,
+  },
+  {
+    name: "feature/demo",
+    current: false,
+    isDefault: false,
+    worktreePath: null,
+  },
+];
+
+describe("deriveSyncedLocalBranch", () => {
+  it("syncs to git current branch in local mode", () => {
+    const result = deriveSyncedLocalBranch({
+      activeThreadId: "thread-1",
+      activeWorktreePath: null,
+      envMode: "local",
+      activeThreadBranch: "feature/demo",
+      queryBranches: branches,
+    });
+
+    expect(result).toBe("main");
+  });
+
+  it("does not sync when creating a new worktree", () => {
+    const result = deriveSyncedLocalBranch({
+      activeThreadId: "thread-1",
+      activeWorktreePath: null,
+      envMode: "worktree",
+      activeThreadBranch: "feature/demo",
+      queryBranches: branches,
+    });
+
+    expect(result).toBeNull();
+  });
+
+  it("does not sync when thread already targets a worktree path", () => {
+    const result = deriveSyncedLocalBranch({
+      activeThreadId: "thread-1",
+      activeWorktreePath: "/tmp/repo/worktrees/feature-demo",
+      envMode: "local",
+      activeThreadBranch: "feature/demo",
+      queryBranches: branches,
+    });
+
+    expect(result).toBeNull();
+  });
+});
diff --git a/apps/web/src/components/BranchToolbar.logic.ts b/apps/web/src/components/BranchToolbar.logic.ts
new file mode 100644
index 0000000000000000000000000000000000000000..03d04bc3cf39c65a66edd6480242c201abc9ca19
--- /dev/null
+++ b/apps/web/src/components/BranchToolbar.logic.ts
@@ -0,0 +1,28 @@
+import type { GitBranch } from "@t3tools/contracts";
+
+interface DeriveSyncedLocalBranchInput {
+  activeThreadId: string | undefined;
+  activeWorktreePath: string | null;
+  envMode: "local" | "worktree";
+  activeThreadBranch: string | null;
+  queryBranches: GitBranch[] | undefined;
+}
+
+export function deriveSyncedLocalBranch({
+  activeThreadId,
+  activeWorktreePath,
+  envMode,
+  activeThreadBranch,
+  queryBranches,
+}: DeriveSyncedLocalBranchInput): string | null {
+  if (!activeThreadId || activeWorktreePath || envMode !== "local") {
+    return null;
+  }
+
+  const currentBranch = queryBranches?.find((branch) => branch.current);
+  if (!currentBranch || currentBranch.name === activeThreadBranch) {
+    return null;
+  }
+
+  return currentBranch.name;
+}
diff --git a/apps/web/src/components/BranchToolbar.tsx b/apps/web/src/components/BranchToolbar.tsx
index 1e6dd9e923c3f22153196bd54f5fabc61a5d1e33..30e9327060664b1012d1b59b8a910e34042b6c43 100644
--- a/apps/web/src/components/BranchToolbar.tsx
+++ b/apps/web/src/components/BranchToolbar.tsx
@@ -9,6 +9,7 @@ import {
   gitCreateBranchAndCheckoutMutationOptions,
 } from "../lib/gitReactQuery";
 import { useStore } from "../store";
+import { deriveSyncedLocalBranch } from "./BranchToolbar.logic";
 import { Button } from "./ui/button";
 import {
   Combobox,
@@ -86,17 +87,22 @@ export default function BranchToolbar({
   // Keep thread branch synced to git current branch for local threads.
   const queryBranches = branchesQuery.data?.branches;
   useEffect(() => {
-    if (!activeThreadId || activeWorktreePath) return;
-    const current = queryBranches?.find((branch) => branch.current);
-    if (!current) return;
-    if (current.name === activeThreadBranch) return;
+    const syncedBranch = deriveSyncedLocalBranch({
+      activeThreadId,
+      activeWorktreePath,
+      envMode,
+      activeThreadBranch,
+      queryBranches,
+    });
+    if (!syncedBranch) return;
+
     dispatch({
       type: "SET_THREAD_BRANCH",
       threadId: activeThreadId,
-      branch: current.name,
+      branch: syncedBranch,
       worktreePath: null,
     });
-  }, [activeThreadId, activeWorktreePath, activeThreadBranch, queryBranches, dispatch]);
+  }, [activeThreadId, activeWorktreePath, activeThreadBranch, queryBranches, envMode, dispatch]);
 
   useEffect(() => {
     if (isBranchMenuOpen) return;
-- 
2.54.0