Add per-chat branch tracking and branch switch prompts

apps/web/src/components/ChatView.tsx

@@ -39,6 +39,7 @@ import { memo, useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { useNavigate, useSearch } from "@tanstack/react-router";
 import { useShallow } from "zustand/react/shallow";
 import { useGitStatus } from "~/lib/gitStatusState";
+import { resolveThreadBranchAutoLink } from "~/lib/threadBranchTracking";
 import { usePrimaryEnvironmentId } from "../environments/primary";
 import { readEnvironmentApi } from "../environmentApi";
 import { isElectron } from "../env";
@@ -150,6 +151,7 @@ import { resolveEffectiveEnvMode, resolveEnvironmentOptionLabel } from "./Branch
 import { ProviderStatusBanner } from "./chat/ProviderStatusBanner";
 import { ThreadErrorBanner } from "./chat/ThreadErrorBanner";
 import { ComposerBannerStack, type ComposerBannerStackItem } from "./chat/ComposerBannerStack";
+import { useThreadBranchTracking } from "./chat/useThreadBranchTracking";
 import {
   MAX_HIDDEN_MOUNTED_TERMINAL_THREADS,
   buildExpiredTerminalContextToastCopy,
@@ -1659,6 +1661,25 @@ export default function ChatView(props: ChatViewProps) {
       : (storeServerTerminalLaunchContext ?? null);
   // Default true while loading to avoid toolbar flicker.
   const isGitRepo = gitStatusQuery.data?.isRepo ?? true;
+  // Branch-tracking glue: auto-link the chat to its first observed branch
+  // and surface a mismatch banner with checkout/relink actions when the
+  // working tree drifts. Only meaningful for server threads inside a repo.
+  const { mismatchBannerItem: branchMismatchBannerItem } = useThreadBranchTracking({
+    threadRef: isServerThread ? activeThreadRef : null,
+    threadBranch: activeThread?.branch ?? null,
+    worktreePath: activeThread?.worktreePath ?? null,
+    projectCwd: activeProject?.cwd ?? null,
+    gitStatus: isGitRepo ? (gitStatusQuery.data ?? null) : null,
+    isSendInFlight: isSendBusy,
+  });
+  const composerBannerItemsWithBranchMismatch = useMemo<ComposerBannerStackItem[]>(() => {
+    if (!branchMismatchBannerItem) {
+      return composerBannerItems;
+    }
+    // Mismatch goes first: it actively blocks the user's mental model of
+    // "where will this run?" and we want it to be the front-of-stack item.
+    return [branchMismatchBannerItem, ...composerBannerItems];
+  }, [branchMismatchBannerItem, composerBannerItems]);
   const terminalShortcutLabelOptions = useMemo(
     () => ({
       context: {
@@ -2334,6 +2355,18 @@ export default function ChatView(props: ChatViewProps) {
     canOverrideServerThreadEnvMode && pendingServerThreadBranch !== undefined
       ? pendingServerThreadBranch
       : (activeThread?.branch ?? null);
+  const liveThreadBranch =
+    resolveThreadBranchAutoLink({
+      threadBranch: null,
+      gitStatus: gitStatusQuery.data ?? null,
+    })?.branch ?? null;
+  // First-send binding happens here, not when a new draft is opened. Drafts
+  // may carry a seeded branch from the previous chat or from the toolbar, but
+  // the actual chat link should reflect the working tree at send time.
+  const initialThreadBranch =
+    activeThread?.messages.length === 0
+      ? (liveThreadBranch ?? activeThreadBranch)
+      : (activeThreadBranch ?? liveThreadBranch);
   const sendEnvMode = resolveSendEnvMode({
     requestedEnvMode: envMode,
     isGitRepo,
@@ -2691,14 +2724,14 @@ export default function ChatView(props: ChatViewProps) {
     const isFirstMessage = !isServerThread || activeThread.messages.length === 0;
     const baseBranchForWorktree =
       isFirstMessage && sendEnvMode === "worktree" && !activeThread.worktreePath
-        ? activeThreadBranch
+        ? initialThreadBranch
         : null;
 
     // In worktree mode, require an explicit base branch so we don't silently
     // fall back to local execution when branch selection is missing.
     const shouldCreateWorktree =
       isFirstMessage && sendEnvMode === "worktree" && !activeThread.worktreePath;
-    if (shouldCreateWorktree && !activeThreadBranch) {
+    if (shouldCreateWorktree && !initialThreadBranch) {
       setThreadError(threadIdForSend, "Select a base branch before sending in New worktree mode.");
       return;
     }
@@ -2834,7 +2867,7 @@ export default function ChatView(props: ChatViewProps) {
                       modelSelection: threadCreateModelSelection,
                       runtimeMode,
                       interactionMode,
-                      branch: activeThreadBranch,
+                      branch: initialThreadBranch,
                       worktreePath: activeThread.worktreePath,
                       createdAt: activeThread.createdAt,
                     },
@@ -3288,7 +3321,7 @@ export default function ChatView(props: ChatViewProps) {
         modelSelection: nextThreadModelSelection,
         runtimeMode,
         interactionMode: "default",
-        branch: activeThreadBranch,
+        branch: initialThreadBranch,
         worktreePath: activeThread.worktreePath,
         createdAt,
       })
@@ -3351,7 +3384,7 @@ export default function ChatView(props: ChatViewProps) {
   }, [
     activeProject,
     activeProposedPlan,
-    activeThreadBranch,
+    initialThreadBranch,
     activeThread,
     beginLocalDispatch,
     activeEnvironmentUnavailable,
@@ -3602,7 +3635,10 @@ export default function ChatView(props: ChatViewProps) {
             )}
           >
             <div className="relative isolate">
-              <ComposerBannerStack className="relative z-0" items={composerBannerItems} />
+              <ComposerBannerStack
+                className="relative z-0"
+                items={composerBannerItemsWithBranchMismatch}
+              />
               <div className="relative z-10">
                 <ChatComposer
                   ref={composerRef}

apps/web/src/components/GitActionsControl.logic.test.ts

@@ -6,7 +6,6 @@ import {
   requiresDefaultBranchConfirmation,
   resolveAutoFeatureBranchName,
   resolveDefaultBranchActionDialogCopy,
-  resolveLiveThreadBranchUpdate,
   resolveQuickAction,
   resolveThreadBranchUpdate,
 } from "./GitActionsControl.logic";
@@ -1053,55 +1052,6 @@ describe("resolveThreadBranchUpdate", () => {
   });
 });
 
-describe("resolveLiveThreadBranchUpdate", () => {
-  it("returns a branch update when live git status differs from stored thread metadata", () => {
-    const update = resolveLiveThreadBranchUpdate({
-      threadBranch: "feature/old-ref",
-      gitStatus: status({ refName: "effect-atom" }),
-    });
-
-    assert.deepEqual(update, {
-      branch: "effect-atom",
-    });
-  });
-
-  it("returns null when live git status is unavailable", () => {
-    const update = resolveLiveThreadBranchUpdate({
-      threadBranch: "feature/old-ref",
-      gitStatus: null,
-    });
-
-    assert.equal(update, null);
-  });
-
-  it("returns null when the stored thread ref already matches git status", () => {
-    const update = resolveLiveThreadBranchUpdate({
-      threadBranch: "effect-atom",
-      gitStatus: status({ refName: "effect-atom" }),
-    });
-
-    assert.equal(update, null);
-  });
-
-  it("returns null when git status is detached HEAD but the thread already has a ref", () => {
-    const update = resolveLiveThreadBranchUpdate({
-      threadBranch: "effect-atom",
-      gitStatus: status({ refName: null }),
-    });
-
-    assert.equal(update, null);
-  });
-
-  it("does not regress a semantic thread ref back to a temporary worktree ref", () => {
-    const update = resolveLiveThreadBranchUpdate({
-      threadBranch: "t3code/github-query-rate-limit",
-      gitStatus: status({ refName: "t3code/bda76797" }),
-    });
-
-    assert.equal(update, null);
-  });
-});
-
 describe("resolveAutoFeatureBranchName", () => {
   it("uses semantic preferred ref names when available", () => {
     const ref = resolveAutoFeatureBranchName(["main", "feature/other"], "fix toast copy");

apps/web/src/components/GitActionsControl.logic.ts

@@ -3,7 +3,6 @@ import type {
   GitStackedAction,
   VcsStatusResult,
 } from "@t3tools/contracts";
-import { isTemporaryWorktreeBranch } from "@t3tools/shared/git";
 import {
   DEFAULT_CHANGE_REQUEST_TERMINOLOGY,
   getChangeRequestTerminology,
@@ -373,35 +372,11 @@ export function resolveThreadBranchUpdate(
   };
 }
 
-export function resolveLiveThreadBranchUpdate(input: {
-  threadBranch: string | null;
-  gitStatus: VcsStatusResult | null;
-}): { branch: string | null } | null {
-  if (!input.gitStatus) {
-    return null;
-  }
-
-  if (input.gitStatus.refName === null && input.threadBranch !== null) {
-    return null;
-  }
-
-  if (input.threadBranch === input.gitStatus.refName) {
-    return null;
-  }
-
-  if (
-    input.threadBranch !== null &&
-    input.gitStatus.refName !== null &&
-    !isTemporaryWorktreeBranch(input.threadBranch) &&
-    isTemporaryWorktreeBranch(input.gitStatus.refName)
-  ) {
-    return null;
-  }
-
-  return {
-    branch: input.gitStatus.refName,
-  };
-}
+// NOTE: `resolveLiveThreadBranchUpdate` was removed. It silently rewrote a
+// chat's `branch` whenever the working tree was on a different ref, which
+// conflicts with explicit per-chat branch tracking. The mismatch is now
+// surfaced to the user via the chat-view banner instead. See
+// `apps/web/src/lib/threadBranchTracking.ts`.
 
 // Re-export from shared for backwards compatibility in this module's exports
 export { resolveAutoFeatureBranchName } from "@t3tools/shared/git";

apps/web/src/components/GitActionsControl.tsx

@@ -39,7 +39,6 @@ import {
   type DefaultBranchConfirmableAction,
   requiresDefaultBranchConfirmation,
   resolveDefaultBranchActionDialogCopy,
-  resolveLiveThreadBranchUpdate,
   resolveQuickAction,
   resolveThreadBranchUpdate,
 } from "./GitActionsControl.logic";
@@ -1105,28 +1104,12 @@ export default function GitActionsControl({
     activeDraftThread?.envMode === "worktree" &&
     activeDraftThread.worktreePath === null;
 
-  useEffect(() => {
-    if (isGitActionRunning || isSelectingWorktreeBase) {
-      return;
-    }
-
-    const branchUpdate = resolveLiveThreadBranchUpdate({
-      threadBranch: activeServerThread?.branch ?? activeDraftThread?.branch ?? null,
-      gitStatus: gitStatusForActions,
-    });
-    if (!branchUpdate) {
-      return;
-    }
-
-    persistThreadBranchSync(branchUpdate.branch);
-  }, [
-    activeServerThread?.branch,
-    activeDraftThread?.branch,
-    gitStatusForActions,
-    isGitActionRunning,
-    isSelectingWorktreeBase,
-    persistThreadBranchSync,
-  ]);
+  // NOTE: We deliberately no longer auto-relink a chat's branch to whatever
+  // the working tree is currently on. Branch tracking now belongs to the chat
+  // (see lib/threadBranchTracking + chat/useThreadBranchTracking), and silent
+  // overwrites would defeat the mismatch banner's purpose. We still sync the
+  // branch *after explicit user actions* via syncThreadBranchAfterGitAction
+  // (e.g. when the user creates a feature branch through the menu).
 
   const isDefaultRef = useMemo(() => {
     return gitStatusForActions?.isDefaultRef ?? false;

apps/web/src/components/Sidebar.tsx

@@ -18,6 +18,7 @@ import {
   ThreadStatusLabel,
 } from "./ThreadStatusIndicators";
 import { ProjectFavicon } from "./ProjectFavicon";
+import { SidebarThreadBranchBadge } from "./SidebarThreadBranchBadge";
 import { autoAnimate } from "@formkit/auto-animate";
 import React, { useCallback, useEffect, memo, useMemo, useRef, useState } from "react";
 import { useShallow } from "zustand/react/shallow";
@@ -593,6 +594,7 @@ const SidebarThreadRow = memo(function SidebarThreadRow(props: SidebarThreadRowP
               </TooltipPopup>
             </Tooltip>
           )}
+          <SidebarThreadBranchBadge branch={thread.branch} />
         </div>
         <div className="ml-auto flex shrink-0 items-center gap-1.5">
           {terminalStatus && (

apps/web/src/components/SidebarThreadBranchBadge.tsx

@@ -0,0 +1,39 @@
+import { GitBranchIcon } from "lucide-react";
+import { memo } from "react";
+
+import { Tooltip, TooltipPopup, TooltipTrigger } from "./ui/tooltip";
+
+interface SidebarThreadBranchBadgeProps {
+  readonly branch: string | null;
+}
+
+/**
+ * Static branch label per chat row. Kept intentionally inert — no per-row
+ * git-status subscription — so we don't add N TanStack queries to the
+ * sidebar. Mismatch resolution happens in the chat header for the active
+ * thread, which is the only place the user can act on it anyway.
+ */
+export const SidebarThreadBranchBadge = memo(function SidebarThreadBranchBadge({
+  branch,
+}: SidebarThreadBranchBadgeProps) {
+  if (!branch) {
+    return null;
+  }
+  return (
+    <Tooltip>
+      <TooltipTrigger
+        render={
+          <span
+            aria-label={branch}
+            data-testid="sidebar-thread-branch-badge"
+            className="pointer-events-auto inline-flex h-4 max-w-[7rem] shrink-0 items-center gap-0.5 rounded-sm border border-border/50 bg-muted/40 px-1 font-mono text-[10px] leading-none tracking-tight text-muted-foreground/70"
+          >
+            <GitBranchIcon className="size-2.5 shrink-0" aria-hidden="true" />
+            <span className="truncate">{branch}</span>
+          </span>
+        }
+      />
+      <TooltipPopup side="top">{branch}</TooltipPopup>
+    </Tooltip>
+  );
+});