diff --git a/src/resources/extensions/gsd/index.ts b/src/resources/extensions/gsd/index.ts
index b92317a7f..b20d4ee42 100644
--- a/src/resources/extensions/gsd/index.ts
+++ b/src/resources/extensions/gsd/index.ts
@@ -795,6 +795,12 @@ export default function (pi: ExtensionAPI) {
 
   // ── agent_end: auto-mode advancement or auto-start after discuss ───────────
   pi.on("agent_end", async (event, ctx: ExtensionContext) => {
+    // Clean up quick-task branch if one just completed (#1269)
+    try {
+      const { cleanupQuickBranch } = await import("./quick.js");
+      cleanupQuickBranch();
+    } catch { /* non-fatal */ }
+
     // If discuss phase just finished, start auto-mode
     if (checkAutoStartAfterDiscuss()) {
       depthVerifiedMilestones.clear();
diff --git a/src/resources/extensions/gsd/quick.ts b/src/resources/extensions/gsd/quick.ts
index 299b48a2a..41269abba 100644
--- a/src/resources/extensions/gsd/quick.ts
+++ b/src/resources/extensions/gsd/quick.ts
@@ -107,10 +107,11 @@ export async function handleQuick(
   const skipBranch = git.prefs.isolation === "none";
 
   let branchCreated = false;
+  let originalBranch: string | undefined;
   if (!skipBranch) {
     try {
-      const current = git.getCurrentBranch();
-      if (current !== branchName) {
+      originalBranch = git.getCurrentBranch();
+      if (originalBranch !== branchName) {
         // Auto-commit any dirty state before switching
         try {
           git.autoCommit("quick-task", `Q${taskNum}`, []);
@@ -154,4 +155,57 @@ export async function handleQuick(
     },
     { triggerTurn: true },
   );
+
+  // Schedule branch merge-back after the quick task agent session ends.
+  // Without this, auto-mode resumes on the quick-task branch (#1269).
+  if (branchCreated && originalBranch) {
+    _pendingQuickBranchReturn = {
+      basePath,
+      originalBranch,
+      quickBranch: branchName,
+      taskNum,
+      slug,
+      description,
+    };
+  }
+}
+
+/** Pending quick-task branch return — consumed by cleanupQuickBranch(). */
+let _pendingQuickBranchReturn: {
+  basePath: string;
+  originalBranch: string;
+  quickBranch: string;
+  taskNum: number;
+  slug: string;
+  description: string;
+} | null = null;
+
+/**
+ * Merge the quick-task branch back to the original branch and switch.
+ * Called from the agent_end handler after a quick task completes.
+ * Returns true if a branch return was performed.
+ */
+export function cleanupQuickBranch(): boolean {
+  if (!_pendingQuickBranchReturn) return false;
+  const { basePath, originalBranch, quickBranch, taskNum, slug, description } = _pendingQuickBranchReturn;
+  _pendingQuickBranchReturn = null;
+
+  try {
+    // Auto-commit any remaining work
+    try { runGit(basePath, ["add", "-A"]); } catch {}
+    try { runGit(basePath, ["commit", "-m", `quick(Q${taskNum}): ${slug}`]); } catch {}
+
+    // Switch back and merge
+    runGit(basePath, ["checkout", originalBranch]);
+    try {
+      runGit(basePath, ["merge", "--squash", quickBranch]);
+      runGit(basePath, ["commit", "-m", `quick(Q${taskNum}): ${description.slice(0, 72)}`]);
+    } catch { /* merge conflict or nothing — non-fatal */ }
+
+    // Clean up quick branch
+    try { runGit(basePath, ["branch", "-D", quickBranch]); } catch {}
+    return true;
+  } catch {
+    return false;
+  }
 }