fix: gstack-brain-sync advances the artifacts worktree after push

bin/gstack-brain-sync

@@ -43,6 +43,21 @@ remote_auth_hint() {
   esac
 }
 
+# Advance the artifacts worktree (the path gbrain indexes) to the parent
+# repo's current HEAD. Best-effort: failures are non-fatal because the push
+# has already succeeded, so the local index can catch up on the next run.
+# Without this, the worktree stays at its init commit and gbrain reports
+# 0 pages while artifacts pile up in main.
+advance_brain_worktree_to_head() {
+  local worktree="${GSTACK_BRAIN_WORKTREE:-$HOME/.gstack-brain-worktree}"
+  if [ ! -d "$worktree/.git" ] && [ ! -f "$worktree/.git" ]; then
+    return 0
+  fi
+  local sha
+  sha=$(git -C "$GSTACK_HOME" rev-parse HEAD 2>/dev/null) || return 0
+  ( cd "$worktree" && git checkout --detach "$sha" >/dev/null 2>&1 ) || true
+}
+
 write_status() {
   # args: status_code message [extra_json_blob]
   local code="$1"
@@ -306,6 +321,7 @@ subcmd_once() {
           : > "$QUEUE"
           date -u +%Y-%m-%dT%H:%M:%SZ > "$LAST_PUSH_FILE"
           write_status "ok" "pushed $n file(s) after rebase"
+          advance_brain_worktree_to_head
           exit 0
         fi
       fi
@@ -319,6 +335,7 @@ subcmd_once() {
   : > "$QUEUE"
   date -u +%Y-%m-%dT%H:%M:%SZ > "$LAST_PUSH_FILE"
   write_status "ok" "pushed $n file(s)"
+  advance_brain_worktree_to_head
   exit 0
 }
 

test/brain-sync.test.ts

@@ -255,6 +255,51 @@ describe('init + sync + restore round-trip', () => {
     expect(log.stdout).toMatch(/sync: 1 file/);
   });
 
+  test('--once advances the brain worktree HEAD to match parent after push', () => {
+    // The brain worktree is what gbrain indexes from. If --once commits +
+    // pushes but leaves the detached worktree behind, gbrain reports
+    // 0 pages and recent artifacts never become searchable.
+    run(['gstack-artifacts-init', '--remote', bareRemote]);
+    run(['gstack-config', 'set', 'artifacts_sync_mode', 'full']);
+
+    // Set up a detached worktree at the init commit, mirroring what
+    // gstack-gbrain-source-wireup does in real installs.
+    const worktree = fs.mkdtempSync(path.join(os.tmpdir(), 'brain-worktree-'));
+    fs.rmSync(worktree, { recursive: true, force: true });
+    const initSha = git(['rev-parse', 'HEAD'], tmpHome).stdout.trim();
+    const addRes = spawnSync(
+      'git',
+      ['-C', tmpHome, 'worktree', 'add', '--detach', worktree, initSha],
+      { encoding: 'utf-8' },
+    );
+    expect(addRes.status).toBe(0);
+
+    // Enqueue + sync. brain-sync should commit, push, AND advance the
+    // worktree's detached HEAD to the new commit.
+    fs.mkdirSync(path.join(tmpHome, 'projects', 'p'), { recursive: true });
+    fs.writeFileSync(
+      path.join(tmpHome, 'projects/p/learnings.jsonl'),
+      '{"skill":"x","insight":"y","ts":"2026-04-22T10:00:00Z"}\n',
+    );
+    run(['gstack-brain-enqueue', 'projects/p/learnings.jsonl']);
+    const r = run(['gstack-brain-sync', '--once'], {
+      env: { GSTACK_BRAIN_WORKTREE: worktree },
+    });
+    expect(r.status).toBe(0);
+
+    const parentSha = git(['rev-parse', 'HEAD'], tmpHome).stdout.trim();
+    const worktreeSha = git(['rev-parse', 'HEAD'], worktree).stdout.trim();
+    expect(parentSha).not.toBe(initSha); // sanity: commit actually happened
+    expect(worktreeSha).toBe(parentSha); // the actual regression check
+    expect(
+      fs.existsSync(path.join(worktree, 'projects/p/learnings.jsonl')),
+    ).toBe(true);
+
+    // Cleanup.
+    spawnSync('git', ['-C', tmpHome, 'worktree', 'remove', '--force', worktree]);
+    fs.rmSync(worktree, { recursive: true, force: true });
+  });
+
   test('restore round-trip: writes on machine A visible on machine B', () => {
     // Machine A.
     run(['gstack-artifacts-init', '--remote', bareRemote]);