diff --git a/charts/workspace/server.py b/charts/workspace/server.py
index 7d31ecb..a096c62 100644
--- a/charts/workspace/server.py
+++ b/charts/workspace/server.py
@@ -861,6 +861,46 @@ def list_tasks(parent=None):
                 continue
         return tasks
 
+    @staticmethod
+    def reconcile_running(max_tasks=1000):
+        """Reconcile every non-terminal task once; return the count touched.
+
+        This is what the background TaskReconciler calls so a finished task's
+        completion hook fires (and finished_at / waiting-for-input update) even
+        when no client is reading it. Without it, _reconcile_status only runs
+        lazily on list/get/stream, so a headless webhook/cron callback can be
+        arbitrarily delayed — or never fire if nothing polls (issue #96).
+
+        Best-effort: a bad task dir is skipped, never raised. Terminal tasks
+        are skipped cheaply (no tmux subprocess).
+        """
+        ClaudeTaskManager.ensure_tasks_dir()
+        try:
+            entries = sorted(os.listdir(ClaudeTaskManager.TASKS_DIR), reverse=True)
+        except OSError:
+            return 0
+        reconciled = 0
+        for entry in entries[:max_tasks]:
+            task_dir = os.path.join(ClaudeTaskManager.TASKS_DIR, entry)
+            meta_path = os.path.join(task_dir, 'task.json')
+            if not os.path.isfile(meta_path):
+                continue
+            try:
+                with open(meta_path, 'r') as f:
+                    meta = json.load(f)
+            except (json.JSONDecodeError, OSError):
+                continue
+            # Cheap skip for terminal tasks — avoids the tmux has-session call.
+            if meta.get('status') not in ('running', 'waiting-for-input'):
+                continue
+            try:
+                ClaudeTaskManager._reconcile_status(meta, task_dir)
+                reconciled += 1
+            except Exception as e:
+                print(f'[task-reconciler] reconcile {entry} failed: {e}',
+                      file=sys.stderr)
+        return reconciled
+
     @staticmethod
     def get_task(task_id):
         task_dir = os.path.join(ClaudeTaskManager.TASKS_DIR, task_id)
@@ -6141,6 +6181,51 @@ def open_localhost(self):
         except Exception as e:
             self.send_error_response(f'Error opening localhost in Chrome: {str(e)}')
 
+class TaskReconciler:
+    """Single-process background poller that reconciles non-terminal task
+    status on an interval, so completion hooks fire and finished_at /
+    waiting-for-input update even when no client is reading the task.
+
+    Idempotent; safe to start once. Modeled on memory.sync.ClaudeMemorySyncer.
+    See issue #96.
+    """
+
+    _started = False
+    _thread = None
+    _stop_event = threading.Event()
+    _last_run_at = 0.0
+    _last_reconciled = 0
+    _start_lock = threading.Lock()
+
+    @classmethod
+    def start(cls, *, interval_seconds=10):
+        with cls._start_lock:
+            if cls._started:
+                return
+            cls._started = True
+
+        def _loop():
+            while not cls._stop_event.is_set():
+                try:
+                    cls._last_reconciled = ClaudeTaskManager.reconcile_running()
+                    cls._last_run_at = time.time()
+                except Exception as e:
+                    print(f'[task-reconciler] pass failed: {e}', file=sys.stderr)
+                cls._stop_event.wait(interval_seconds)
+
+        t = threading.Thread(target=_loop, name='task-reconciler', daemon=True)
+        cls._thread = t
+        t.start()
+
+    @classmethod
+    def status(cls):
+        return {
+            'running': cls._started and (cls._thread is not None and cls._thread.is_alive()),
+            'last_run_at': cls._last_run_at or None,
+            'last_reconciled': cls._last_reconciled,
+        }
+
+
 if __name__ == "__main__":
     # Change to the directory containing our files
     os.chdir('/tmp/browser')
@@ -6164,6 +6249,19 @@ def open_localhost(self):
         except Exception as e:
             print(f'[memory] syncer start failed: {e}', file=sys.stderr)
 
+    # Background task reconciler: flips finished tasks running -> completed and
+    # fires their completion hooks even when nothing is reading them, so headless
+    # webhook/cron callbacks are timely (issue #96).
+    try:
+        _reconcile_interval = int(os.environ.get('KC_RECONCILE_INTERVAL', '10'))
+    except (TypeError, ValueError):
+        _reconcile_interval = 10
+    try:
+        TaskReconciler.start(interval_seconds=_reconcile_interval)
+        print(f'[tasks] background reconciler started ({_reconcile_interval}s)')
+    except Exception as e:
+        print(f'[tasks] reconciler start failed: {e}', file=sys.stderr)
+
     print("Starting Browser API Server on port 6080...")
     print("Available endpoints:")
     print("  GET  /           - Browser interface")
diff --git a/charts/workspace/tests/task_reconciler_test.py b/charts/workspace/tests/task_reconciler_test.py
new file mode 100644
index 0000000..e7c121f
--- /dev/null
+++ b/charts/workspace/tests/task_reconciler_test.py
@@ -0,0 +1,152 @@
+"""Unit tests for the background task reconciler (issue #96).
+
+Covers ClaudeTaskManager.reconcile_running — the method the TaskReconciler
+daemon calls so a finished task's status flips and its completion hook fires
+even when no client is reading the task — plus the TaskReconciler lifecycle.
+
+tmux is simulated via subprocess.run stubs; TASKS_DIR is a tempdir;
+_fire_completion_hook is mocked so no network I/O happens.
+
+Run with:    python3 -m unittest tests.task_reconciler_test
+(from charts/workspace/)
+"""
+
+import json
+import os
+import shutil
+import sys
+import tempfile
+import unittest
+from unittest import mock
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+sys.path.insert(0, os.path.dirname(HERE))
+import server  # noqa: E402
+
+CTM = server.ClaudeTaskManager
+
+
+def _tmux_dead(*args, **kwargs):
+    """subprocess.run stub: tmux has-session reports the session is gone
+    (returncode 1); every other tmux op succeeds."""
+    argv = args[0] if args else kwargs.get('args', [])
+    if len(argv) >= 2 and argv[0] == 'tmux' and argv[1] == 'has-session':
+        return mock.Mock(returncode=1, stdout='', stderr='no session')
+    return mock.Mock(returncode=0, stdout='', stderr='')
+
+
+class ReconcileRunningTests(unittest.TestCase):
+    def setUp(self):
+        self.tmp = tempfile.mkdtemp(prefix='kcrecon-')
+        self._orig = CTM.TASKS_DIR
+        CTM.TASKS_DIR = self.tmp
+        self.addCleanup(self._restore)
+
+    def _restore(self):
+        CTM.TASKS_DIR = self._orig
+        shutil.rmtree(self.tmp, ignore_errors=True)
+
+    def _task(self, tid, **meta):
+        d = os.path.join(self.tmp, tid)
+        os.makedirs(d, exist_ok=True)
+        m = {'task_id': tid}
+        m.update(meta)
+        with open(os.path.join(d, 'task.json'), 'w') as f:
+            json.dump(m, f)
+        return d
+
+    def _read(self, tid):
+        with open(os.path.join(self.tmp, tid, 'task.json')) as f:
+            return json.load(f)
+
+    def test_dead_running_task_completes_and_fires_hook(self):
+        self._task('t1', status='running', tmux_session='kube-coder-t1',
+                   response_url='http://hook.example/cb')
+        with mock.patch.object(server.subprocess, 'run', side_effect=_tmux_dead), \
+             mock.patch.object(CTM, '_fire_completion_hook') as fire:
+            n = CTM.reconcile_running()
+        self.assertEqual(n, 1)
+        fire.assert_called_once()
+        meta = self._read('t1')
+        self.assertEqual(meta['status'], 'completed')
+        self.assertIn('finished_at', meta)
+        self.assertIn('hook_fired_at', meta)
+
+    def test_completes_without_hook_when_no_response_url(self):
+        self._task('t1', status='running', tmux_session='s')
+        with mock.patch.object(server.subprocess, 'run', side_effect=_tmux_dead), \
+             mock.patch.object(CTM, '_fire_completion_hook') as fire:
+            CTM.reconcile_running()
+        fire.assert_not_called()
+        self.assertEqual(self._read('t1')['status'], 'completed')
+
+    def test_terminal_tasks_skipped_without_tmux_call(self):
+        self._task('done', status='completed', tmux_session='x')
+        self._task('killed', status='killed', tmux_session='y')
+        with mock.patch.object(server.subprocess, 'run') as run:
+            n = CTM.reconcile_running()
+        self.assertEqual(n, 0)
+        run.assert_not_called()  # terminal → cheap skip, no subprocess
+
+    def test_live_session_stays_running(self):
+        self._task('t1', status='running', tmux_session='kube-coder-t1')
+        # has-session returns 0 (alive); capture-pane returns stable output.
+        with mock.patch.object(server.subprocess, 'run',
+                               return_value=mock.Mock(returncode=0, stdout='x', stderr='')), \
+             mock.patch.object(CTM, '_fire_completion_hook') as fire:
+            n = CTM.reconcile_running()
+        self.assertEqual(n, 1)
+        fire.assert_not_called()
+        self.assertEqual(self._read('t1')['status'], 'running')
+
+    def test_corrupt_and_missing_meta_skipped(self):
+        # A corrupt task dir + a dir with no task.json must not break the pass.
+        bad = os.path.join(self.tmp, 'bad'); os.makedirs(bad)
+        with open(os.path.join(bad, 'task.json'), 'w') as f:
+            f.write('{not json')
+        os.makedirs(os.path.join(self.tmp, 'nometa'))
+        self._task('good', status='running', tmux_session='s')
+        with mock.patch.object(server.subprocess, 'run', side_effect=_tmux_dead), \
+             mock.patch.object(CTM, '_fire_completion_hook'):
+            n = CTM.reconcile_running()
+        self.assertEqual(n, 1)  # only the good running task
+
+    def test_missing_tasks_dir_returns_zero(self):
+        CTM.TASKS_DIR = os.path.join(self.tmp, 'gone')
+        shutil.rmtree(self.tmp, ignore_errors=True)
+        # ensure_tasks_dir recreates it empty → zero tasks, no raise.
+        self.assertEqual(CTM.reconcile_running(), 0)
+
+    def test_max_tasks_bound(self):
+        for i in range(5):
+            self._task(f't{i}', status='running', tmux_session='s')
+        with mock.patch.object(server.subprocess, 'run', side_effect=_tmux_dead), \
+             mock.patch.object(CTM, '_fire_completion_hook'):
+            n = CTM.reconcile_running(max_tasks=2)
+        self.assertEqual(n, 2)
+
+    def test_reconcile_failure_does_not_raise(self):
+        self._task('t1', status='running', tmux_session='s')
+        with mock.patch.object(CTM, '_reconcile_status', side_effect=RuntimeError('boom')):
+            n = CTM.reconcile_running()  # must swallow + continue
+        self.assertEqual(n, 0)
+
+
+class TaskReconcilerLifecycleTests(unittest.TestCase):
+    def test_start_is_idempotent(self):
+        orig = server.TaskReconciler._started
+        server.TaskReconciler._started = True
+        try:
+            # Second start() must be a no-op and must not raise / spawn a thread.
+            server.TaskReconciler.start(interval_seconds=10)
+        finally:
+            server.TaskReconciler._started = orig
+
+    def test_status_shape(self):
+        s = server.TaskReconciler.status()
+        for k in ('running', 'last_run_at', 'last_reconciled'):
+            self.assertIn(k, s)
+
+
+if __name__ == '__main__':
+    unittest.main()