diff --git a/custom_components/localthings/observe.py b/custom_components/localthings/observe.py
index e82800f..94f1d20 100644
--- a/custom_components/localthings/observe.py
+++ b/custom_components/localthings/observe.py
@@ -87,6 +87,7 @@ class ObserveManager:
         """Blocking — subscribes to every href then sleeps for the whole
         grace period. Caller must run this in an executor, never on the
         event loop."""
+        self._notified.clear()
         subscribed: set[str] = set()
         for href in hrefs:
             segs = [s for s in href.strip('/').split('/') if s]
diff --git a/tests/localthings/test_observe.py b/tests/localthings/test_observe.py
index f9cafb2..c6fc68f 100644
--- a/tests/localthings/test_observe.py
+++ b/tests/localthings/test_observe.py
@@ -1,6 +1,7 @@
 """Tests for ObserveManager: write-settle guard and mode defaults."""
 from __future__ import annotations
 
+import threading
 import time
 
 import cbor2
@@ -78,15 +79,18 @@ def test_try_enter_observe_mode_succeeds_when_all_hrefs_notify():
     session = _FakeSession()
     hrefs = ['/oven/vs/0', '/power/vs/0']
 
-    def _notify_all():
+    def _notify_during_grace_period():
+        # Simulate notifications arriving during the grace period
+        time.sleep(0.005)  # Let the sleep start, then notify partway through
         for href in hrefs:
             mgr.on_notification(href, cbor2.dumps({'x': 1}))
 
-    # Grace period is real time.sleep() in the manager; keep it tiny and
-    # notify synchronously beforehand so notifies are already recorded
-    # when the (short) sleep completes.
-    _notify_all()
-    entered = mgr.try_enter_observe_mode(session, hrefs, grace_period_s=0.01)
+    # Start background thread to deliver notifications during grace period
+    notifier = threading.Thread(target=_notify_during_grace_period, daemon=True)
+    notifier.start()
+
+    entered = mgr.try_enter_observe_mode(session, hrefs, grace_period_s=0.02)
+    notifier.join()
 
     assert entered is True
     assert mgr.mode == 'observe'
@@ -121,12 +125,20 @@ def test_try_enter_observe_mode_meets_success_fraction_with_partial_notifies():
     mgr = _manager()
     session = _FakeSession()
     hrefs = ['/a/vs/0', '/b/vs/0', '/c/vs/0', '/d/vs/0']
-    for href in hrefs[:3]:  # 3/4 = 0.75, below default 0.8 threshold
-        mgr.on_notification(href, cbor2.dumps({'x': 1}))
+
+    def _notify_partial():
+        # Simulate partial notifications arriving during grace period
+        time.sleep(0.005)
+        for href in hrefs[:3]:  # 3/4 = 0.75
+            mgr.on_notification(href, cbor2.dumps({'x': 1}))
+
+    notifier = threading.Thread(target=_notify_partial, daemon=True)
+    notifier.start()
 
     entered = mgr.try_enter_observe_mode(
-        session, hrefs, grace_period_s=0.01, success_fraction=0.7,
+        session, hrefs, grace_period_s=0.02, success_fraction=0.7,
     )
+    notifier.join()
 
     assert entered is True
     assert mgr.mode == 'observe'
@@ -136,3 +148,44 @@ def test_on_notification_ignores_malformed_cbor():
     mgr = _manager()
     mgr.on_notification('/oven/vs/0', b'\xff\xff\xff not cbor')
     assert mgr.cache.get('/oven/vs/0') is None
+
+
+def test_try_enter_observe_mode_clears_stale_notifications_on_retry():
+    """Regression test: verify second call to try_enter_observe_mode() doesn't
+    get polluted by notifications from the first call. This happens in real
+    usage when poll-only mode periodically retries entering observe mode."""
+    mgr = _manager()
+    session = _FakeSession()
+    hrefs = ['/a/vs/0', '/b/vs/0']
+
+    # First call: all hrefs notify -> succeeds and enters observe mode
+    def _notify_all_first():
+        time.sleep(0.005)
+        for href in hrefs:
+            mgr.on_notification(href, cbor2.dumps({'x': 1}))
+
+    notifier1 = threading.Thread(target=_notify_all_first, daemon=True)
+    notifier1.start()
+    entered = mgr.try_enter_observe_mode(session, hrefs, grace_period_s=0.02)
+    notifier1.join()
+    assert entered is True
+    assert mgr.mode == 'observe'
+
+    # Second call: retry with same hrefs, but only one notifies.
+    # Without the fix (missing self._notified.clear()), the old notifications
+    # would leak in, making this appear successful (2/2 instead of 1/2).
+    # With the fix, it should fail because only 1/2 < 0.8.
+    session.subscribed = []  # reset for clean test
+
+    def _notify_partial_second():
+        time.sleep(0.005)
+        mgr.on_notification(hrefs[0], cbor2.dumps({'x': 2}))  # only one notifies
+
+    notifier2 = threading.Thread(target=_notify_partial_second, daemon=True)
+    notifier2.start()
+    entered = mgr.try_enter_observe_mode(session, hrefs, grace_period_s=0.02)
+    notifier2.join()
+
+    assert entered is False
+    assert mgr.mode == 'poll'
+    assert mgr.subscribed_hrefs == set()