diff --git a/backend/api/routers/dub_core.py b/backend/api/routers/dub_core.py
index 448a6044..87c483f8 100644
--- a/backend/api/routers/dub_core.py
+++ b/backend/api/routers/dub_core.py
@@ -886,6 +886,7 @@ class _ASRWorkLifetime:
         import threading
         self._lock = threading.Lock()
         self._closed = threading.Event()
+        self._cleaned = False
 
     def run(self, fn):
         with self._lock:
@@ -900,6 +901,10 @@ class _ASRWorkLifetime:
     def cleanup(self, fn):
         self.stop()
         with self._lock:
+            if self._cleaned:
+                return
+            # Claim cleanup before invoking even a non-idempotent unload.
+            self._cleaned = True
             return fn()
 
 
diff --git a/tests/test_dub_transcribe.py b/tests/test_dub_transcribe.py
index e6a1175a..02092ad9 100644
--- a/tests/test_dub_transcribe.py
+++ b/tests/test_dub_transcribe.py
@@ -974,6 +974,7 @@ def test_stream_cleanup_waits_for_native_work_and_rejects_late_work():
     from api.routers.dub_core import _ASRWorkLifetime
     lifetime = _ASRWorkLifetime()
     started, release, cleaned = threading.Event(), threading.Event(), threading.Event()
+    cleanup_started = threading.Event()
     events = []
     def native():
         started.set()
@@ -986,9 +987,13 @@ def test_stream_cleanup_waits_for_native_work_and_rejects_late_work():
         work = pool.submit(lifetime.run, native)
         assert started.wait(5)
         lifetime.stop()
-        removal = pool.submit(lifetime.cleanup, cleanup)
+        def remove():
+            cleanup_started.set()
+            lifetime.cleanup(cleanup)
+        removal = pool.submit(remove)
         try:
-            assert not cleaned.wait(0.05)
+            assert cleanup_started.wait(5)
+            assert not cleaned.is_set()
         finally:
             release.set()
         work.result(timeout=5)
@@ -996,3 +1001,26 @@ def test_stream_cleanup_waits_for_native_work_and_rejects_late_work():
     assert events == ["native finished", "unloaded"]
     with pytest.raises(RuntimeError, match="stream has ended"):
         lifetime.run(lambda: pytest.fail("late work accessed unloaded model"))
+
+
+def test_stream_unload_is_single_shot_during_disconnect():
+    import threading
+    from concurrent.futures import ThreadPoolExecutor
+    from api.routers.dub_core import _ASRWorkLifetime
+    lifetime = _ASRWorkLifetime()
+    started, release = threading.Event(), threading.Event()
+    calls = []
+    def unload():
+        calls.append("unload")
+        assert len(calls) == 1
+        started.set()
+        assert release.wait(5)
+    with ThreadPoolExecutor(max_workers=2) as pool:
+        normal = pool.submit(lifetime.cleanup, unload)
+        assert started.wait(5)
+        lifetime.stop()
+        disconnected = pool.submit(lifetime.cleanup, unload)
+        release.set()
+        normal.result(timeout=5)
+        disconnected.result(timeout=5)
+    assert calls == ["unload"]