fix: fence self-heal worker registration against cancellation

(cherry picked from commit 0fb38b7b5c9453781353464ca5c48c7365359cf1)

tests/test_self_heal_worker_cancellation.py

@@ -0,0 +1,95 @@
+"""Cancellation must fence both credential self-heal constructors.
+
+Reuse the real worker/Stop fixture; only the external Agent and credential
+refresh are synthetic. No provider or tool operation is executed.
+"""
+import threading
+from concurrent.futures import ThreadPoolExecutor
+
+import pytest
+
+from api import config, streaming
+from tests.test_steer_worker_boundaries import worker_scene as worker_scene
+
+
+@pytest.mark.parametrize("failure_path", ["exception", "returned"])
+@pytest.mark.parametrize("cancellation", ["stop", "event-only", "detached-only", "none"])
+def test_self_heal_registration_obeys_retained_stop(worker_scene, monkeypatch, failure_path, cancellation):
+    scene = worker_scene
+    entered, release = threading.Event(), threading.Event()
+    created, interrupted, finalized = [], [], []
+
+    def on_init():
+        candidate = scene.agent
+        created.append(candidate)
+        original_interrupt = candidate.interrupt
+
+        def interrupt(reason):
+            interrupted.append(candidate)
+            return original_interrupt(reason)
+
+        candidate.interrupt = interrupt
+        if len(created) == 2:
+            entered.set()
+            assert release.wait(8), "self-heal constructor barrier timed out"
+
+    def on_run():
+        if len(created) == 1:
+            if failure_path == "exception":
+                raise RuntimeError("401 unauthorized")
+            scene.result = {"error": "401 unauthorized", "messages": []}
+        else:
+            scene.result = None
+
+    scene.on_init, scene.on_run = on_init, on_run
+    monkeypatch.setattr(streaming, "_attempt_credential_self_heal", lambda *args, **kwargs: {
+        "provider": "openai", "api_key": "synthetic-self-heal-fixture",
+        "base_url": "http://127.0.0.1:1/v1",
+    })
+    finalize = streaming._finalize_cancelled_turn
+
+    def observed_finalize(*args, **kwargs):
+        assert scene.lock.owner != threading.get_ident(), "finalize held STREAMS_LOCK"
+        finalized.append(True)
+        return finalize(*args, **kwargs)
+
+    monkeypatch.setattr(streaming, "_finalize_cancelled_turn", observed_finalize)
+    with ThreadPoolExecutor(max_workers=2) as pool:
+        stop_future = None
+        future = pool.submit(scene.run)
+        try:
+            assert entered.wait(8), "real worker did not enter credential self-healing"
+            assert len(created) == 2
+            retained = config.CANCEL_FLAGS["run"]
+            if cancellation == "stop":
+                # Stop can wait for the session lock after its atomic cancel
+                # edge. Do not block constructor release on that later write.
+                stop_future = pool.submit(streaming.cancel_stream, "run")
+                assert retained.wait(5), "Stop did not publish cancellation"
+                with config.STREAMS_LOCK:
+                    assert "run" not in config.STREAMS
+                    assert "run" not in config.CANCEL_FLAGS
+            elif cancellation == "event-only":
+                with config.STREAMS_LOCK:
+                    retained.set()
+                    config.CANCEL_FLAGS.pop("run")
+            elif cancellation == "detached-only":
+                with config.STREAMS_LOCK:
+                    config.STREAMS.pop("run")
+                assert not retained.is_set()
+        finally:
+            release.set()
+        future.result(timeout=12)
+        if stop_future is not None:
+            assert stop_future.result(timeout=12) is True
+
+    if cancellation == "none":
+        assert scene.calls.count("run") == 2, "valid credential refresh must still retry"
+    else:
+        assert scene.calls.count("run") == 1, "cancelled self-heal executed the replacement Agent"
+        cached = config.SESSION_AGENT_CACHE.get("original")
+        assert not cached or cached[0] is not created[-1], "cancelled replacement entered the reusable cache"
+        assert created[-1] in interrupted
+        assert finalized
+    assert "run" not in config.AGENT_INSTANCES
+    assert "run" not in config.ACTIVE_RUNS