Clear the SSE event log on every worker start, including Retry failed.

Resume reused the previous pipeline_complete, so the UI closed the stream and showed no live log while U19 was still reviewing.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/pipeline_worker.py

@@ -81,10 +81,12 @@ async def _run() -> None:
     # are visible to any API instance tailing the event log.
     pipeline_svc.set_broker(event_bridge.GCSEventBroker(storage, user_id))
 
-    # Fresh runs wipe the prior event log so the SSE consumer doesn't
-    # mix old events into the new run. Resume keeps the prior log so
-    # users see the full history.
-    if not resume:
+    # Always wipe the prior event log. Reprocess uses resume=True, and
+    # the old log still contains ``pipeline_complete``; the SSE tail
+    # would stop there and the UI would show a finished run with no live
+    # log while the worker is still reviewing. Pause-resume also hits a
+    # terminal ``pipeline_paused``. A fresh seq from 0 is the only safe
+    # option — completed_review_refs still skip paid ICs.
     pipeline_svc.broker.clear_history(project_id)
 
     if mode == "run":

tests/test_event_bridge.py

@@ -0,0 +1,24 @@
+"""GCS event log: a new run must not replay a prior pipeline_complete."""
+
+from backend.services.event_bridge import GCSEventBroker
+
+
+def test_clear_history_wipes_terminal_events(tmp_path):
+    from backend.services.storage import LocalStorageBackend
+
+    storage = LocalStorageBackend(tmp_path)
+    broker = GCSEventBroker(storage, "local")
+    broker.publish("p1", "step_update", {"stage": "validation"})
+    broker.publish("p1", "pipeline_complete", {"summary": {}})
+
+    prefix = "users/local/projects/p1/events/"
+    assert len(storage.list_prefix(prefix)) == 2
+
+    broker.clear_history("p1")
+    assert storage.list_prefix(prefix) == []
+
+    broker.publish("p1", "step_update", {"stage": "bom_parse"})
+    keys = storage.list_prefix(prefix)
+    assert len(keys) == 1
+    assert keys[0].endswith("0000000000.json")
+    assert storage.read_json(keys[0])["event"] == "step_update"