Drain all queued tasks on agent startup (loop until empty)

Task 3 from pr-21-fixes.md:

- _lifespan startup poll now loops calling next_task() until it returns None,
  processing each task before moving to the next; previously only one task
  was claimed, leaving N-1 accumulated tasks permanently stuck
- New test: startup poll with 3 queued tasks drains all 3 before yield

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: coordt

agents/issue-triage/issue_triage/agent.py

@@ -73,13 +73,20 @@ async def _poll_and_process(client: ForemanClient) -> None:
 
 @asynccontextmanager
 async def _lifespan(application: FastAPI) -> AsyncIterator[None]:
-    """FastAPI lifespan: startup poll for tasks queued while the agent was down.
+    """FastAPI lifespan: drain all tasks queued while the agent was down.
+
+    Loops calling next_task() until the queue is empty so that accumulated
+    pending tasks are not left stuck after an unclean restart.
 
     Args:
         application: The FastAPI application instance.
     """
     client = _get_client(application)
-    await _poll_and_process(client)
+    while True:
+        task = await asyncio.to_thread(client.next_task)
+        if task is None:
+            break
+        await _process_task(client, task)
     yield
     client.close()
 

tests/test_agent_server.py

@@ -141,12 +141,29 @@ def test_next_task_returning_task_calls_complete(
 
 
 class TestStartupPoll:
-    """Lifespan startup poll fires next_task() once on boot."""
+    """Lifespan startup poll drains all queued tasks on boot."""
 
-    def test_startup_poll_calls_next_task_once(self, mock_foreman_client: MagicMock) -> None:
-        """Lifespan startup poll calls client.next_task() exactly once."""
+    def test_startup_poll_calls_next_task_once_when_queue_empty(self, mock_foreman_client: MagicMock) -> None:
+        """Startup poll calls next_task() once when the queue is empty (returns None)."""
         app.state.client = mock_foreman_client
         with TestClient(app):
             pass
         del app.state.client
         assert mock_foreman_client.next_task.call_count == 1
+
+    def test_startup_poll_drains_all_queued_tasks(self, mock_foreman_client: MagicMock, mocker) -> None:
+        """Startup poll loops until next_task() returns None, processing each task."""
+        tasks = [_make_task(f"t{i}") for i in range(3)]
+        mock_foreman_client.next_task.side_effect = [*tasks, None]
+        stub_decision = MagicMock()
+        mocker.patch("agent.triage", return_value=stub_decision)
+
+        app.state.client = mock_foreman_client
+        with TestClient(app):
+            pass
+        del app.state.client
+
+        # next_task called 4 times: 3 tasks + 1 None to break the loop
+        assert mock_foreman_client.next_task.call_count == 4
+        # All 3 tasks completed
+        assert mock_foreman_client.complete_task.call_count == 3