Persist in-progress chat sessions

tests/test_gui_server.py

@@ -17,6 +17,7 @@ from pathlib import Path
 from fastapi.testclient import TestClient
 
 from backend.api.server import AgentState, create_app
+from src.agent_types import AgentRunResult
 from src.session_store import StoredAgentSession, load_agent_session, save_agent_session
 
 
@@ -161,6 +162,53 @@ class GuiServerTests(unittest.TestCase):
             payload = response.json()
             self.assertIsNone(payload['session_id'])
 
+    def test_chat_persists_in_progress_session_before_agent_finishes(self) -> None:
+        with tempfile.TemporaryDirectory() as d:
+            root = Path(d)
+            client, state = _build_client(root)
+            agent = state.agent_for('alice')
+
+            def fake_run(
+                prompt: str,
+                session_id: str | None = None,
+                *,
+                runtime_context: str | None = None,
+                event_sink: object | None = None,
+            ) -> AgentRunResult:
+                stored = load_agent_session(
+                    'pending-1',
+                    directory=root / 'accounts' / 'alice' / 'sessions',
+                )
+                self.assertEqual(stored.session_id, 'pending-1')
+                self.assertEqual(stored.budget_state.get('status'), 'running')
+                self.assertEqual(stored.messages[-1]['role'], 'user')
+                self.assertEqual(stored.messages[-1]['content'], 'hello')
+                return AgentRunResult(
+                    final_output='done',
+                    turns=1,
+                    tool_calls=0,
+                    transcript=stored.messages
+                    + ({'role': 'assistant', 'content': 'done'},),
+                    session_id=session_id,
+                )
+
+            original_run = agent.run
+            agent.run = fake_run  # type: ignore[method-assign]
+            try:
+                response = client.post(
+                    '/api/chat',
+                    json={
+                        'prompt': 'hello',
+                        'account_id': 'alice',
+                        'session_id': ' pending-1 ',
+                    },
+                )
+            finally:
+                agent.run = original_run  # type: ignore[method-assign]
+
+            self.assertEqual(response.status_code, 200)
+            self.assertEqual(response.json()['session_id'], 'pending-1')
+
     def test_chat_uses_account_scoped_model_config(self) -> None:
         with tempfile.TemporaryDirectory() as d:
             client, _ = _build_client(Path(d))