fix(agent): chat() surfaces error instead of KeyError on no-final_response result

run_agent.py

@@ -5796,7 +5796,10 @@ def chat(self, message: str, stream_callback: Optional[callable] = None) -> str:
             str: Final assistant response
         """
         result = self.run_conversation(message, stream_callback=stream_callback)
-        return result["final_response"]
+        # run_conversation's error/failure return paths (API error after retries,
+        # billing/credits exhaustion, policy halt, etc.) omit "final_response";
+        # surface the error message instead of raising KeyError here.
+        return result.get("final_response") or result.get("error") or ""
 
     def _run_codex_app_server_turn(
         self,
@@ -5989,7 +5992,7 @@ def main(
     print(f"📞 API Calls: {result['api_calls']}")
     print(f"💬 Messages: {len(result['messages'])}")
 
-    if result['final_response']:
+    if result.get('final_response'):
         print("\n🎯 FINAL RESPONSE:")
         print("-" * 30)
         print(result['final_response'])

tests/test_chat_final_response_resilience.py

@@ -0,0 +1,41 @@
+"""Regression: AIAgent.chat() must not crash when run_conversation returns an
+error/failure result that omits the 'final_response' key.
+
+Several error/failure return paths in agent.conversation_loop.run_conversation
+(API error after max retries, billing/credits exhaustion, policy halt, etc.)
+return a result dict with keys like {messages, completed, api_calls, error,
+failed} but *no* 'final_response'. chat() previously did
+``return result["final_response"]`` and raised ``KeyError: 'final_response'``
+on those paths instead of surfacing the error.
+"""
+
+
+def _agent_with(result):
+    # Bypass the heavy __init__; chat() only depends on self.run_conversation.
+    from run_agent import AIAgent
+
+    agent = AIAgent.__new__(AIAgent)
+    agent.run_conversation = lambda *a, **k: result
+    return agent
+
+
+def test_chat_surfaces_error_when_final_response_missing():
+    agent = _agent_with({
+        "messages": [],
+        "completed": False,
+        "api_calls": 1,
+        "error": "API call failed after 3 retries",
+        "failed": True,
+        # no "final_response" key — the regression case
+    })
+    assert agent.chat("hi") == "API call failed after 3 retries"
+
+
+def test_chat_returns_final_response_when_present():
+    agent = _agent_with({"final_response": "hello world", "error": None})
+    assert agent.chat("hi") == "hello world"
+
+
+def test_chat_empty_string_when_neither_final_response_nor_error():
+    agent = _agent_with({"completed": True, "messages": [], "api_calls": 0})
+    assert agent.chat("hi") == ""