Fix: Bridge-worker silently drops assistant replies from state.db (31269)

agent/conversation_loop.py

@@ -229,6 +229,30 @@ def _restore_or_build_system_prompt(agent, system_message, conversation_history)
             )
 
 
+def _ensure_final_response_in_messages(messages: list, final_response) -> None:
+    """Inject final_response into messages if it's a non-empty assistant reply
+    that isn't already represented by the tail message.
+
+    Several exit paths (partial_stream_recovery, fallback_prior_turn_content,
+    max_iterations) set final_response but break without appending a structured
+    assistant message dict.  The normal text_response path already appended at
+    ~L3833; skip re-injection when the tail already matches.
+    """
+    if (
+        final_response
+        and isinstance(final_response, str)
+        and final_response.strip()
+        and final_response != "(empty)"
+    ):
+        _tail = messages[-1] if messages else None
+        if not (
+            isinstance(_tail, dict)
+            and _tail.get("role") == "assistant"
+            and _tail.get("content") == final_response
+        ):
+            messages.append({"role": "assistant", "content": final_response})
+
+
 def run_conversation(
     agent,
     user_message: str,
@@ -3960,6 +3984,9 @@ def _stop_spinner():
     # can replay assistant("(empty)") / recovery nudges and fall into the
     # same empty-response loop again.
     agent._drop_trailing_empty_response_scaffolding(messages)
+
+    _ensure_final_response_in_messages(messages, final_response)
+
     agent._persist_session(messages, conversation_history)
 
     # ── Turn-exit diagnostic log ─────────────────────────────────────

tests/run_agent/test_bridge_assistant_persist.py

@@ -0,0 +1,114 @@
+"""Regression tests for #31269 — bridge-worker silently drops assistant replies.
+
+The fix ensures `final_response` is injected into the messages list before
+`_persist_session()` when exit paths like partial_stream_recovery or
+max_iterations set final_response without appending a structured assistant
+message dict.
+"""
+
+from unittest.mock import MagicMock, patch, PropertyMock
+import pytest
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+def _make_agent(messages=None, final_response="Hello!"):
+    """Build a minimal mock agent with the attributes run_conversation uses."""
+    agent = MagicMock()
+    agent.messages = messages or [
+        {"role": "user", "content": "hi"},
+    ]
+    agent.model = "test-model"
+    agent.tools = []
+    agent.provider = MagicMock()
+    agent.provider.model = "test-model"
+    agent._last_flushed_db_idx = 0
+    agent._session_db = MagicMock()
+    agent._drop_trailing_empty_response_scaffolding = MagicMock()
+    agent._persist_session = MagicMock()
+    return agent
+
+
+# ---------------------------------------------------------------------------
+# Tests
+# ---------------------------------------------------------------------------
+
+class TestFinalResponseInjectionBeforePersist:
+    """Verify assistant message is injected when missing from messages."""
+
+    def test_final_response_injected_when_messages_has_no_assistant(self):
+        """If messages only has user msg and final_response is set, assistant
+        should be appended before _persist_session."""
+        import agent.conversation_loop as cl
+
+        messages = [{"role": "user", "content": "hello"}]
+        agent = _make_agent(messages=messages)
+
+        # Simulate the tail of run_conversation: drop scaffolding, then persist.
+        with patch.object(cl, "final_response", "Hello from assistant", create=True):
+            # Directly test the injection logic
+            cl._ensure_final_response_in_messages(messages, "Hello from assistant")
+
+        assert messages[-1]["role"] == "assistant"
+        assert messages[-1]["content"] == "Hello from assistant"
+
+    def test_no_duplicate_when_assistant_already_present(self):
+        """If messages tail already has the assistant response, don't re-inject."""
+        import agent.conversation_loop as cl
+
+        messages = [
+            {"role": "user", "content": "hello"},
+            {"role": "assistant", "content": "Hello from assistant"},
+        ]
+        original_len = len(messages)
+
+        cl._ensure_final_response_in_messages(messages, "Hello from assistant")
+
+        assert len(messages) == original_len
+
+    def test_empty_final_response_not_injected(self):
+        """Empty or whitespace-only final_response should NOT be injected."""
+        import agent.conversation_loop as cl
+
+        messages = [{"role": "user", "content": "hello"}]
+
+        cl._ensure_final_response_in_messages(messages, "   ")
+
+        assert len(messages) == 1
+
+    def test_placeholder_empty_not_injected(self):
+        """The '(empty)' placeholder should NOT be injected."""
+        import agent.conversation_loop as cl
+
+        messages = [{"role": "user", "content": "hello"}]
+
+        cl._ensure_final_response_in_messages(messages, "(empty)")
+
+        assert len(messages) == 1
+
+    def test_non_string_final_response_not_injected(self):
+        """Non-string final_response (e.g. None) should not be injected."""
+        import agent.conversation_loop as cl
+
+        messages = [{"role": "user", "content": "hello"}]
+
+        cl._ensure_final_response_in_messages(messages, None)
+
+        assert len(messages) == 1
+
+    def test_different_assistant_tail_still_injects(self):
+        """If messages tail is an assistant message but with DIFFERENT content,
+        the new final_response should still be injected."""
+        import agent.conversation_loop as cl
+
+        messages = [
+            {"role": "user", "content": "hello"},
+            {"role": "assistant", "content": "old response"},
+        ]
+
+        cl._ensure_final_response_in_messages(messages, "new response")
+
+        assert messages[-1]["content"] == "new response"
+        assert messages[-2]["content"] == "old response"