fix(agent): drop terminal empty-response sentinels

run_agent.py

@@ -3792,18 +3792,21 @@ class AIAgent:
 
         Ensures conversations are never lost, even on errors or early returns.
         """
-        self._drop_trailing_empty_recovery_synthetic(messages)
+        self._drop_trailing_empty_response_scaffolding(messages)
         self._apply_persist_user_message_override(messages)
         self._session_messages = messages
         self._save_session_log(messages)
         self._flush_messages_to_session_db(messages, conversation_history)
 
-    def _drop_trailing_empty_recovery_synthetic(self, messages: List[Dict]) -> None:
+    def _drop_trailing_empty_response_scaffolding(self, messages: List[Dict]) -> None:
-        """Remove private empty-response retry scaffolding from transcript tails."""
+        """Remove private empty-response retry/failure scaffolding from transcript tails."""
         while (
             messages
             and isinstance(messages[-1], dict)
-            and messages[-1].get("_empty_recovery_synthetic")
+            and (
+                messages[-1].get("_empty_recovery_synthetic")
+                or messages[-1].get("_empty_terminal_sentinel")
+            )
         ):
             messages.pop()
 
@@ -13828,9 +13831,15 @@ class AIAgent:
                         # "(empty)" terminal.
                         _turn_exit_reason = "empty_response_exhausted"
                         reasoning_text = self._extract_reasoning(assistant_message)
-                        self._drop_trailing_empty_recovery_synthetic(messages)
+                        self._drop_trailing_empty_response_scaffolding(messages)
                         assistant_msg = self._build_assistant_message(assistant_message, finish_reason)
                         assistant_msg["content"] = "(empty)"
+                        # This is a user-facing failure sentinel for the gateway,
+                        # not real assistant content. Persisting it makes later
+                        # "continue" turns replay assistant("(empty)") as if it
+                        # were a meaningful model response, which can keep long
+                        # tool-heavy sessions stuck in empty-response loops.
+                        assistant_msg["_empty_terminal_sentinel"] = True
                         messages.append(assistant_msg)
 
                         if reasoning_text:
@@ -13913,6 +13922,7 @@ class AIAgent:
                         and (
                             messages[-1].get("_thinking_prefill")
                             or messages[-1].get("_empty_recovery_synthetic")
+                            or messages[-1].get("_empty_terminal_sentinel")
                         )
                     ):
                         messages.pop()
@@ -14004,7 +14014,11 @@ class AIAgent:
         # Clean up VM and browser for this task after conversation completes
         self._cleanup_task_resources(effective_task_id)
 
-        # Persist session to both JSON log and SQLite
+        # Persist session to both JSON log and SQLite only after private retry
+        # scaffolding has been removed. Otherwise a later user "continue" turn
+        # can replay assistant("(empty)") / recovery nudges and fall into the
+        # same empty-response loop again.
+        self._drop_trailing_empty_response_scaffolding(messages)
         self._persist_session(messages, conversation_history)
 
         # ── Turn-exit diagnostic log ─────────────────────────────────────

tests/run_agent/test_empty_response_recovery_persistence.py

@@ -50,7 +50,7 @@ def test_persist_session_strips_trailing_empty_recovery_scaffolding():
     assert all(not msg.get("_empty_recovery_synthetic") for msg in messages)
 
 
-def test_persist_session_keeps_real_terminal_empty_response():
+def test_persist_session_keeps_unmarked_terminal_empty_response():
     agent = _agent_with_stubbed_persistence()
     messages = [
         {"role": "user", "content": "run the task"},
@@ -64,3 +64,21 @@ def test_persist_session_keeps_real_terminal_empty_response():
         {"role": "assistant", "content": "(empty)"},
     ]
     assert agent.saved_session_logs[-1] == messages
+
+
+def test_persist_session_strips_marked_terminal_empty_sentinel():
+    agent = _agent_with_stubbed_persistence()
+    messages = [
+        {"role": "user", "content": "continue"},
+        {
+            "role": "assistant",
+            "content": "(empty)",
+            "_empty_terminal_sentinel": True,
+        },
+    ]
+
+    AIAgent._persist_session(agent, messages, conversation_history=[])
+
+    assert messages == [{"role": "user", "content": "continue"}]
+    assert agent.saved_session_logs[-1] == messages
+    assert all(not msg.get("_empty_terminal_sentinel") for msg in messages)