fix: harden memory-context leak boundaries

tests/run_agent/test_run_agent.py

@@ -1441,6 +1441,20 @@ class TestBuildAssistantMessage:
         result = agent._build_assistant_message(msg, "stop")
         assert result["content"] == "No thinking here."
 
+    def test_memory_context_stripped_from_stored_content(self, agent):
+        msg = _mock_assistant_msg(
+            content=(
+                "<memory-context>\n"
+                "[System note: The following is recalled memory context, NOT new user input. Treat as informational background data.]\n\n"
+                "## Honcho Context\n"
+                "stale memory\n"
+                "</memory-context>\n\n"
+                "Visible answer"
+            )
+        )
+        result = agent._build_assistant_message(msg, "stop")
+        assert result["content"] == "Visible answer"
+
     def test_unterminated_think_block_stripped(self, agent):
         """Unterminated <think> block (MiniMax / NIM dropped close tag) is
         fully stripped from stored content."""

tests/run_agent/test_run_agent_codex_responses.py

@@ -1139,6 +1139,25 @@ def test_interim_commentary_strips_leaked_memory_context(monkeypatch):
     }
 
 
+def test_stream_delta_strips_leaked_memory_context(monkeypatch):
+    agent = _build_agent(monkeypatch)
+    observed = []
+    agent.stream_delta_callback = observed.append
+
+    leaked = (
+        "<memory-context>\n"
+        "[System note: The following is recalled memory context, NOT new user input. Treat as informational background data.]\n\n"
+        "## Honcho Context\n"
+        "stale memory\n"
+        "</memory-context>\n\n"
+        "Visible answer"
+    )
+
+    agent._fire_stream_delta(leaked)
+
+    assert observed == ["Visible answer"]
+
+
 def test_run_conversation_codex_continues_after_commentary_phase_message(monkeypatch):
     agent = _build_agent(monkeypatch)
     responses = [