fix(agent): run the outbound payload sanitizers on the summary request

Building the summary through `_build_api_kwargs` means it now carries
`tools`, but it still skipped the `_sanitize_structure_surrogates` /
`_force_ascii_payload` chokepoint the main loop applies after building
(turn_api_request). On cache-planned routes the main loop scrubs a deep
copy of the tools, so `agent.tools` can still hold a lone surrogate that
providers reject with a non-retryable 400 (#50959 class) — a request the
tool-less summary never used to make. Apply the same two passes here.

agent/chat_completion_helpers.py

@@ -38,7 +38,8 @@ from agent.model_metadata import is_local_endpoint
 from agent.message_content import flatten_message_text
 from agent.message_metadata import append_message, stamp_message_timestamp
 from agent.message_sanitization import (
-    _sanitize_surrogates, _repair_tool_call_arguments, normalize_finish_reason as _normalize_finish_reason,
+    _sanitize_structure_non_ascii, _sanitize_structure_surrogates, _sanitize_surrogates,
+    _repair_tool_call_arguments, normalize_finish_reason as _normalize_finish_reason,
 )
 from agent.reasoning_summaries import append_streamed_reasoning_detail, separate_glued_reasoning_blocks
 from agent.stream_single_writer import claim_stream_writer, stream_writer_is_current
@@ -2055,6 +2056,12 @@ def _chat_summary_attempt(agent, api_messages: list, api_request_id: str):
     # tool_choice="none": SGLang removes tools from its rendered prompt in that
     # mode, which would invalidate the cached prefix this path is preserving.
     summary_kwargs = agent._build_api_kwargs(api_messages)
+    # Same outbound chokepoint as turn_api_request: the summary now carries ``tools``, and on
+    # cache-planned routes the main loop scrubbed a deep copy, so ``agent.tools`` may still hold
+    # the lone surrogates / non-ASCII bytes the provider 400s on (#50959 class).
+    _sanitize_structure_surrogates(summary_kwargs)
+    if agent._force_ascii_payload:
+        _sanitize_structure_non_ascii(summary_kwargs)
 
     def _attempt(retry_count: int) -> str:
         summary_client = agent._ensure_primary_openai_client(reason="iteration_limit_summary_retry" if retry_count else "iteration_limit_summary")

tests/agent/test_run_agent.py

@@ -2808,6 +2808,23 @@ class TestHandleMaxIterations:
         assert all(summary["model"] == ordinary["model"] for summary in summaries)
         assert all(summary["messages"][0] == ordinary["messages"][0] for summary in summaries)
 
+    def test_summary_request_scrubs_surrogates_in_tool_schema(self, agent):
+        """The summary rides the same outbound surrogate chokepoint as the main loop (#50959 class)."""
+        agent.client.chat.completions.create.return_value = _mock_response(content="Summary")
+        agent._cached_system_prompt = "You are helpful."
+        agent.tools = [{"type": "function", "function": {
+            "name": "web_search", "description": "lone surrogate \ud83d here",
+            "parameters": {"type": "object", "properties": {}},
+        }}]
+
+        result = agent._handle_max_iterations([{"role": "user", "content": "do stuff"}], 60)
+
+        assert result == "Summary"
+        sent = agent.client.chat.completions.create.call_args.kwargs
+        description = sent["tools"][0]["function"]["description"]
+        assert "\ud83d" not in description
+        description.encode("utf-8")  # a provider serializes this; lone surrogates raise here
+
     def test_summary_tool_call_only_response_retries_once(self, agent):
         """A tool-only summary is scrubbed to empty and receives one retry."""
         agent.client.chat.completions.create.side_effect = [