fix(codex): enforce Copilot replay policy at dispatch

Reapply the endpoint-aware preflight after request and execution
middleware so no override can reintroduce a connection-scoped ID.

agent/codex_responses_adapter.py

@@ -600,7 +600,11 @@ def _chat_messages_to_responses_input(
 # Input preflight / validation
 # ---------------------------------------------------------------------------
 
-def _preflight_codex_input_items(raw_items: Any) -> List[Dict[str, Any]]:
+def _preflight_codex_input_items(
+    raw_items: Any,
+    *,
+    is_github_responses: bool = False,
+) -> List[Dict[str, Any]]:
     if not isinstance(raw_items, list):
         raise ValueError("Codex Responses input must be a list of input items.")
 
@@ -741,7 +745,11 @@ def _preflight_codex_input_items(raw_items: Any) -> List[Dict[str, Any]]:
                 "content": normalized_content,
             }
             item_id = item.get("id")
-            if isinstance(item_id, str) and item_id.strip():
+            if (
+                not is_github_responses
+                and isinstance(item_id, str)
+                and item_id.strip()
+            ):
                 stripped_id = item_id.strip()
                 if len(stripped_id) <= _MAX_RESPONSES_ITEM_ID_LENGTH:
                     normalized_item["id"] = stripped_id
@@ -816,6 +824,7 @@ def _preflight_codex_api_kwargs(
     api_kwargs: Any,
     *,
     allow_stream: bool = False,
+    is_github_responses: bool = False,
 ) -> Dict[str, Any]:
     if not isinstance(api_kwargs, dict):
         raise ValueError("Codex Responses request must be a dict.")
@@ -837,7 +846,10 @@ def _preflight_codex_api_kwargs(
         instructions = str(instructions)
     instructions = instructions.strip() or DEFAULT_AGENT_IDENTITY
 
-    normalized_input = _preflight_codex_input_items(api_kwargs.get("input"))
+    normalized_input = _preflight_codex_input_items(
+        api_kwargs.get("input"),
+        is_github_responses=is_github_responses,
+    )
 
     tools = api_kwargs.get("tools")
     normalized_tools = None

agent/conversation_loop.py

@@ -1167,7 +1167,11 @@ def run_conversation(
                 if agent._force_ascii_payload:
                     _sanitize_structure_non_ascii(api_kwargs)
                 if agent.api_mode == "codex_responses":
-                    api_kwargs = agent._get_transport().preflight_kwargs(api_kwargs, allow_stream=False)
+                    api_kwargs = agent._get_transport().preflight_kwargs(
+                        api_kwargs,
+                        allow_stream=False,
+                        is_github_responses=agent._is_copilot_url(),
+                    )
                 # Copilot x-initiator: the first API call of a user turn is
                 # marked "user" so Copilot bills a premium request; tool-loop
                 # follow-ups keep the default "agent" header (#3040).
@@ -1314,6 +1318,12 @@ def run_conversation(
                         _use_streaming = False
 
                 def _perform_api_call(next_api_kwargs):
+                    if agent.api_mode == "codex_responses":
+                        next_api_kwargs = agent._get_transport().preflight_kwargs(
+                            next_api_kwargs,
+                            allow_stream=False,
+                            is_github_responses=agent._is_copilot_url(),
+                        )
                     if _use_streaming:
                         return agent._interruptible_streaming_api_call(
                             next_api_kwargs, on_first_delta=_stop_spinner

agent/transports/codex.py

@@ -440,13 +440,23 @@ class ResponsesApiTransport(ProviderTransport):
             return False
         return True
 
-    def preflight_kwargs(self, api_kwargs: Any, *, allow_stream: bool = False) -> dict:
+    def preflight_kwargs(
+        self,
+        api_kwargs: Any,
+        *,
+        allow_stream: bool = False,
+        is_github_responses: bool = False,
+    ) -> dict:
         """Validate and sanitize Codex API kwargs before the call.
 
         Normalizes input items, strips unsupported fields, validates structure.
         """
         from agent.codex_responses_adapter import _preflight_codex_api_kwargs
-        return _preflight_codex_api_kwargs(api_kwargs, allow_stream=allow_stream)
+        return _preflight_codex_api_kwargs(
+            api_kwargs,
+            allow_stream=allow_stream,
+            is_github_responses=is_github_responses,
+        )
 
     def map_finish_reason(self, raw_reason: str) -> str:
         """Map Codex response.status to OpenAI finish_reason.

tests/agent/test_codex_responses_adapter.py

@@ -238,6 +238,27 @@ def test_preflight_codex_input_items_keeps_short_message_id():
     assert items[0]["id"] == _VALID_ITEM_ID
 
 
+def test_preflight_codex_input_items_drops_short_id_for_github_responses():
+    items = _preflight_codex_input_items(
+        [
+            {
+                "type": "message",
+                "role": "assistant",
+                "status": "in_progress",
+                "content": [{"type": "output_text", "text": "pong"}],
+                "id": _VALID_ITEM_ID,
+                "phase": "final_answer",
+            }
+        ],
+        is_github_responses=True,
+    )
+
+    assert "id" not in items[0]
+    assert items[0]["status"] == "in_progress"
+    assert items[0]["phase"] == "final_answer"
+    assert items[0]["content"] == [{"type": "output_text", "text": "pong"}]
+
+
 def test_preflight_codex_api_kwargs_drops_oversized_message_id_end_to_end():
     kwargs = _preflight_codex_api_kwargs(
         {

tests/agent/transports/test_codex_transport.py

@@ -181,6 +181,34 @@ class TestCodexBuildKwargs:
         message_item = next(item for item in kw["input"] if item.get("type") == "message")
         assert message_item["id"] == "msg_short_id"
 
+    def test_github_preflight_drops_id_reintroduced_by_request_override(self, transport):
+        injected = {
+            "type": "message",
+            "role": "assistant",
+            "status": "in_progress",
+            "content": [{"type": "output_text", "text": "pong"}],
+            "id": "stale_short",
+            "phase": "final_answer",
+        }
+        kw = transport.build_kwargs(
+            model="gpt-5.5",
+            messages=[{"role": "user", "content": "continue"}],
+            tools=[],
+            is_github_responses=True,
+            request_overrides={"input": [injected]},
+        )
+
+        preflight = transport.preflight_kwargs(
+            kw,
+            is_github_responses=True,
+        )
+
+        message_item = preflight["input"][0]
+        assert "id" not in message_item
+        assert message_item["status"] == "in_progress"
+        assert message_item["phase"] == "final_answer"
+        assert message_item["content"] == [{"type": "output_text", "text": "pong"}]
+
     def test_non_github_responses_keeps_message_item_id_end_to_end(self, transport):
         messages = [
             {"role": "system", "content": "You are Hermes."},