fix(responses-converter): strip strict from function tools before engine dispatch

responses_api_models/vllm_model/app.py

@@ -467,6 +467,21 @@ def _resolve_audio_path_to_url(self, audio_path: str) -> str:
             encoded = base64.b64encode(f.read()).decode("ascii")
         return f"data:audio/{mime};base64,{encoded}"
 
+    @staticmethod
+    def _strip_hosted_only_tool_fields(body_dict: Dict[str, Any]) -> None:
+        """Remove OpenAI-hosted-only fields from function tool definitions.
+
+        ``strict`` is an OpenAI-hosted schema-enforcement flag that vLLM does
+        not implement: its FunctionDefinition keeps the unknown key, and chat
+        templates that render unknown function-definition keys (e.g.
+        Nemotron's ``render_extra_keys``) inject it into the prompt,
+        perturbing every tool-bearing request. Strip it at the vLLM boundary
+        so hosted providers keep their ``strict`` semantics.
+        """
+        for tool_dict in body_dict.get("tools") or []:
+            if tool_dict.get("type") == "function":
+                (tool_dict.get("function") or {}).pop("strict", None)
+
     def _preprocess_chat_completion_create_params(self, request: Request, body_dict: Dict[str, Any]) -> Dict[str, Any]:
         """Preprocess the body dict before issuing a chat completion request.
 
@@ -483,6 +498,8 @@ def _preprocess_chat_completion_create_params(self, request: Request, body_dict:
             The (possibly mutated) ``body_dict`` that will be forwarded to
             ``client.create_chat_completion``.
         """
+        self._strip_hosted_only_tool_fields(body_dict)
+
         if self.config.replace_developer_role_with_system:
             for message_dict in body_dict["messages"]:
                 if message_dict.get("role") == "developer":
@@ -1087,6 +1104,10 @@ async def _chat_completions_via_completions_api(
         modes — /v1/completions is text-only.
         """
         body_dict = body.model_dump(exclude_unset=True)
+        # This path never runs _preprocess_chat_completion_create_params, and
+        # _render_messages_via_chat_template hands tools to apply_chat_template,
+        # so hosted-only fields must be stripped here too.
+        self._strip_hosted_only_tool_fields(body_dict)
         messages = body_dict.get("messages", []) or []
         metadata = body_dict.get("metadata", {}) or {}
 

responses_api_models/vllm_model/tests/test_app.py

@@ -84,6 +84,22 @@ def lineage_index():
     return _TEST_LINEAGE.index
 
 
+def test_strip_hosted_only_tool_fields_pops_strict() -> None:
+    body_dict = {
+        "tools": [
+            {"type": "function", "function": {"name": "get_weather", "strict": True}},
+            {"type": "custom", "custom": {"name": "not_a_function"}},
+        ]
+    }
+    VLLMModel._strip_hosted_only_tool_fields(body_dict)
+    assert "strict" not in body_dict["tools"][0]["function"]
+    assert body_dict["tools"][0]["function"]["name"] == "get_weather"
+    assert body_dict["tools"][1] == {"type": "custom", "custom": {"name": "not_a_function"}}
+
+    # Tolerates absent tools.
+    VLLMModel._strip_hosted_only_tool_fields({})
+
+
 def test_transport_io_writer_keeps_full_payload(monkeypatch: MonkeyPatch, tmp_path) -> None:
     log_path = tmp_path / "model-io-transport.jsonl"
     monkeypatch.setenv("NEMO_GYM_VLLM_TRANSPORT_LOG", str(log_path))
@@ -965,7 +981,6 @@ def _standardize(messages: list) -> list:
                     "required": ["order_id"],
                 },
                 "description": "Get the current status for a given order",
-                "strict": True,
             },
             {
                 "name": "get_delivery_date",
@@ -980,7 +995,6 @@ def _standardize(messages: list) -> list:
                     "required": ["order_id"],
                 },
                 "description": "Get the estimated delivery date for a given order",
-                "strict": True,
             },
         ]
         assert expected_sent_tools == actual_sent_tools
@@ -1437,7 +1451,6 @@ def test_responses_multistep_multiturn(self, monkeypatch: MonkeyPatch):
                     },
                     "required": ["order_id", "date"],
                 },
-                "strict": True,
             }
         ]
         assert expected_sent_tools == actual_sent_tools