openai: fix tool_call param construction for SDK >=1.99; update KnownModelName with gpt-5-chat-latest (prefixed and bare)

Author: zachmayer

pydantic_ai_slim/pydantic_ai/models/__init__.py

@@ -307,6 +307,15 @@
         'openai:gpt-5-2025-08-07',
         'openai:gpt-5-mini-2025-08-07',
         'openai:gpt-5-nano-2025-08-07',
+        'openai:gpt-5-chat-latest',
+        'gpt-5-chat-latest',
+        'gpt-5',
+        'gpt-5-mini',
+        'gpt-5-nano',
+        'gpt-5-2025-08-07',
+        'gpt-5-mini-2025-08-07',
+        'gpt-5-nano-2025-08-07',
+        'gpt-5-chat-latest',
         'openai:o1',
         'openai:o1-2024-12-17',
         'openai:o1-mini',

pydantic_ai_slim/pydantic_ai/models/openai.py

@@ -505,11 +505,13 @@ async def _map_messages(self, messages: list[ModelMessage]) -> list[chat.ChatCom
 
     @staticmethod
     def _map_tool_call(t: ToolCallPart) -> chat.ChatCompletionMessageToolCallParam:
-        return chat.ChatCompletionMessageToolCallParam(
-            id=_guard_tool_call_id(t=t),
-            type='function',
-            function={'name': t.tool_name, 'arguments': t.args_as_json_str()},
-        )
+        # openai>=1.99 changed these Param classes to typing.Union aliases;
+        # construct as a plain dict compatible with the union instead of instantiating.
+        return {
+            'id': _guard_tool_call_id(t=t),
+            'type': 'function',
+            'function': {'name': t.tool_name, 'arguments': t.args_as_json_str()},
+        }
 
     def _map_json_schema(self, o: OutputObjectDefinition) -> chat.completion_create_params.ResponseFormat:
         response_format_param: chat.completion_create_params.ResponseFormatJSONSchema = {  # pyright: ignore[reportPrivateImportUsage]