Disable use of tool_choice=required for deepseek-reasoner (#3644)

Author: ZeroAurora

pydantic_ai_slim/pydantic_ai/providers/deepseek.py

@@ -53,6 +53,8 @@ def model_profile(self, model_name: str) -> ModelProfile | None:
             openai_chat_thinking_field='reasoning_content',
             # Starting from DeepSeek v3.2, DeepSeek requires sending thinking parts for optimal agentic performance.
             openai_chat_send_back_thinking_parts='field',
+            # DeepSeek v3.2 reasoning mode does not support tool_choice=required yet
+            openai_supports_tool_choice_required=(model_name != 'deepseek-reasoner'),
         ).update(profile)
 
     @overload