fix: remove extra_body tool_choice hack for Claude backend

PydanticAI handles tool_choice natively for Anthropic. The extra_body
hack caused an infinite tool call loop where Claude kept calling the
same tool because tool_choice was forced to "any".

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/agents/tatlock.py

@@ -494,13 +494,13 @@ class TatlockAgent(AgentInterface):
                 )
 
         # Run with scoped tools and tracker
-        # Force tool_choice: required to make LLM actually call tools
-        from pydantic_ai.settings import ModelSettings
+        # Force tool_choice to make LLM actually call tools
+        from src.anthropic.model_selector import get_tool_choice_settings
         result = await scoped_agent.run(
             enriched_message,
             message_history=pydantic_history if pydantic_history else None,
             deps=tool_tracker,
-            model_settings=ModelSettings(extra_body={"tool_choice": "required"})
+            model_settings=get_tool_choice_settings(),
         )
 
         logger.info(
@@ -624,7 +624,6 @@ class TatlockAgent(AgentInterface):
                 - tool_outputs: Dict mapping tool names to their outputs
                 - raw_output: The agent's raw text output
         """
-        from pydantic_ai.settings import ModelSettings
         from pydantic_ai.messages import (
             ModelRequest,
             ModelResponse,
@@ -684,11 +683,12 @@ class TatlockAgent(AgentInterface):
                 )
 
         # Run with scoped tools and tracker
+        from src.anthropic.model_selector import get_tool_choice_settings
         result = await scoped_agent.run(
             enriched_message,
             message_history=pydantic_history if pydantic_history else None,
             deps=tool_tracker,
-            model_settings=ModelSettings(extra_body={"tool_choice": "required"})
+            model_settings=get_tool_choice_settings(),
         )
 
         # Extract tool calls and results from the agent's messages

src/anthropic/__init__.py

@@ -7,11 +7,13 @@ Provides model selection with automatic fallback between Claude and Ollama.
 from src.anthropic.model_selector import (
     check_claude_health,
     get_model,
+    get_tool_choice_settings,
     is_claude_available,
 )
 
 __all__ = [
     "check_claude_health",
     "get_model",
+    "get_tool_choice_settings",
     "is_claude_available",
 ]

src/anthropic/model_selector.py

@@ -132,6 +132,23 @@ def get_model(prefer_cloud: bool | None = None) -> Union[AnthropicModel, OpenAIC
     )
 
 
+def get_tool_choice_settings() -> 'ModelSettings':
+    """
+    Get model_settings for forcing tool calls on the first request.
+
+    For Claude: PydanticAI handles tool_choice natively, so no extra_body needed.
+    For Ollama: Pass tool_choice="required" via extra_body to force tool calling.
+    """
+    from pydantic_ai.settings import ModelSettings
+
+    if is_claude_available() and config.PREFER_CLOUD_BACKEND:
+        # PydanticAI's Anthropic model handles tool_choice internally
+        return ModelSettings()
+    else:
+        # Ollama needs explicit tool_choice via extra_body
+        return ModelSettings(extra_body={"tool_choice": "required"})
+
+
 def get_model_info() -> dict:
     """
     Get information about the current model configuration.