infrastructure-pydantic-validation--litellm-1-82-0-complexity-router-fails-with-pydant-ca584440

THEN Edit `litellm/types/router.py` and change the type of `messages` in `PreRoutingHookResponse` from `List[Dict[str, str]]` to `List[Dict[str, Any]]`. Also add `Any` to the typing imports (if not already present). This allows message content that is a list of content blocks (as per Anthropic's API) to pass Pydantic validation.

// In litellm/types/router.py, change:
class PreRoutingHookResponse(BaseModel):
    messages: List[Dict[str, str]]  # old

// To:
from typing import Any
class PreRoutingHookResponse(BaseModel):
    messages: List[Dict[str, Any]]  # new