Default `anthropic-beta` feature set by AnthropicModel incompatible with other providers

[jerry-reevo]

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Description

Starting with pydantic-ai version 0.6.2 it seems that the AnthropicModel now sets anthropic-beta with code-execution-2025-05-22.

This seems to unintentionally introduce behavior changes to existing Anthropic agents and is not supported by all providers. This causes an AnthropicModel using the AsyncAnthropicVertex (for GCP VertexAI) to error out with:

pydantic_ai.exceptions.ModelHTTPError: status_code: 400, model_name: claude-sonnet-4@20250514, body: {'type': 'error', 'error': {'type': 'invalid_request_error', 'message': 'Unexpected value(s) `code-execution-2025-05-22` for the `anthropic-beta` header. Please consult our documentation at docs.anthropic.com or try again without the header.'}}

Workaround is to explicitly set anthropic-beta to an empty string, i.e. extra_headers={"anthropic-beta": ""}

Default is being set here: https://github.com/pydantic/pydantic-ai/blob/main/pydantic_ai_slim/pydantic_ai/models/anthropic.py#L268

Example Code

AnthropicModel(
    "claude-sonnet-4@20250514",
    provider=AnthropicProvider(
        anthropic_client=anthropic_vertex,  # type: ignore
    ),
    # This is now required for use with Vertex AI
    settings=AnthropicModelSettings(
        extra_headers={"anthropic-beta": ""},
    ),
)

Python, Pydantic AI & LLM client version

pydantic-ai 0.7.1
Python 3.12

[pydanticai-bot]

PydanticAI Github Bot Found 1 issues similar to this one:

1. "anthropic-beta and VertexAI #2512" (90% similar)

[jerry-reevo]

This is a duplicate of #2512