Support anthropic skills

[mattbrandman]

Description

Add support for native and custom anthropic skills via API as documented here. I think it’s mainly an addition to the code interpreter built in tool https://docs.claude.com/en/api/skills-guide

References

No response

[DouweM]

@mattbrandman OK so this feature requires the following things:

1. Somehow let users specify skills to be passed to the API as container.skills with the skills-2025-10-02 beta header
2. Store response.container.id (likely on ModelResponse.provider_metadata) and pass it in again when continuing a run (https://docs.claude.com/en/api/skills-guide#multi-turn-conversations)
3. Handle pause_turn (https://docs.claude.com/en/api/skills-guide#long-running-operations): Fix Anthropic pause_turn handling to allow agent continuation #3051
4. Handle the bash_code_execution_tool_result event type (https://docs.claude.com/en/api/skills-guide#downloading-generated-files), store the result in ModelResponse, and make sure generated file_ids can be read easily.
   1. It looks like this is a newer version of the code execution tool than the one we currently support: https://docs.claude.com/en/docs/agents-and-tools/tool-use/code-execution-tool.

It makes sense to me to consider this a feature of the CodeExecutionTool as you suggest; since it's so Anthropic specific, I think it should be a new anthropic_skills field that takes their own skill objects.

I don't think we need to concern ourselves with creating skills or uploading files into a container.

Regarding handling generated files: OpenAI Code Interpreter can generate images that we turn into a FilePart with BinaryContent in ModelResponse.parts (see second example at https://ai.pydantic.dev/builtin-tools/#usage_1), but in this case we don't get the actual file binary content, just a file ID. So it wouldn't make sense to make that a FilePart, unless we automatically download the file which could be unexpected. So until we have a native way to represent uploaded files (#2574) the file IDs would only be available on the BuiltinToolReturnPart.content, which is annoying but better than nothing. It'd require similar logic to get the ID as the extract_file_ids function in Anthropic's examples.

@mattbrandman Would you be up for working on this? :)

[mattbrandman]

@DouweM i definitely would be! Don't have a ton of time as I have a few other pressing projects but if they wrap up when I hope could potentially tackle late this month early next.

[chetanreddyv]

@DouweM @mattbrandman I would love to work on this, it will be my First Issue. Hope its fine?

[mattbrandman]

Don't have to ask me I'm not a maintainer :) also generally I think the attitude of this project (and most OSS i've been involved in) has been always feel free to make a PR!

[DouweM]

@chetanreddyv Feel free to work on this, but be warned that for your first issue I would have recommended picking something simpler 😄 I'll gladly review your PR either way, but I'd expect this one to be a lot easier for someone who has more experience with the code base like @mattbrandman.