Passing provider-specific kwargs — custom headers, org IDs, API versions

[gregorymazur26]

Some OpenAI API features require custom headers (e.g., OpenAI-Organization, OpenAI-Project). Anthropic has anthropic-beta headers for features like prompt caching. Azure OpenAI needs api-version in the URL.

How does LLMix handle provider-specific kwargs that don't map to the common config schema?

Our current workaround:

config = {
    "provider": "openai",
    "model": "gpt-4.1",
    "temperature": 0.3,
    # Provider-specific passthrough?
    "provider_kwargs": {
        "headers": {"OpenAI-Organization": "org-abc123"},
        "timeout": 120,
    },
}

Does provider_kwargs (or equivalent) exist? If so:

• Is it validated or passed through blindly?
• Does it merge with LLMix's internal headers or override them?
• For Azure, can we pass api_version and azure_endpoint here?

We're also interested in response header access. OpenAI returns x-ratelimit-remaining-tokens which would be useful for the AIMD semaphore to read directly rather than waiting for 429s. Is there a hook to inspect response headers?