Providers¶

Provider selects one of two backends. Everything else about a provider — the endpoint, the auth mechanism, which request fields survive — follows from that choice.

pub enum Provider {
    Anthropic,
    AnthropicLocal,
    OpenAi,
    OpenAiCompatible,
    Gemini,
    Ollama,
}

The enum is #[non_exhaustive]: a match on it needs a _ arm, and new variants can arrive in a minor release.

Which provider uses which backend¶

Provider::is_anthropic() returns true for Anthropic and AnthropicLocal and false for the rest. That is the whole dispatch rule.

AnthropicLocal does not default to a local endpoint¶

AnthropicLocal is for a self-hosted Anthropic-compatible endpoint — an in-house proxy, a gateway, Claude Code Local. The wire format is identical to Cloud, which is why it shares the backend.

What it does not do is change the default endpoint. With base_url: None, Provider::AnthropicLocal sends to https://api.anthropic.com/v1/messages, exactly like Provider::Anthropic. Always set base_url when you use it.

The variant still matters: it documents intent, and it is the one to keep an eye on if a future release starts treating the two differently.

Feature support by backend¶

Everything in this table was checked against the request builders in src/client.rs and src/anthropic.rs.

The four entries in bold are the ones that surprise people, because the field exists, compiles, and does nothing. They are covered in What rtb-chat does not do.

The model name picks the adapter¶

On the genai backend, Provider decides which environment variable the key is written to — and nothing else. Routing is genai's, and genai routes on the model name:

The fallback is the trap. Provider::OpenAiCompatible with a model name like llama-3.1-70b-instruct does not go to your OpenAI-compatible endpoint. It goes to localhost, because the name matches nothing and Ollama is genai's catch-all:

provider error: Web call failed for model 'llama-3.1-70b-instruct (adapter: Ollama)'.
Cause: Reqwest error: error sending request for url (http://localhost:11434/api/chat)

If you need a specific adapter, name it with genai's namespace:: prefix — for example together::meta-llama/Llama-3-70b. That gets the routing right, but not the key: Provider::OpenAiCompatible writes Config::api_key to OPENAI_API_KEY, and each namespaced adapter reads its own variable (TOGETHER_API_KEY, GROQ_API_KEY), so the call fails with ApiKeyEnvNotFound unless you export that variable yourself. It still cannot change the endpoint, which is the underlying limitation.

Where the API key goes¶

The environment writes are process-wide and permanent for the life of the process. Read The genai backend puts your key in the process environment before building a second client.

Anthropic-direct request headers¶

Every Anthropic-direct call sends:

anthropic-version is a compile-time constant. There is no config field for it, so a Messages API feature gated behind a newer version string needs a crate release.