# Anthropic

> Run Everruns agents on Anthropic Claude models via the Messages API, with streaming, tool use, and extended thinking.

Source: <https://everruns.com/docs/providers/anthropic/>

Everruns runs agents on [Anthropic](https://www.anthropic.com/) Claude models through the Claude Messages API, mapping its provider-neutral messages, tools, and reasoning onto the Anthropic wire format.

## What you get

* **Claude Messages API** streaming.
* **Tool use** mapped to provider-neutral Everruns tools.
* **Extended thinking**: adaptive thinking on recent Claude families and budget-based thinking on older ones, with the chain-of-thought signature preserved across multi-turn conversations.
* **Prompt caching** via bounded `cache_control` breakpoints on stable, high-value sections of the request.

## Configure in Everruns

1. Go to **Settings** → **Providers** and click **Add provider**.
2. Choose **Anthropic**.
3. Paste your Anthropic API key. Get one from the [Anthropic Console](https://console.anthropic.com/).
4. Save. Everruns discovers available Claude models automatically.

## Models

Anthropic’s `/v1/models` endpoint returns capability metadata, which Everruns merges with its built-in model profiles. Hardcoded profiles take precedence for cost data; discovered data fills gaps for newer models.

`max_tokens` is required on every Anthropic request, so Everruns always resolves a value from the model profile (falling back to a safe default) and will retry once with a lower limit if a stale profile causes the provider to reject it.

Thinking counts toward `max_tokens`. When you set `max_tokens` yourself, Everruns preserves it as a hard limit on all generated tokens, including thinking. When the limit cannot accommodate thinking, the driver omits thinking rather than exceed the limit. On models that always think (Opus 5.5, Sonnet 5.5, Haiku 5.5, Fable 5.x), omitting it would run thinking at the provider’s default effort, so the driver keeps it and lowers the effort to `low` instead. A very small limit on those models can still be spent on thinking; give them room for the answer.

Claude models that always think (Opus 5.5, Sonnet 5.5, Haiku 5.5, Fable 5.x) always get an explicit effort: the model’s default when you choose none, and `low` when you choose `none`. These and the other adaptive-thinking models reject assistant prefill, so a conversation must end with a user or tool message.

## Links

* [Anthropic](https://www.anthropic.com/)
* [Anthropic Console](https://console.anthropic.com/)
* [`everruns-drivers` on crates.io](https://crates.io/crates/everruns-drivers), feature `anthropic`
* [Migrate between providers](https://everruns.com/docs/how-to/migrate-providers/)