---
title: "Anthropic provider"
description: "Setting up and using Anthropic Claude (Opus, Sonnet, Haiku) in Cerevisor."
slug: guides/providers/anthropic
section: guides
subsection: providers
canonical_url: https://cerevisor.com/docs/guides/providers/anthropic
last_verified: 2026-05-18
last_verified_version: "1.2.0"
updated_at: 2026-05-18T15:08:18.053416+00:00
---

## Setup

You need an API key from [console.anthropic.com](https://console.anthropic.com).

1. **Settings → Providers → + Add provider → Anthropic.**
2. Paste your API key into the **API key** field.
3. Click **Test connection.** Cerevisor calls Anthropic's `/v1/models` endpoint to confirm the key works.
4. Click **Save.**

The key is stored in your OS keychain. It never lives in plain text on disk or in any `.cerevisor` file.

## Models

Cerevisor reads the live model list from `/v1/models` and surfaces it everywhere a model picker appears. The most-used Claude models you'll see:

| Model | Best for | Notes |
|---|---|---|
| **Claude Opus 4.x** | Highest quality, deepest reasoning. | Most expensive. Use for senior agents, complex synthesis, anything where quality is more important than cost. |
| **Claude Sonnet 4.x** | Balanced — strong quality at lower cost. | The default for most workloads. |
| **Claude Haiku 4.x** | Fastest, cheapest. | Great for reviewers, classifiers, simple transforms. |

Extended thinking variants (where applicable) are shown separately in the picker.

## Cost

Cerevisor reads token usage from each response and multiplies by the per-model pricing table. The status bar shows running cost during a run; the audit log saves the breakdown.

Per-token prices update as Anthropic releases new models. Cerevisor's pricing table is hardcoded. If you see costs that look stale after a model launch, restart Cerevisor (the table is loaded at startup) or wait for the next release.

## Default model

In the Library entry, you can set a **default model** for this provider. When an agent's model preference is **(auto)**, it falls back to this default.

## Headers and behavior

Cerevisor uses the official `@anthropic-ai/sdk`. Standard retry semantics, prompt caching (when supported), tool use, and vision are all wired through automatically.

Prompt caching is enabled by default when the API and the model support it; this can substantially reduce cost for workflows with shared context (e.g. multi-agent workflows reading the same project folder).

## Common errors

| Error | What it means | Fix |
|---|---|---|
| **401 Unauthorized** | Invalid API key. | Re-check the key. Generate a new one in the Anthropic console if needed. |
| **429 Rate limited** | You hit your account's rate limit. | Wait and retry, or upgrade your Anthropic plan. |
| **Network error** | Anthropic is unreachable. | Check your network. Cerevisor retries automatically with backoff. |