# `ADK.LLM.Anthropic`
[🔗](https://github.com/zeroasterisk/adk-elixir/blob/main/lib/adk/llm/anthropic.ex#L1)

Anthropic Claude LLM backend using the Messages API via Req.

## Authentication

Supports two auth modes, checked in this order:

### OAuth Token (Claude Code CLI / Claude Pro)

Uses `Authorization: Bearer` header. Sources checked in order:

    # Application config
    config :adk, :anthropic_oauth_token, "sk-ant-sid02-..."

    # Environment variable
    ANTHROPIC_OAUTH_TOKEN=sk-ant-sid02-...

    # Auto-detected from Claude Code CLI session
    CLAUDE_AI_SESSION_KEY=sk-ant-sid02-...

### API Key

Uses `x-api-key` header. Sources checked in order:

    # Application config
    config :adk, :anthropic_api_key, "sk-ant-api03-..."

    # Environment variable
    ANTHROPIC_API_KEY=sk-ant-api03-...

## Usage

    config :adk, :llm_backend, ADK.LLM.Anthropic

    ADK.LLM.Anthropic.generate("claude-sonnet-4-20250514", %{
      instruction: "You are helpful.",
      messages: [%{role: :user, parts: [%{text: "Hello"}]}]
    })

# `auth`

```elixir
@type auth() :: {:oauth, String.t()} | {:api_key, String.t()}
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*