Anthropic provider

Standalone — usable in any Node project, no @warlock.js/core required.

@warlock.js/ai-anthropic is the Anthropic provider adapter for @warlock.js/ai. It wraps the official @anthropic-ai/sdk Messages API and hands you a vendor-neutral ModelContract — the same shape every agent, workflow, and supervisor already speaks. Swap Claude in for any other provider without touching your orchestration code.

Install

npm

npm install @warlock.js/ai @warlock.js/ai-anthropic

yarn

yarn add @warlock.js/ai @warlock.js/ai-anthropic

pnpm

pnpm add @warlock.js/ai @warlock.js/ai-anthropic

Construct

One AnthropicSDK holds one live Anthropic client. Build it once at boot and reuse it everywhere — every model it produces shares the same connection pool, auth, and rate-limit state.

import { AnthropicSDK } from "@warlock.js/ai-anthropic";

const anthropic = new AnthropicSDK({
  apiKey: process.env.ANTHROPIC_API_KEY!,
});

The config extends the upstream ClientOptions, so anything the SDK accepts works here too — most usefully baseURL to point at a gateway or proxy, and provider to relabel the upstream (it defaults to "anthropic" and flows through to AgentReport.model, logs, and any provider-aware middleware).

const anthropic = new AnthropicSDK({
  apiKey: process.env.ANTHROPIC_API_KEY!,
  baseURL: "https://my-gateway.internal/anthropic",
  provider: "anthropic-gateway",
});

First call

Build a model, hand it to an agent, run it. execute() never throws — failures land in error as a typed AIError.

import { ai } from "@warlock.js/ai";
import { AnthropicSDK } from "@warlock.js/ai-anthropic";

const anthropic = new AnthropicSDK({ apiKey: process.env.ANTHROPIC_API_KEY! });

const assistant = ai.agent({
  model: anthropic.model({ name: "claude-sonnet-4-6" }),
  systemPrompt: "You are a concise senior TypeScript engineer.",
});

const { text, usage, error } = await assistant.execute("Why use generics?");

if (error) {
  console.warn(error.code, error.category);
} else {
  console.log(text, usage.total);
}

Use as a model

const model = anthropic.model({ name: "claude-sonnet-4-6", temperature: 0.7 });
// Pass to any @warlock.js/ai agent / workflow / supervisor.

Anthropic requires a token cap on every request. When you don’t set maxTokens (per-model or per-call), the adapter falls back to a generous default of 4096 so a caller who never thought about caps still gets a complete answer instead of a 400.

Capabilities

• Tool calling — vendor-neutral ToolConfigs map to Claude tool_use blocks; tool results round-trip back as user turns.
• Streaming — stream() yields text deltas, a tool-call once a tool_use block’s arguments have fully accumulated, and a terminal done carrying the final finish reason and usage.
• Structured output — on by default. A root-object JSON Schema is forwarded to Claude’s native output_config.format (JSON-schema structured outputs). Non-object schemas or a structuredOutput: false override fall back to the agent’s soft system-prompt hint plus client-side validation.
• Vision — auto-detected from the model name. Every Claude 3, 3.5/3.7, and 4 family model is treated as multimodal (prefixes claude-3, claude-4, claude-opus-4, claude-sonnet-4, claude-haiku-4); pre-3 families (claude-2, claude-instant) are text-only. Override either way with the vision flag.
• No embedder. Anthropic ships no first-party embeddings API, so this adapter has no embedder(). Pair Claude with an embedding provider — OpenAI, Google, Bedrock, or Ollama — when you need vectors.

Image attachments accept both a remote url and inlined base64 bytes (image/jpeg, image/png, image/gif, image/webp).

Vision

Pass image parts on a user message — the agent resolves attachments before they reach the adapter, which forwards them as Claude image blocks.

const model = anthropic.model({ name: "claude-sonnet-4-6" });

const response = await model.complete([
  {
    role: "user",
    content: [
      { type: "text", text: "What's in this photo?" },
      { type: "image", source: { url: "https://example.com/cat.jpg" } },
    ],
  },
]);

Pricing and usage

Every response reports token usage (input, output, total). Claude bills input and output separately with no pre-summed total, so the adapter computes total itself; prompt-cache reads surface as cachedTokens when present.

To turn tokens into money, attach a pricing registry — keyed by model name, in USD per million tokens. It can live on the SDK (one source of truth) or per-model (wins when both are set). With pricing set, the framework rolls cost up through every node of the AgentReport.

const anthropic = new AnthropicSDK({
  apiKey: process.env.ANTHROPIC_API_KEY!,
  pricing: {
    "claude-haiku-4-5": { input: 1, output: 5, cachedInput: 0.1 },
    "claude-sonnet-4-6": { input: 3, output: 15, cachedInput: 0.3 },
  },
});

Need an offline token estimate before a call? anthropic.count(text) returns a fast character-heuristic approximation — good for budgeting and quota guards, not for billing.

For the agent/workflow surface these models plug into, see @warlock.js/ai. For provider-specific notes and the latest model ids, see the setup-anthropic skill.