@0xkinance/x402-anthropic

x402-anthropic-typescript

x402 payment transport for the Anthropic TypeScript SDK.

Wrap the standard Anthropic client with a crypto wallet. When the server responds with HTTP 402, the library automatically signs a USDC payment and retries — zero code changes needed. Follows the pattern introduced by qntx/x402-openai-typescript.

Install

npm install @0xkinance/x402-anthropic @x402/evm viem        # EVM (Base, Ethereum)
npm install @0xkinance/x402-anthropic @x402/svm @solana/kit  # SVM (Solana)
npm install @0xkinance/x402-anthropic @x402/evm @x402/svm viem @solana/kit  # all chains

Quick start

import { X402Anthropic, EVMWallet } from "@0xkinance/x402-anthropic";

const client = new X402Anthropic({
  wallet: new EVMWallet("0x..."),
  baseURL: "https://your-x402-gateway.example.com",
});

const message = await client.messages.create({
  model: "claude-opus-4-5",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Hello!" }],
});
console.log(message.content[0]);

Swap EVMWallet for SVMWallet to pay on Solana — the API is identical.

Usage

Streaming

const stream = await client.messages.stream({
  model: "claude-opus-4-5",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Tell me a story." }],
});
for await (const text of stream.textStream) {
  process.stdout.write(text);
}

Payment policies

import { X402Anthropic, EVMWallet, preferNetwork, maxAmount } from "@0xkinance/x402-anthropic";

const client = new X402Anthropic({
  wallet: new EVMWallet("0x..."),
  policies: [preferNetwork("eip155:8453"), maxAmount(1_000_000n)],  // Base, max $1 USDC
  baseURL: "...",
});

API reference

X402Anthropic

Drop-in replacement for Anthropic from @anthropic-ai/sdk.

All standard Anthropic options (timeout, maxRetries, apiKey, …) are forwarded.

Wallet adapters

Implement the Wallet interface to add a new chain.

Policy helpers

Examples

EVM_PRIVATE_KEY="0x..."        npx tsx examples/basic.ts
EVM_PRIVATE_KEY="0x..."        npx tsx examples/streaming.ts

Related

• x402-anthropic-python — Python version of this library
• qntx/x402-openai-typescript — OpenAI SDK equivalent
• coinbase/x402 — x402 protocol spec and reference implementation

License

MIT