claude-oauth

Use your Claude Max or Claude Pro subscription via OAuth to access the Claude API - no API keys needed!

Installation

npm install @tfw.in/claude-oauth

Quick Start

# Login (one-time)
npx @tfw.in/claude-oauth --login

# Chat directly
npx @tfw.in/claude-oauth "What is the meaning of life?"

Usage

Standalone CLI

# Simple prompt
npx @tfw.in/claude-oauth "Explain quantum computing in one sentence"

# Login/re-authenticate
npx @tfw.in/claude-oauth --login

# Help
npx @tfw.in/claude-oauth --help

OpenAI SDK

import OpenAI from 'openai';
import { createOAuthFetch } from '@tfw.in/claude-oauth';

const client = new OpenAI({
  baseURL: 'https://api.anthropic.com/v1/',
  apiKey: 'oauth', // Placeholder
  fetch: createOAuthFetch(),
});

const response = await client.chat.completions.create({
  model: 'claude-sonnet-4-20250514',
  max_tokens: 100,
  messages: [{ role: 'user', content: 'Hello!' }],
});

console.log(response.choices[0].message.content);

Anthropic SDK

import Anthropic from '@anthropic-ai/sdk';
import { createOAuthFetch } from '@tfw.in/claude-oauth';

const client = new Anthropic({
  apiKey: 'oauth-placeholder',
  fetch: createOAuthFetch(),
});

const response = await client.messages.create({
  model: 'claude-sonnet-4-20250514',
  max_tokens: 100,
  messages: [{ role: 'user', content: 'Hello!' }],
});

console.log(response.content[0].text);

Programmatic Usage

import { chat, login } from '@tfw.in/claude-oauth';

// Login programmatically
await login();

// Simple chat
const response = await chat("What is 2+2?");
console.log(response.content[0].text);

// With options
const response = await chat("Hello", {
  model: 'claude-sonnet-4-20250514',
  maxTokens: 1000,
  system: 'You are a helpful assistant',
});

How It Works

This package uses Anthropic's OAuth flow (the same one Claude Code uses) to authenticate your Claude Max/Pro subscription. Key requirements handled automatically:

1. Required Beta Headers - OAuth-specific headers are injected
2. System Prompt Validation - OAuth tokens require a specific system prompt prefix

Token Storage

Tokens are stored at ~/.claude-oauth/auth.json by default.

Override with environment variable:

export CLAUDE_AUTH_FILE=/custom/path/auth.json

Or use direct tokens:

export ACCESS_TOKEN=sk-ant-oat01-...
export REFRESH_TOKEN=...

API

createOAuthFetch(originalFetch?)

Creates a fetch function that handles OAuth authentication. Use this to patch any SDK.

chat(prompt, options?)

Simple chat function. Options: model, maxTokens, system.

login()

Interactive OAuth login flow.

CONFIG

Configuration object with OAuth endpoints and settings.

License

MIT