claude-api-proxy

Anthropic API key rotation proxy for Claude Code — seamlessly switch keys when one account's quota runs out.

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claude-api-proxy setup      # add your API keys
claude-api-proxy            # start proxy + launch Claude Code
claude-api-proxy status     # see which key is active

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How it works

claude-api-proxy runs a local HTTP proxy on port 3131. It starts Claude Code as a child process with ANTHROPIC_BASE_URL pointing at the proxy. Every API request is forwarded to api.anthropic.com with the currently active key injected.

When a quota or credit exhaustion error is detected (402, 429, 529 / credit_balance_too_low, rate_limit_error, overloaded_error), the proxy silently rotates to the next configured key and retries — without interrupting your Claude Code session.

[claude-api-proxy] ⚡ KEY ROTATED: work → personal

If all keys are exhausted, the original error is passed back to Claude Code unchanged.

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Requirements

• Node.js 18+
• Claude Code installed and in your PATH

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Install

npm install -g claude-api-proxy

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Quick start

1. Add your API keys:

claude-api-proxy setup

[claude-api-proxy] Setup — Add your Anthropic API keys
Keys are stored in ~/.claude-api-proxy.json

Key label (e.g. "work", "personal") [leave blank to finish]: work
API key for "work" (sk-ant-...): sk-ant-api03-...
  ✓  Added key "work"

Add another key? (y/N): y
Key label (e.g. "work", "personal") [leave blank to finish]: personal
API key for "personal" (sk-ant-...): sk-ant-api03-...
  ✓  Added key "personal"

Add another key? (y/N): n

✓ Saved 2 key(s) to ~/.claude-api-proxy.json

2. Start the proxy and Claude Code:

claude-api-proxy

That's it. Claude Code launches automatically with the proxy configured. When the first key hits its quota, the proxy rotates to the next key transparently.

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Commands

claude-api-proxy setup

Interactive wizard to add API keys. Stores them in ~/.claude-api-proxy.json.

claude-api-proxy status

List all configured keys with their labels and which one is currently active.

[claude-api-proxy] Configured API keys:

  [1] work                 sk-ant-api03...xxxx ← active
  [2] personal             sk-ant-api03...yyyy

claude-api-proxy

Start the proxy on port 3131 and launch claude with the correct environment variables injected (ANTHROPIC_BASE_URL, ANTHROPIC_API_KEY).

claude-api-proxy --no-launch

Start the proxy only. Useful if you want to launch Claude Code manually or connect another tool.

claude-api-proxy --no-launch
# Proxy running. Launch claude manually:
#   ANTHROPIC_BASE_URL=http://127.0.0.1:3131 ANTHROPIC_API_KEY=proxy claude

claude-api-proxy --port <n>

Use a custom port instead of the default 3131.

claude-api-proxy --port 8080

claude-api-proxy --verbose / -v

Log each forwarded request and which key is being used to stderr.

[claude-api-proxy] → POST /v1/messages (key: work)

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Key storage

Keys are stored in ~/.claude-api-proxy.json:

{
  "keys": [
    { "label": "work",     "key": "sk-ant-...", "active": true },
    { "label": "personal", "key": "sk-ant-...", "active": true }
  ],
  "currentIndex": 0
}

The proxy rotates currentIndex forward on exhaustion. After cycling through all keys, it resets. The file is updated on disk after each rotation so the active key persists across restarts.

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Platform support

Platform	Status
Linux	✅ Supported
macOS	✅ Supported
Windows	✅ Supported

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Contributing

See CONTRIBUTING.md for local dev setup, architecture notes, and the release process.

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License

MIT — see LICENSE.