HijackClaw

Experimental Project. Use it at your own risk.

Run Claude Code using your ChatGPT/Codex subscription as the backend — no Anthropic API key or Claude session limits required.

We love Claude Code, but sometimes, we can't use it.

• Session limits — You've burned through your Claude Pro/Team allocation, and it's only Tuesday
• No API budget — Anthropic API credits or subscription aren't cheap, and your org won't approve them
• Workplace restrictions — Corporate firewalls or network policies block api.anthropic.com
• Regional availability — Claude API isn't available in your region, but ChatGPT is
• Billing separation — You already pay for ChatGPT Plus/Team and don't want a second AI subscription

HijackClaw solves this by routing Claude Code's API requests through your existing OpenAI Codex subscription session. You get the full Claude Code experience — interactive terminal, agentic workflows, file editing — powered by your ChatGPT account at no extra cost.

1. Sign in with your ChatGPT account (standard OAuth, no passwords stored)
2. HijackClaw spins up a local Anthropic-compatible proxy on 127.0.0.1
3. Claude Code launches in a managed terminal with ANTHROPIC_BASE_URL pointed at the local proxy
4. Requests are translated from Claude's Messages API format to the Codex subscription wire protocol and sent over WebSocket (with SSE fallback)

Your auth tokens are stored locally in ~/.hijackclaw/auth.json and refresh automatically — no browser needed after the initial login.

npm i hijackclaw -g

# Authenticate with your ChatGPT account
hijackclaw login

# Install daemon + shell hook (adds env vars to new shells when proxy is alive)
hijackclaw install
# Run the proxy that reroutes Anthropic calls to OpenAI
hijackclaw serve

# Open a new terminal — Claude Code now routes through OpenAI
claude

Config lives at ~/.hijackclaw/config.json:

{
  "port": 8082,
  "model": "gpt-5.4",
  "smallFastModel": "gpt-5.4-mini",
  "modelMap": {
    "claude-sonnet-4-6": "gpt-5.4",
    "claude-haiku-4-5-20251001": "gpt-5.4-mini",
    "claude-opus": "gpt-5.4"
  }
}

Claude Code (PTY)
    |
    | ANTHROPIC_BASE_URL=http://127.0.0.1:8082
    v
Local Proxy (POST /v1/messages)
    |
    | Translate Claude Messages API -> Codex wire protocol
    v
chatgpt.com/backend-api/codex/responses (WebSocket / SSE)
    |
    | Your ChatGPT subscription session
    v
OpenAI Codex Backend

Key properties:

• Shell hook conditionally exports ANTHROPIC_* env vars only when the proxy is alive (nc -z guard)
• When the proxy is down, Claude Code works normally against Anthropic
• Auth tokens stored locally with automatic refresh
• WebSocket transport with automatic SSE fallback and 30s timeout
• Full tool use support (function calls + results round-trip)

git clone https://github.com/yungookim/hijackclaw.git
cd hijackclaw
npm install
npm run build

npm test             # Run tests
npm run check        # TypeScript type checking

• Unsupported Anthropic features (e.g. image content blocks) fail explicitly rather than degrading silently

HijackClaw is an independent open-source project. It is not affiliated with, endorsed by, or sponsored by Anthropic or OpenAI. Use of this software may be subject to the terms of service of third-party platforms it interacts with. You are solely responsible for ensuring your usage complies with all applicable terms and policies.

This software is provided "as is", without warranty of any kind. See the MIT License for details.

MIT