@galin.iliev/codex-proxy

A local proxy that lets OpenAI Codex CLI and Claude Code use GitHub Copilot as their model backend.

How it works

Codex CLI   ── OpenAI Responses API ─┐
                                     ├─> localhost:8080 ─> GitHub Copilot
Claude Code ── Anthropic Messages API ┘

The proxy:

1. Forwards OpenAI Responses and Chat Completions requests with Copilot authentication headers.
2. Translates Claude Code's POST /v1/messages requests into Copilot Chat Completions requests.
3. Translates normal and streaming Copilot responses back into Anthropic Messages API JSON and SSE events, including text, images, and tool use.
4. Binds to 127.0.0.1 and accepts browser CORS requests only from localhost.

Prerequisites

• Node.js >= 18
• GitHub Copilot subscription (individual, business, or enterprise)

Quick start

npm install
npm start

On first run, the proxy prompts for GitHub device-code authentication if no usable saved, CLI, or explicit token is available.

Codex CLI

OPENAI_BASE_URL=http://localhost:8080/v1 OPENAI_API_KEY=dummy codex

Claude Code

ANTHROPIC_BASE_URL=http://localhost:8080 \
ANTHROPIC_AUTH_TOKEN=dummy \
ANTHROPIC_MODEL=claude-sonnet-4 \
claude

PowerShell:

$env:ANTHROPIC_BASE_URL = "http://localhost:8080"
$env:ANTHROPIC_AUTH_TOKEN = "dummy"
$env:ANTHROPIC_MODEL = "claude-sonnet-4"
claude

Scripts/startClaude.ps1 applies the Claude Code environment variables after you start the proxy in another terminal.

Install from npm

npm install -g @galin.iliev/codex-proxy
codex-copilot-proxy

Options

-p, --port <port>           Port to listen on (default: 8080)
-a, --account-type <type>   individual | business | enterprise (default: individual)
-g, --github-token <token>  GitHub token (or set GH_TOKEN)
    --skip-token-exchange   Use only behind a trusted egress proxy that rewrites Authorization
-h, --help                  Show help

Using with gh CLI token

If you're already authenticated with the GitHub CLI:

node src/index.js --github-token "$(gh auth token)"

Supported endpoints

| Local endpoint | Behavior | |---|---| | POST /v1/responses | Passes through to Copilot /v1/responses | | POST /v1/chat/completions | Passes through to Copilot /chat/completions | | POST /v1/messages | Translates Anthropic Messages to/from Copilot Chat Completions | | GET /v1/models | Passes through to Copilot /models | | GET / | Health check |

The Claude interface follows the behavior of [email protected], with translation kept inside this proxy so Codex and Claude Code share one authentication and server process.