Copilot API Proxy (Fork)

[!NOTE] This is a fork of ericc-ch/copilot-api with additional improvements and bug fixes.

[!WARNING] This is a reverse proxy for the GitHub Copilot API. It is not officially supported by GitHub and may break at any time. Use at your own risk.

A reverse proxy that exposes GitHub Copilot API as OpenAI and Anthropic compatible API endpoints. Works with Claude Code and other tools that speak OpenAI or Anthropic protocols.

Quick Start

Install from npm (Recommended)

# Run directly
npx -y @hsupu/copilot-api start

Run from Source

git clone https://github.com/puxu-msft/copilot-api-js.git
cd copilot-api-js
bun install
bun run dev      # Development mode with hot reload
bun run start    # Production mode
bun run build    # Build for distribution

Using with Claude Code

Run the interactive setup command:

copilot-api setup-claude-code

Or manually create ~/.claude/settings.json:

{
  "env": {
    "ANTHROPIC_BASE_URL": "http://localhost:4141",
    "ANTHROPIC_AUTH_TOKEN": "dummy",
    "ANTHROPIC_MODEL": "opus",
    "ANTHROPIC_SMALL_FAST_MODEL": "haiku",
    "DISABLE_NON_ESSENTIAL_MODEL_CALLS": "1",
    "CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC": "1"
  }
}

Features

Dual API Compatibility

Exposes both OpenAI and Anthropic compatible endpoints through a single proxy:

• Direct Anthropic path — Uses Copilot API's anthropic endpoint
• Translated path — Translates to OpenAI format and uses Copilot's OpenAI-compatible endpoint

Adaptive Rate Limiting

Intelligent rate limiting with exponential backoff, replacing the upstream queue-based approach. Operates in three modes:

• Normal — Requests pass through freely
• Rate-limited — Queues requests with configurable intervals after hitting limits
• Recovering — Gradually resumes normal operation after consecutive successes

Learns from Copilot API's Retry-After headers for optimal retry timing.

Auto-Truncate

Automatically handles context length limits (enabled by default):

• Reactive — Retries failed requests with a truncated payload when hitting token or byte limits
• Proactive — Pre-checks requests against known model limits before sending
• Dynamic limit learning — Adjusts limits based on actual API error responses
• Tool result compression — Compresses old tool_result content before truncating messages, preserving more conversation context
• Up to 5 retry attempts per request with 2% safety margin

Message Sanitization

Cleans up messages before forwarding to the API:

• Filters orphaned tool_use / tool_result blocks (unpaired due to interrupted tool calls or truncation)
• Handles server-side tools (server_tool_use / *_tool_result) that appear inline in assistant messages
• Fixes double-serialized tool inputs from stream accumulation
• Removes corrupted blocks from older history data
• Fixes tool name casing mismatches
• Removes empty text content blocks
• Strips <system-reminder> tags from message content

Model Name Translation

Translates client-sent model names to matching Copilot models:

| Input | Resolved To | |-------|-------------| | opus, sonnet, haiku | Best available model in that family | | claude-opus-4-6 | claude-opus-4.6 | | claude-sonnet-4-5-20250514 | claude-sonnet-4.5 | | claude-sonnet-4, gpt-4 | Passed through directly |

Each model family has a priority list. Short aliases resolve to the first available model.

Server-Side Tools

Supports Anthropic server-side tools (e.g., web_search, tool_search). These tools are executed by the API backend, with both server_tool_use and result blocks appearing inline in assistant messages. Tool definitions can optionally be rewritten to a custom format (configurable via --no-rewrite-anthropic-tools).

Request History UI

Built-in web interface for inspecting API requests and responses. Access at http://localhost:4141/history.

• Real-time updates via WebSocket
• Filter by model, endpoint, status, and time range
• Full-text search across request/response content
• Export as JSON or CSV
• Session tracking and statistics

Additional Features

• Sonnet → Opus redirection — Optionally redirect sonnet model requests to the best available opus model
• Security research mode — Passphrase-protected mode for authorized penetration testing, CTF competitions, and security education
• Tool name truncation — Automatically truncates tool names exceeding 64 characters (OpenAI limit) with hash suffixes, restoring original names in responses
• Health checks — Container-ready health endpoint at /health
• Graceful shutdown — Connection draining on shutdown signals
• Proxy support — HTTP/HTTPS proxy via environment variables

Commands

| Command | Description | |---------|-------------| | start | Start the API server (authenticates automatically if needed) | | auth | Run GitHub authentication flow only | | logout | Remove stored GitHub token | | check-usage | Show Copilot usage and quota information | | debug info | Display diagnostic information | | debug models | Fetch and display raw model data from Copilot API | | list-claude-code | List all locally installed Claude Code versions | | setup-claude-code | Interactively configure Claude Code to use this proxy |

start Options

| Option | Default | Description | |--------|---------|-------------| | --port, -p | 4141 | Port to listen on | | --host, -H | (all interfaces) | Host/interface to bind to | | --verbose, -v | false | Enable verbose logging | | --account-type, -a | individual | Account type: individual, business, or enterprise | | --manual | false | Manual request approval mode | | --github-token, -g | | Provide GitHub token directly | | --proxy-env | false | Use proxy from environment variables | | --history-limit | 200 | Max history entries in memory (0 = unlimited) |

Rate Limiting:

| Option | Default | Description | |--------|---------|-------------| | --no-rate-limit | false | Disable adaptive rate limiting | | --retry-interval | 10 | Seconds to wait before retrying after rate limit | | --request-interval | 10 | Seconds between requests in rate-limited mode | | --recovery-timeout | 10 | Minutes before attempting recovery | | --consecutive-successes | 5 | Consecutive successes needed to exit rate-limited mode |

Auto-Truncate:

| Option | Default | Description | |--------|---------|-------------| | --no-auto-truncate | false | Disable auto-truncation on context limit errors | | --no-compress-tool-results | false | Disable tool result compression during truncation |

Anthropic-Specific:

| Option | Default | Description | |--------|---------|-------------| | --redirect-anthropic | false | Force Anthropic requests through OpenAI translation | | --no-rewrite-anthropic-tools | false | Don't rewrite server-side tools to custom format | | --redirect-count-tokens | false | Route count_tokens through OpenAI translation | | --redirect-sonnet-to-opus | false | Redirect sonnet requests to best available opus | | --security-research-mode | | Enable security research mode with passphrase |

API Endpoints

OpenAI Compatible

| Endpoint | Method | Description | |----------|--------|-------------| | /v1/chat/completions | POST | Chat completions | | /v1/models | GET | List available models | | /v1/models/:model | GET | Get specific model details | | /v1/embeddings | POST | Text embeddings |

All endpoints also work without the /v1 prefix.

Anthropic Compatible

| Endpoint | Method | Description | |----------|--------|-------------| | /v1/messages | POST | Messages API | | /v1/messages/count_tokens | POST | Token counting | | /api/event_logging/batch | POST | Event logging (no-op, returns OK) |

Utility

| Endpoint | Method | Description | |----------|--------|-------------| | /health | GET | Health check (200 healthy, 503 unhealthy) | | /usage | GET | Copilot usage and quota statistics | | /token | GET | Current Copilot token information | | /history | GET | Request history web UI | | /history/ws | WebSocket | Real-time history updates | | /history/api/entries | GET | Query history entries | | /history/api/stats | GET | Usage statistics | | /history/api/export | GET | Export history (JSON/CSV) | | /history/api/sessions | GET | List sessions |

Account Types

The account type determines the Copilot API base URL:

| Type | API Base URL | |------|-------------| | individual | api.githubcopilot.com | | business | api.business.githubcopilot.com | | enterprise | api.enterprise.githubcopilot.com |

License

MIT