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's API as standard OpenAI and Anthropic compatible endpoints. Works with Claude Code, Cursor, and other tools that speak these protocols.

Quick Start

Install from npm (Recommended)

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

# Testing
bun test                   # Backend unit tests
bun run test:all           # All backend tests
bun run test:ui            # Frontend (History UI) tests
bun run typecheck          # TypeScript type checking

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 native Anthropic endpoint for Claude models
• OpenAI-compatible path — Forwards OpenAI Chat Completions, Responses, Embeddings, and Models requests to Copilot's OpenAI endpoints

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

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)
• Fixes tool name casing mismatches
• Removes empty text content blocks
• Strips <system-reminder> tags from message content
• [Optional] Deduplicates repeated tool calls (config.yaml: anthropic.dedup_tool_calls)
• [Optional] Strips system-reminder tags from Read tool results (config.yaml: anthropic.truncate_read_tool_result)

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-4-6-20250514 | claude-sonnet-4.6 | | claude-opus-4-6-fast, opus[1m] | claude-opus-4.6-fast, claude-opus-4.6-1m | | claude-sonnet-4, gpt-4 | Passed through directly |

User-configured model_overrides (via config.yaml) can redirect any model name to another, with chained resolution and family-level overrides.

Server-Side Tools

Supports Anthropic server-side tools (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 (--no-rewrite-anthropic-tools).

Request History UI

Built-in web interface for inspecting API requests and responses. Access at http://localhost:4141/history/v3/.

• Real-time updates via WebSocket
• Filter by model, endpoint, status, and time range
• Session tracking and statistics

Additional Features

• Model overrides — Configure arbitrary model name redirections via config.yaml
• Adaptive rate limiting — Intelligent rate limiting with exponential backoff (3 modes: Normal, Rate-limited, Recovering)
• Tool name truncation — Truncates tool names exceeding 64 characters (OpenAI limit) with hash suffixes
• Health checks — Container-ready 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

General:

| 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 | | --github-token, -g | | Provide GitHub token directly | | --no-http-proxy-from-env | enabled | Disable HTTP proxy from environment variables |

Auto-Truncate:

| Option | Default | Description | |--------|---------|-------------| | --no-auto-truncate | enabled | Disable auto-truncation on context limit errors |

Anthropic-Specific (via config.yaml):

These options are configured in config.yaml under the anthropic: section. See config.example.yaml.

| Config Key | Default | Description | |------------|---------|-------------| | anthropic.rewrite_tools | true | Rewrite server-side tools to custom format | | stream_idle_timeout | 300 | Max seconds between SSE events (0 = no timeout) |

Sanitization:

| Option | Default | Description | |--------|---------|-------------| | --collect-system-prompts | false | Collect system prompts to file |

Rate Limiting:

| Option | Default | Description | |--------|---------|-------------| | --no-rate-limit | enabled | Disable adaptive rate limiting |

Rate limiter sub-parameters are configured in config.yaml under rate_limiter:. See config.example.yaml.

Configuration

Create a config.yaml in the working directory. See config.example.yaml for all available options.

API Endpoints

OpenAI Compatible

| Endpoint | Method | Description | |----------|--------|-------------| | /v1/chat/completions | POST | Chat completions | | /v1/responses | POST | Responses API | | /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 |

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/v3/ | GET | History web UI | | /history/ws | WebSocket | Real-time history updates | | /history/api/entries | GET | Query history entries | | /history/api/entries/:id | GET | Get single entry | | /history/api/summaries | GET | Entry summaries | | /history/api/stats | GET | Usage statistics | | /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