omp-github-copilot-legacy

An omp extension that registers a github-copilot-legacy provider. It talks to GitHub Copilot through the classic editor REST flow — OAuth device flow plus copilot_internal/v2/token exchange — with no Copilot CLI / SDK involved.

How it differs from the built-in github-copilot provider

| | built-in github-copilot | github-copilot-legacy (this extension) | | ------------------- | -------------------------------------- | --------------------------------------------- | | OAuth app | Copilot CLI app (Ov23ct…) | Legacy editor app (Iv1.b507a08c87ecfe98) | | API credential | GitHub OAuth token used directly | Short-lived Copilot token from GET api.github.com/copilot_internal/v2/token, auto-refreshed | | Token lifetime | ~10 years (far-future expiry) | ~30 min (expires_at/refresh_in), minus 2 min safety margin | | Request identity | Copilot-Integration-Id: copilot-developer-cli, Copilot-Harness-Id: copilot-sdk | Copilot-Integration-Id: vscode-chat, GitHubCopilotChat UA, no SDK headers | | Transport | Per-model routes (completions / responses / Anthropic) | openai-completions (<api>/chat/completions) for every model | | Model catalog | Bundled + live discovery | 3 static fallbacks + live /models discovery |

Install

Use it once:

omp -e /path/to/omp-github-copilot-legacy/src/index.ts

Or link it persistently as a plugin:

omp plugin link /path/to/omp-github-copilot-legacy

Login

In omp, run /login and pick GitHub Copilot (Legacy REST). A device code is shown; approve it at https://github.com/login/device. Login exchanges the GitHub token for a short-lived Copilot token and stores:

• refresh: long-lived GitHub OAuth token (ghu_/gho_)
• access: short-lived Copilot bearer (drives omp auto-refresh via expires)
• apiEndpoint: plan-specific host (api.githubcopilot.com or api.business.githubcopilot.com, drives per-request routing)

Then select a model, e.g.:

omp --model github-copilot-legacy/gpt-4o

Environment

• GITHUB_COPILOT_LEGACY_CLIENT_ID — override the legacy OAuth app id (default Iv1.b507a08c87ecfe98).
• GITHUB_COPILOT_LEGACY_BASE_URL — redirect the transport (forward proxy or local test server). Normal use never sets this.

Limitations

• Personal github.com OAuth only; no Enterprise-host prompt in v1 (business-plan accounts still work — the token exchange advertises the api.business.githubcopilot.com endpoint automatically).
• No thinking-effort dial: models register with reasoning: false, so the effort selector is hidden. Models themselves work normally.
• Usage is billed against your Copilot subscription; recorded cost is 0.

Development

bun install
bun test        # 24 unit tests, mocked fetch, no network
bunx tsc --noEmit

src/copilot-legacy.ts holds all protocol logic behind an injectable fetch; src/index.ts is the thin pi.registerProvider wiring. End-to-end wire verification is done against a local capture server (GITHUB_COPILOT_LEGACY_BASE_URL=http://127.0.0.1:PORT + --api-key), asserting the request line, Bearer auth, legacy headers, and SSE parsing.