LMM for Copilot

Preview: Requires a deployed LMM server with lmm-vscode OAuth registration. The extension checks server support before opening the browser; local tests do not establish production account or model access.

Use the models available to your LMM account in the native VS Code Chat model picker. Sign in with your browser; no API key is required.

Setup

1. Install LMM for Copilot in desktop VS Code 1.104 or newer. Install or enable the VS Code Chat / GitHub Copilot Chat interface if it is not already available.
2. Run LMM: Sign In from the Command Palette. Approve access and select model groups in the LMM browser consent screen.
3. Open Chat, select LMM in the model picker (or Manage Models), and choose a group/model. Run LMM: Refresh Models after changing access.
4. Run LMM: Sign Out to remove the local credential and revoke the server grant.

LMM account balance and current server pricing apply to every request. This extension does not provide free Copilot credits or an inline tab-completion provider. Chat UI availability and account requirements are controlled by your VS Code / Copilot installation.

The consent screen identifies VS Code, and editor credentials remain separate from Pi, Zed, and other LMM clients. An older server without editor registration produces a clear sign-in error rather than opening a misleading authorization page.

OAuth login uses a temporary listener bound only to 127.0.0.1, random state, S256 PKCE, and an issuer-bound callback. Credentials are stored through VS Code SecretStorage. Expiring tokens rotate automatically; a durable hashed journal prevents refresh-token replay across windows or after a crash. If a rotation is interrupted, sign in again. Credentials, authorization codes, prompts, and responses are never logged by this extension.

The extension runs on the desktop UI host, including Remote SSH workspaces. Browser-only vscode.dev is not supported. A browser must be able to reach the VS Code computer's loopback address. No issuer override or API-key fallback is supported.

Models and tools

The OAuth catalog determines available groups and models. This version supports catalog entries advertising the OpenAI chat completions API, streams text and function-call deltas, and passes text tool results back to the model. Responses-only and Anthropic-only catalog entries are excluded. Images and non-text tool results are unsupported and produce a clear error.

The catalog does not provide verified context limits or function-calling capability. The default settings advertise a conservative 32,768 input / 4,096 output token budget, rather than a claim about a model's full context. Set lmm.maxInputTokens and lmm.maxOutputTokens at or below the supported limits of all models you use. Token counting is a conservative UTF-8 byte estimate, not the model's exact tokenizer.

Tools are disabled by default. After verifying that a model supports OpenAI function calling, add its exact upstream model ID to lmm.toolModels. Refresh the picker; the model can then be selected for tool-based Chat/Agent workflows. The provider emits tool calls to VS Code; VS Code owns approvals and tool execution. No arbitrary model option can override the OAuth group, relay destination, or credentials. Billable requests are never retried automatically.

Build and test

npm ci --ignore-scripts
npm test
npm run package
# Optional real desktop extension-host smoke (installed VS Code and a display required):
npm run test:host

npm test compiles against the stable VS Code 1.104 API and runs OAuth rotation, cross-window replay, catalog authorization, callback security, and SSE tests. npm run package creates lmm-copilot-provider-0.1.1.vsix; the extension has no runtime npm dependencies.

Install the local package with code --install-extension ./lmm-copilot-provider-0.1.1.vsix. A real OAuth/model request requires the production server to register public native client lmm-vscode with loopback /oauth/lmm/callback, the required scopes, and the OAuth relay endpoints.

Marketplace publishing

The manifest publisher is LIghtJUNction. Publishing requires control of that exact Visual Studio Marketplace publisher and an Azure DevOps Personal Access Token authorized to manage extensions. Run npx vsce publish --packagePath ./lmm-copilot-provider-0.1.1.vsix from an authenticated publisher environment. Open VSX additionally requires an Open VSX account, a matching owned namespace, publisher agreement, and its own access token. Never put publishing tokens in repository files.

Packaging and automated tests do not establish a successful browser OAuth session, paid model request, or Marketplace listing. Those must be verified separately.

Development sources

The provider follows Microsoft's Language Model Chat Provider API, stable 1.104 API types, and official provider sample. OAuth relay contracts are implemented by the LMM server in this repository.