Before using the Microsoft C++ Language Server, you must accept the end-user license agreement (EULA), which is distributed as EULA/LICENSE.txt in the npm package. Accept the agreement by running npx @microsoft/cpp-language-server --accept-eula (or mscppls --accept-eula if installed directly). You only need to accept the EULA once.
Using the Microsoft C++ Language Server requires an active GitHub Copilot subscription. Before using the language server for the first time, log in to GitHub by running npx @microsoft/cpp-language-server --login (or mscppls --login if installed directly) and following the on-screen instructions.
By default, the language server stores your GitHub tokens in system secret storage. On Linux, this requires libsecret. If you are running the language server in a constrained environment where system secret storage is unavailable, run npx @microsoft/cpp-language-server --login --allow-plaintext-secret-storage (or mscppls --login --allow-plaintext-secret-storage if installed directly) to allow storing the tokens in plaintext.
Alternatively, you can independently generate a GitHub token (such as a PAT) and save it in the MSCPPLS_GITHUB_TOKEN environment variable. The token does not need to have any scopes.
If no token is found in system secret storage or the MSCPPLS_GITHUB_TOKEN environment variable, the language server will fall back to the GitHub CLI and run gh auth token to obtain a token for the current session. This requires the GitHub CLI (gh) to already be installed and on your PATH, and that you have authenticated with it (for example, via gh auth login). The token is used only for the current session and is not stored by the language server.
This is the recommended way to use the language server with GitHub Enterprise Cloud. Authenticate the GitHub CLI against your enterprise host and then point the language server at the same host with --login-hostname:
gh auth login --hostname myenterprise.ghe.com
mscppls --login-hostname myenterprise.ghe.com
The --login-hostname value is passed through to gh auth token --hostname <host>. If omitted, the GitHub CLI's default host (github.com) is used. Classic personal access tokens (those beginning with ghp_) returned by the GitHub CLI are rejected.
--login-hostname can be added to the args in lsp.json to pass it every time the language server launches. See customizing Copilot CLI launch flags.