@frontmcp/auth

Authentication and authorization for FrontMCP servers: the five auth modes, OAuth 2.1 sign-in with FrontMCP as its own authorization server or in front of your identity provider, JSON Web Token (JWT) and session checks, access rules on tools, and the built-in sign-in pages. @frontmcp/sdk depends on this package, so a FrontMCP server already has it, and you configure it through @FrontMcp({ auth }). Install it yourself only to import something the SDK doesn't re-export, like escapeHtml for a custom sign-in page or AuthorityDeniedError.

Install

A FrontMCP server doesn't need this step: @frontmcp/sdk installs @frontmcp/auth. To import from it directly:

npm install @frontmcp/auth

Use the same version as @frontmcp/sdk. It needs Node.js 24 or later.

Usage

Set auth on @FrontMcp; its schema comes from this package. Here users sign in at your identity provider, and FrontMCP issues the tokens MCP clients send:

import { FrontMcp } from '@frontmcp/sdk';

import { DeskApp } from './desk.app';

@FrontMcp({
  info: { name: 'desk', version: '1.0.0' },
  apps: [DeskApp],
  auth: {
    mode: 'remote',
    provider: 'https://idp.example.com',
    clientId: 'desk-mcp',
    clientSecret: process.env.IDP_CLIENT_SECRET,
    scopes: ['openid', 'profile', 'email'],
  },
})
export default class Server {}

In production, set JWT_SECRET: FrontMCP signs its tokens with it. Remote and proxied auth lists every option, and the callback URL to register at your provider. mode is one of:

Importing from the package directly

In local mode, login.render replaces the sign-in page. FrontMCP doesn't escape what you print, so pass every value through escapeHtml:

import { escapeHtml } from '@frontmcp/auth';
import { FrontMcp } from '@frontmcp/sdk';

import { DeskApp } from './desk.app';

@FrontMcp({
  info: { name: 'desk', version: '1.0.0' },
  apps: [DeskApp],
  auth: {
    mode: 'local',
    login: {
      fields: { deskKey: { type: 'password', label: 'Desk key', required: true } },
      render: (ctx) => `<!doctype html>
<html lang="en">
  <body>
    <p>${escapeHtml(ctx.clientName)} wants to connect to your desk.</p>
    ${ctx.error ? `<p role="alert">${escapeHtml(ctx.error)}</p>` : ''}
    <form method="POST" action="${escapeHtml(ctx.callbackPath)}">
      <input type="hidden" name="pending_auth_id" value="${escapeHtml(ctx.pendingAuthId)}">
      <label>Desk key <input type="password" name="deskKey" required></label>
      <button>Sign in</button>
    </form>
  </body>
</html>`,
    },
    authenticate: async ({ fields }) =>
      fields.deskKey === process.env.DESK_KEY
        ? { ok: true, sub: 'operator' }
        : { ok: false, message: 'Unknown desk key' },
  },
})
export default class Server {}

What's in it

• Auth modes: authOptionsSchema and the option types of each mode. See Auth modes.
• Local mode: FrontMCP as an OAuth 2.1 authorization server, with PKCE (Proof Key for Code Exchange), dynamic client registration and refresh tokens. See Local auth.
• Remote mode: users sign in at your identity provider, and FrontMCP issues the tokens. See Remote and proxied auth.
• Upstream providers: several OAuth providers linked in one sign-in, on one picker page or one provider per page (incrementalAuth.showAllAppsAtOnce: false, buildFederatedStepPage). See Upstream providers.
• Token checks: JWT verification against a JSON Web Key Set (JWKS), and audience and scope checks (JwksService, validateAudience). See Tokens and sessions.
• CIMD (Client ID Metadata Documents): clients whose client_id is the URL of a metadata document (CimdService). A public client declares token_endpoint_auth_method: 'none'; a confidential one declares private_key_jwt and authenticates at the token endpoint with a client assertion signed by a key from its jwks / jwks_uri (RFC 7523, CimdService.verifyClientAssertion). See Client ID metadata.
• Authorities: rules on tools, resources, prompts, skills and agents, from roles, permissions, token claims, the call's arguments or your own code (AuthorityDeniedError). See Authorities.
• Credential vault: per-user credentials that tools read with this.credentials, and that users can add to mid-session. See Progressive auth.
• Sign-in pages: the built-in sign-in, consent and error pages, and escapeHtml, buildLoginPage and baseLayout for your own. See Custom login UI.
• Storage: memory, Redis, Vercel KV and SQLite stores for sessions, authorization codes and tokens, and encrypted storage for secrets (EncryptedTypedStorage, TokenVault). See Local auth storage.

Docs

• Authentication and authorization: an overview, and which page covers which task
• Auth in production: secrets, HTTPS, token checks and several instances
• this.auth: who is calling, from inside a tool
• Authenticating clients and Authorizing calls: step-by-step guides
• Testing authentication

Related packages

• @frontmcp/sdk: the framework. It runs this package and re-exports its option types.
• @frontmcp/utils: the crypto (PKCE, encryption, key derivation) and storage adapters this package builds on.
• @frontmcp/ui: @frontmcp/ui/auth, for React sign-in pages set with auth.ui.
• @frontmcp/testing: token factories and mock OAuth servers for tests.

Contributing

Source: libs/auth. Issues and pull requests are welcome; see CONTRIBUTING.md.

License

Apache-2.0. See LICENSE.