MCP access tokens are now fully isolated from general REST APIs, so a limited token such as keys:read can't reach administrative endpoints.

Other hardening in this release:

Client registration: Dynamic Client Registration (RFC 7591) now validates redirect URIs and their length. It allows https:, loopback http:, and verified native app schemes, and rejects javascript:, data:, and fragment identifiers.
PKCE: S256 verification now uses constant-time comparison.
Headers: OAuth token endpoints send Cache-Control: no-store and Pragma: no-cache, and /mcp, /oauth/token, /oauth/register, and metadata endpoints handle CORS preflight requests.