{"version":"2.1.221","anchor":"mcp-authentication-is-refused-for-servers-disabled-elsewhere","canonical_anchor":"mcp-authentication-is-refused-for-servers-disabled-elsewhere","heading":"MCP authentication is refused for servers disabled elsewhere or blocked by policy","tier":"notice","area":"MCP","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.221\/e\/mcp-authentication-is-refused-for-servers-disabled-elsewhere","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.221","markdown":"### MCP authentication is refused for servers disabled elsewhere or blocked by policy\n\nClaude now refuses to start MCP login for servers that are disabled or blocked by policy, and says why.\n\n**What**\n\nThe SDK and control-plane onMcpAuthenticate path now validates the server before starting an OAuth flow, so you get a clear message instead of an authentication that could not have been used.\n\n**Details**\n\n- Checks that MCP UI controls are available, that another session has not disabled the server, and that managed policy does not block it.\n- Each failing check throws user-facing text rather than proceeding.\n- A new managed-policy message was added for the policy-blocked case.\n\n**Evidence**\n\n`MCP server blocked by managed policy; auth refused`\n\n- Area: MCP\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 0\/5"}