{"version":"2.1.275","anchor":"new-mcp-connection-failure-diagnostics-error-code-enum-surf","canonical_anchor":"new-mcp-connection-failure-diagnostics-error-code-enum-surf","heading":"New MCP connection failure diagnostics: error_code enum surfaced to hosts","tier":"notice","area":"MCP","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.275\/e\/new-mcp-connection-failure-diagnostics-error-code-enum-surf","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.275","markdown":"### New MCP connection failure diagnostics: error_code enum surfaced to hosts\n\nMCP server connection failures now report a specific error code explaining why\n\n**What**\n\nWhen a connection to an MCP server (Model Context Protocol, used to connect Claude Code to external tools and data) fails, the status output now includes an `error_code` field giving a specific reason, such as a rejected claude.ai login token, a rejected first-party Anthropic credential, or a connection that's pending approval.\n\n**Why**\n\nThis makes it clear why an MCP connection is failing, such as needing to sign in again, instead of just showing a generic failure with no explanation.\n\n- Area: MCP\n- Names: `error_code`\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 2\/5"}