Fix resource metadata discovery URL construction to comply with MCP spec for subpath deployments#1110
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AnkeshThakur wants to merge 1 commit intomodelcontextprotocol:mainfrom
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Fix resource metadata discovery URL construction to comply with MCP spec for subpath deployments#1110AnkeshThakur wants to merge 1 commit intomodelcontextprotocol:mainfrom
AnkeshThakur wants to merge 1 commit intomodelcontextprotocol:mainfrom
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…pec for subpath deployments Per RFC 9728 §3 and the MCP spec (https://modelcontextprotocol.io/specification/2025-11-25/basic/authorization#protected-resource-metadata-discovery-requirements), the .well-known/oauth-protected-resource URL is formed by inserting the well-known prefix at the origin root and appending the resource path after it: https://example.com/public/mcp → https://example.com/.well-known/oauth-protected-resource/public/mcp The previous code used `new URL("/.well-known/oauth-protected-resource", serverUrl)` which always resolves to the host root, ignoring the resource path entirely. This broke metadata discovery for any subpath-deployed MCP server (issue modelcontextprotocol#1008). Changes: - Add `getResourceMetadataDiscoveryUrl()` in oauthUtils.ts that prepends /.well-known/oauth-protected-resource at the origin and appends the resource pathname (trailing slash stripped), matching the MCP SDK implementation - Replace all three inline well-known URL constructions in OAuthFlowProgress.tsx with the new utility via a memoized `resourceMetadataDiscoveryUrl` variable - Add 6 unit tests covering: single-segment path, subpath, deep path, trailing slash, no path, and URL object input Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
getResourceMetadataDiscoveryUrl()utility inoauthUtils.tsthat correctly constructs the protected resource metadata discovery URL per RFC 9728 §3 and the MCP specnew URL("/.well-known/oauth-protected-resource", serverUrl)usages inOAuthFlowProgress.tsxwith the new utility via a memoizedresourceMetadataDiscoveryUrlvariableProblem
The previous code used:
This always resolves to the host root, ignoring the resource endpoint path entirely. For subpath-deployed MCP servers (e.g.
https://host/public/mcp), the metadata URL was incorrectly constructed ashttps://host/.well-known/oauth-protected-resourceinstead ofhttps://host/.well-known/oauth-protected-resource/public/mcp.Fixes #1008.
Spec Compliance
Per RFC 9728 §3 and the MCP spec §authorization#protected-resource-metadata-discovery-requirements, the well-known URL is formed by inserting
/.well-known/oauth-protected-resourceat the origin root and appending the full resource path after it:https://host/public/mcphttps://host/.well-known/oauth-protected-resource/public/mcphttps://host/resourcehttps://host/.well-known/oauth-protected-resource/resourcehttps://host(no path)https://host/.well-known/oauth-protected-resourceThis matches the MCP SDK's own implementation:
new URL(`/.well-known/oauth-protected-resource${rsPath}`, u).Test plan
npm testinclient/)🤖 Generated with Claude Code