fix(mcp): strip trailing slash from OAuth resource parameter#14001
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venkat22022202 wants to merge 2 commits intovercel:mainfrom
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fix(mcp): strip trailing slash from OAuth resource parameter#14001venkat22022202 wants to merge 2 commits intovercel:mainfrom
venkat22022202 wants to merge 2 commits intovercel:mainfrom
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`new URL("https://mcp.example.com").href` returns
"https://mcp.example.com/" per the URL spec. Auth servers that do
exact matching on the resource parameter reject the request because
the trailing slash makes it a different URI than what was registered.
The MCP spec recommends the form without trailing slash:
https://modelcontextprotocol.io/specification/2025-11-25/basic/authorization#canonical-server-uri
Fix: strip trailing slash from `resource.href` in all three locations
where it's used as an OAuth parameter (startAuthorization,
exchangeAuthorization, refreshAuthorization).
Fixes vercel#13988
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Address review feedback: the blanket regex would strip trailing slashes from path-based resource URIs like https://host/api/ which may be intentional. Extract canonicalResourceUri() helper that only strips the trailing slash when pathname is exactly "/" (origin-only URL). Path-based resource URIs are left unchanged.
Author
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Good catch — fixed in 8206bfa. Extracted a |
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Summary
Fixes #13988
new URL("https://mcp.example.com").hrefreturns"https://mcp.example.com/"per the URL spec. Auth servers that do exact matching on theresourceparameter reject the request because the trailing slash makes it a different URI than what was registered.Fix
Strip trailing slash from
resource.hrefin all three locations where it's used as an OAuth parameter:startAuthorization(line 454)exchangeAuthorization(line 678)refreshAuthorization(line 765)Why this is correct
The MCP spec explicitly recommends the form without trailing slash for better interoperability:
Source: https://modelcontextprotocol.io/specification/2025-11-25/basic/authorization#canonical-server-uri
Test plan
https://mcp.example.com) should no longer get rejected by auth servers doing exact matchhttps://mcp.example.com/api) are unaffected (no trailing slash to strip)