fix: remove Content-Type header from OAuth metadata discovery GET requests#1157
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MumuTW wants to merge 1 commit intomodelcontextprotocol:mainfrom
Open
fix: remove Content-Type header from OAuth metadata discovery GET requests#1157MumuTW wants to merge 1 commit intomodelcontextprotocol:mainfrom
MumuTW wants to merge 1 commit intomodelcontextprotocol:mainfrom
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…iscovery GET requests to /.well-known/oauth-authorization-server should not include a Content-Type header. Some authorization servers (e.g. Keycloak) respond with 415 Unsupported Media Type when a GET request carries Content-Type: application/json, breaking OAuth metadata discovery. Move Content-Type assignment inside the custom fetch wrapper so it is only applied when the request carries a body (i.e. POST), leaving GET requests header-clean. Fixes modelcontextprotocol#1143
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Summary
Fixes #1143
The custom
fetchwrappers in both the SSE and Streamable HTTP direct-connection paths unconditionally setContent-Type: application/jsonon every outgoing request. This includes GET requests made during OAuth metadata discovery (e.g.GET /.well-known/oauth-authorization-server), which violates HTTP semantics — GET requests should not carry aContent-Typeheader.Some authorization servers (notably Keycloak) enforce this and respond with 415 Unsupported Media Type, breaking the entire OAuth flow.
Changes
content-type: application/jsonfrom the sharedrequestHeadersobject into thefetchwrapper, only applying it when the request has a body (init?.body).Content-Typeis now set conditionally inside thefetchwrapper rather than unconditionally before every request.Both changes use a shallow copy (
mergedHeaders) so the baserequestHeadersobject is not mutated across calls.Test plan
GET /.well-known/oauth-authorization-server) no longer returns 415Content-Type: application/json