fix: include scope parameter in OAuth authorization code token exchange#1669
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Vadaski wants to merge 1 commit intomodelcontextprotocol:mainfrom
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fix: include scope parameter in OAuth authorization code token exchange#1669Vadaski wants to merge 1 commit intomodelcontextprotocol:mainfrom
Vadaski wants to merge 1 commit intomodelcontextprotocol:mainfrom
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…ontextprotocol#941) - `prepareAuthorizationCodeRequest()` now accepts an optional `scope` parameter and appends it to the token request body when provided, keeping the call backwards compatible. - `fetchToken()` gains a `scope` option. For the `authorization_code` path it forwards *only* the explicitly supplied scope so that a server which narrowed the granted scope during authorization does not receive a broader re-assertion (RFC 6749 §4.1.3). For the custom `prepareTokenRequest()` path (client_credentials, jwt-bearer, …) it retains the previous behaviour of falling back to `provider.clientMetadata.scope`, because those flows initiate a fresh token request rather than redeeming a pre-authorized grant. - `auth()` computes `tokenExchangeScope` as the explicit scope from the WWW-Authenticate challenge only; it does not inject PRM scopes or clientMetadata.scope into the token exchange, preventing invalid_scope errors from providers (e.g. Azure AD) that narrow the granted scope at the authorization endpoint. Closes modelcontextprotocol#941 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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@modelcontextprotocol/express
@modelcontextprotocol/hono
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Problem
When exchanging an authorization code for tokens, the SDK never included a
scopeparameter in the token request. This breaks providers (e.g. Azure AD) that require the scope to be re-stated in the token exchange, and prevents callers from controlling which scope is requested.Closes #941
Root Cause
prepareAuthorizationCodeRequest()had noscopeparameter; andfetchToken()/auth()had no way to thread scope through to the token endpoint.Changes
prepareAuthorizationCodeRequest()Added an optional
scope?: stringparameter. When provided it is appended to theURLSearchParams; when omitted the function behaves exactly as before (no scope field, fully backwards compatible).fetchToken()— newscopeoptionThe function now accepts an explicit
scopeoption.authorization_codevia built-inprepareAuthorizationCodeRequestscopeis forwarded.clientMetadata.scopeis never injected. This preventsinvalid_scopefrom servers that narrowed the grant during authorization (RFC 6749 §4.1.3).prepareTokenRequest()(client_credentials, jwt-bearer, …)provider.clientMetadata.scopeas before, because these flows start a fresh request rather than redeeming a pre-authorized grant.auth()—tokenExchangeScopeauth()now computes a separatetokenExchangeScope = scope(the raw scope from theWWW-Authenticatechallenge, if any). It passes only that explicit server-provided value intofetchToken(), so neither PRMscopes_supportednorclientMetadata.scopeare re-injected at the token-exchange step.resolvedScope(the full fallback chain: WWW-Authenticate → PRM → clientMetadata) continues to be used for DCR and the authorization redirect, as before.Test Coverage
prepareAuthorizationCodeRequest: includes scope when provided; omits scope when not provided.fetchToken: explicit scope reaches the token body; no scope injection fromclientMetadatawhen called without explicit scope.exchangeAuthorization/ fullauth()tests continue to pass unchanged.Compatibility
No breaking changes. All existing call sites that do not pass
scopetoprepareAuthorizationCodeRequestorfetchTokenbehave identically to before.