typescript-sdk/.changeset/dpop-client-tokens.md

@modelcontextprotocol/client	@modelcontextprotocol/core
minor	minor

Add DPoP (RFC 9449 / SEP-1932) sender-constrained access token support to the client.

• Opt in by implementing OAuthClientProvider.dpop() returning a DpopSession (new, along with generateDpopKeyPair, accessTokenHash, isDpopNonceChallenge). auth() / exchangeAuthorization / refreshAuthorization / fetchToken then sign a DPoP proof into token requests (retrying once on an authorization-server use_dpop_nonce challenge, with client authentication re-applied per attempt), and StreamableHTTPClientTransport, SSEClientTransport and withOAuth present a token_type: "DPoP" access token as Authorization: DPoP <token> plus a fresh per-request proof, retry a resource-server use_dpop_nonce challenge once, and pick up a DPoP-Nonce delivered on any response. Tokens the AS issued as Bearer are still presented as Bearer.
• DPoP is applied at the fetch layer: the transports wrap their resource-server fetch (including a caller-supplied fetch / eventSourceInit.fetch) with the new withDpopFromProvider(provider) middleware, so proofs are always bound to the request actually sent. withDpop(session, getToken) is exported for callers that manage tokens themselves (e.g. alongside a minimal AuthProvider); the AuthProvider interface itself is unchanged.
• auth() now recovers from invalid_dpop_proof on refresh (e.g. a refresh token bound to a key that is no longer held) by discarding the tokens and re-authorizing, like invalid_grant. OAuthErrorCode gains InvalidDpopProof and UseDpopNonce; extractWWWAuthenticateParams recognizes the DPoP challenge scheme; OAuthMetadataSchema gains dpop_signing_alg_values_supported.