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fix(mcp): handle refresh_token grant in the consent proxy /token endpoint - #2701
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…oint Live PROD failure (2026-10-08) after a SUCCESSFUL initial auth: on reconnect mcp-remote POSTs grant_type=refresh_token to our /token, but handleToken only accepted authorization_code → 400 "unsupported_grant_type" on every refresh. The discovery doc advertises refresh_token in grant_types_supported, and we pass IAS's refresh_token through to the client verbatim at the code exchange — so the client correctly tries to refresh against us (its advertised AS). We just never implemented the branch. Fix: add an idpRefresh() boundary (mirrors idpExchange) that relays the client's refresh_token to IAS /oauth2/token with grant_type=refresh_token + the client's own client_id (public client, no secret, no PKCE on refresh). handleToken now branches: refresh_token → idpRefresh; authorization_code → unchanged; anything else → unsupported_grant_type. Passes rotated refresh_token through, falls back to the old one when IAS doesn't rotate. Tests: +6 (refresh proxy happy path, rotation + no-rotation fallback, missing refresh_token 400, IAS-failure 400, real idpRefresh body with fetch mocked). 31 unit tests green.
jung-thomas
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October 8, 2026 22:24
jung-thomas
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Oct 9, 2026
Resolves the 1.37.0 vs 1.37.1 overlap on the two release-managed files: - .deploy/mta.yaml: keep 1.37.1 (supersedes main's 1.37.0 bump). - hugo/data/whats_new.json: keep the 757-entry digest, which already incorporates main's 752-entry 1.37.0 digest (rebased onto it) plus the 4 new 1.37.1 PRs (#2700/#2701/#2704/#2705). Verified superset: all 1.37.0 entries retained, 4 new entries added, no duplicates.
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What
Adds the
refresh_tokengrant to the consent proxy's/tokenendpoint. Without it, mcp-remote fails on reconnect withunsupported_grant_typeeven though the initial auth succeeded.Live symptom (PROD, 2026-10-08)
Browser consent + IAS login succeeded, initial token issued, transport connected. Then on reconnect:
OAuthError2: unsupported_grant_typefromrefreshAuthorization→executeTokenRequest.Root cause
handleTokenonly acceptedgrant_type=authorization_code. But the discovery doc advertisesrefresh_tokeningrant_types_supported, and we pass IAS'srefresh_tokenthrough to the client verbatim — so the client refreshes against us (its advertised AS). The branch was never implemented → hard 400 on every refresh.Fix
idpRefresh()boundary (mirrorsidpExchange): relays the client'srefresh_tokento IAS/oauth2/tokenwith the client's ownclient_id(public client, no secret, no PKCE on refresh).handleTokenbranches:refresh_token→idpRefresh;authorization_code→ unchanged; else →unsupported_grant_type.refresh_tokenthrough; falls back to the old one when IAS doesn't rotate.Tests
+6: refresh happy path, rotation + no-rotation fallback, missing refresh_token (400), IAS-failure (400), and the real
idpRefreshbody withfetchmocked (the kind of test that caught the last regression). 31 green.Chain
5th consent fix: #2691 + #2693 + #2696 + #2697 + #2698 + this. After deploy, the full mcp-remote lifecycle (auth → use → token refresh → reconnect) completes.