modelcontextprotocol / modelcontextprotocol/php-sdk
[2026-07-28] Authorization hardening (OAuth/OIDC)
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- Dominant language
- PHP
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Description
Tracking issue for the MCP Spec 2026-07-28 release — Authorization hardening milestone.
Most of this milestone overlaps with the existing client-OAuth backlog (#315–#326). New SEP-specific work concentrates on issuer validation, AS-binding semantics, server-side scope emission, and OIDC offline_access handling.
SEPs covered
| SEP | Title | Spec PR | Coverage |
|---|---|---|---|
| SEP-2468 | Recommend iss Parameter (RFC 9207) |
#2468 | New issue |
| SEP-2352 | Authorization Server binding and migration | #2352 | New issue |
| SEP-2351 | RFC 8414 well-known URI suffix | #2351 | Covered by #318 |
| SEP-2350 | Client-side scope accumulation in step-up | #2350 | Client covered by #322; new server-side issue |
| SEP-2207 | OIDC-flavored refresh token guidance | #2207 | New issues (client + server) |
| SEP-837 | OIDC application_type during DCR |
#837 | Covered by #320 + #321 |
Sub-issues
- #360 — SEP-2468: Validate
issparameter in authorization response (client) - #361 — SEP-2352: Key DCR/tokens by AS issuer; reject cross-AS reuse (client)
- #362 — SEP-2350: Emit per-operation scopes in
insufficient_scope403 responses (server) - #363 — SEP-2207: Request
offline_accessagainst OIDC-flavored AS (client) - #364 — SEP-2207: Audit PRM to ensure
offline_accessis not advertised as required (server)
Existing issues to annotate with SEP refs
- #315 (TokenStorage) → SEP-2352
- #318 (RFC 8414 AS metadata) → SEP-2351
- #319 (Auth Code + PKCE) → SEP-2468, SEP-2207
- #320 (DCR) → SEP-2352, SEP-837
- #321 (token_endpoint_auth_method) → SEP-837
- #322 (scope handling/step-up) → SEP-2350
- #323 (refresh_token grant) → SEP-2207
Notes
- All six SEPs are merged.
- PHP SDK client-side OAuth is largely unimplemented; the bulk of work is therefore on the client side via the existing #315–#326 backlog plus the new SEP-specific issues above. Server-side OAuth middleware needs targeted PRM/
WWW-Authenticateaudits only.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reviewing sub-issues #360–#364 and the related OAuth backlog #315–#326, then read the linked SEP references and existing authorization implementation. This tracking issue is complete when its five sub-issues are resolved and the listed PRM and WWW-Authenticate audits are finished.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- php
- Domain
- authentication, security
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Quiet
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100