[v2] Spec mismatch: error when io.modelcontextprotocol/clientInfo is missing #2537

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1. tobiasBora

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   v2Ideas, requests and plans for v2 of the SDK which will incorporate major changes and fixesIdeas, requests and plans for v2 of the SDK which will incorporate major changes and fixes

   on Jul 23, 2026
2. felixweinberger commented on Jul 23, 2026

   

   felixweinberger

   on Jul 23, 2026

   Last edited by felixweinberger

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   This should be resolved in beta.5, this was a late breaking spec change in modelcontextprotocol/modelcontextprotocol#3002

   PR: #2513

   👍React with 👍1Reacted by Tobias Bora
3. felixweinberger

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   needs confirmationNeeds confirmation that the PR is actually required or needed.Needs confirmation that the PR is actually required or needed.

   on Jul 23, 2026
4. claude commented on Aug 19, 2026

   

   claudebot

   on Aug 19, 2026 – with Claude

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   Closing: fixed in #2513, released in 2.0.0-beta.5

   Thanks for the report! This came from a late-breaking spec change — modelcontextprotocol/modelcontextprotocol#3002 demoted the request envelope's io.modelcontextprotocol/clientInfo from required to SHOULD — and the server-side rejection you hit was fixed in #2513 (merged 2026-07-20), which makes clientInfo optional in the _meta envelope exactly as the final 2026-07-28 revision requires. That fix shipped in 2.0.0-beta.5 (released 2026-07-21) and is included in the stable 2.0.0 release; the report was against 2.0.0-beta.4, which predates it. Upgrading to 2.0.0 (or any release from beta.5 onward) resolves the error — if you still see it there, please open a new issue.

   This comment and close were reviewed and approved by maintainer @felixweinberger — it is a human-approved action, not an unattended automated one.

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5. claude

   closed this as completedon Aug 19, 2026