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feat(mcp-core): support Mcp-Name header for Streamable HTTP (SEP-2243) - #994

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cooleditphoto:feature/SEP-2243-Mcp-Name-in-header
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feat(mcp-core): support Mcp-Name header for Streamable HTTP (SEP-2243)#994
cooleditphoto wants to merge 10 commits into
modelcontextprotocol:mainfrom
cooleditphoto:feature/SEP-2243-Mcp-Name-in-header

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@cooleditphoto

@cooleditphoto cooleditphoto commented Jun 3, 2026 •
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Add MCP_NAME header constant and inject it in the streamable HTTP client transport (HttpClientStreamableHttpTransport) and HTTP server transport

Motivation and Context

#990
To solve the Mcp_Name part of https://modelcontextprotocol.io/seps/2243-http-standardization

How Has This Been Tested?

[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 04:44 min
[INFO] Finished at: 2026-06-02T09:02:38-04:00
[INFO] ------------------------------------------------------------------------

Breaking Changes

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Documentation update

Checklist

  • I have read the MCP Documentation
  • My code follows the repository's style guidelines
  • New and existing tests pass locally
  • I have added appropriate error handling
  • I have added or updated documentation as needed

Additional context

@cooleditphoto
feat(mcp-core): support Mcp-Name header for Streamable HTTP (SEP-2243)
4f1052a 
Add MCP_NAME header constant and inject it in the streamable HTTP client transport (HttpClientStreamableHttpTransport)
@cooleditphoto
Merge branch 'main' into feature/SEP-2243-Mcp-Name-in-header
f229279
This was referenced Jun 12, 2026
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@Kehrlann
Kehrlann self-requested a review June 24, 2026 12:49
@Kehrlann Kehrlann self-assigned this Jun 24, 2026
@Kehrlann

Kehrlann commented Jun 24, 2026

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Hey @cooleditphoto ! Thanks for your contribution.

A few remarks:

  • This PR breaks backwards client/server compatibility. Servers cannot afford to reject non-compliant clients directly. We could allow users to configure their users so that they reject requests without the headers, but it shouldn't be the default.
  • This PR has no test coverage.
  • This does not cover SEP-2243 entirely, which makes tracking 2243 implementation complicated

@cooleditphoto

cooleditphoto commented Jul 20, 2026

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@Kehrlann I addressed your comments.

@Kehrlann Kehrlann added this to the 3.x Planning milestone Aug 7, 2026
@slachiewicz slachiewicz mentioned this pull request Aug 27, 2026
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@slachiewicz

slachiewicz commented Aug 28, 2026

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Flagging an overlap so it doesn't get discovered at merge time: #1112 (mine, still draft) also implements Mcp-Name, and touches three of the same files as this PR — HttpClientStreamableHttpTransport, HttpServletStreamableServerTransportProvider and HttpHeaders. #1026 covers the Mcp-Method half on two of them. Three open PRs against #990.

This one is furthest along and already has review on it, so I'd rather not cut across it. I'm happy to strip Mcp-Name out of #1112 and rebase what's left — the protocol-version validation and the server-side header/body consistency checks — on top of this once it lands. Say the word and I'll do that rather than have maintainers reconcile three diffs.

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@Kehrlann Kehrlann Awaiting requested review from Kehrlann

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@Kehrlann Kehrlann

Labels

area/client area/server enhancement New feature or request

Projects

2026-07-28 Spec Implementation
Status: Todo

Milestone

3.x Planning

Development

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3 participants

@cooleditphoto @Kehrlann @slachiewicz