modelcontextprotocol / modelcontextprotocol/php-sdk

[2026-07-28] Transport & observability headers/metadata

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2026-07-28 Client enhancement improves spec compliance Schema Server
Dominant language
PHP
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Avg merge
2d 49m
Merged PRs (30d)
23

Description

Tracking issue for the MCP Spec 2026-07-28 release — Transport & observability milestone.

Additive, non-breaking changes that surface routing/observability hints at the transport layer.

SEPs covered

SEP Title Spec PR
SEP-2243 HTTP Standardization (Mcp-Method / Mcp-Name headers) #2243
SEP-2549 TTL for List Results (ttlMs / cacheScope) #2549
SEP-414 OpenTelemetry Trace Context Propagation #414

Sub-issues

  • #353 — SEP-2243: Emit Mcp-Method and Mcp-Name HTTP headers (server + client)
  • #354 — SEP-2549: ttlMs and cacheScope on list/read results
  • #355 — SEP-414: W3C Trace Context propagation via _meta (server + client)

Notes

  • All three SEPs are merged.
  • All three are additive — implementable independently of the Milestone A stateless overhaul, though SEP-2243 should be gated on the per-request protocol version introduced in SEP-2575 (#340).

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with sub-issues #353, #354, and #355, then read their linked merged SEPs and spec PRs. For #353, check the per-request protocol version from #340 before implementing headers; for #354 and #355, follow the listed result metadata and trace-context requirements. Done means the applicable server and client changes for all three transport and observability features are implemented independently.

Written by the indexing model from the issue text.

Assessment

Tech stack
php
Domain
api, backend, observability
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
35/100

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