MCP Roadmap Targets HTTP/2 Over stdio to Kill the Two-Transport Split

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The Transports WG will attempt to make Streamable HTTP the single binding for MCP, spoken over stdin/stdout for local servers using HTTP/2 for multiplexing while keeping subprocess security and lifecycle guarantees. The stated problem is that every HTTP-native feature currently needs a second stdio-specific design, SDKs maintain two pipelines, and protocol metadata is duplicated across HTTP headers and message fields that servers must cross-validate. The same area adds ETag support on top of the 2026-07-28 release's ttlMs and cacheScope caching (SEP-2549), extending versioning to tool call results.