All four Tier 1 MCP SDKs shipped stable 2026-07-28 support within a day of the revision

All four Tier 1 SDKs shipped stable support for the 2026-07-28 revision on or within a day of its release. The TypeScript SDK led by a day: nine @modelcontextprotocol/* packages were published at 2.0.0 on July 27, with the core release notes stating support for the revision. The Python SDK's mcp v2.0.0 and the Go SDK's v1.7.0 followed on the morning of July 28, and the C# SDK's v2.0.0 landed that evening.

Each SDK handles the stateless core differently at the configuration layer. Python v2.0.0 serves every earlier revision from the same server alongside 2026-07-28. Go v1.7.0 accepts requests at protocol version 2026-07-28 only when StreamableHTTPOptions.Stateless = true, otherwise clients negotiate down to 2025-11-25; it removes ping, logging/setLevel, resources/subscribe, and resources/unsubscribe on the new revision, and gates seven behavior reversions behind MCPGODEBUG flags that the release notes say will all be removed in v1.9.0. C# v2.0.0 flips HttpServerTransportOptions.Stateless to default true, marks Roots, Sampling, and Logging API surfaces with MCP9005 warnings, and moves Tasks into a separate ModelContextProtocol.Extensions.Tasks package with no API or wire compatibility with the earlier experimental implementation.

The Go release notes cite production validation: the v1.7.0-pre.3 prerelease "is already successfully used by GitHub, serving more than half a million users", the maintainers' characterization of the GitHub MCP Server deployment that shipped ahead of the revision.

Beyond Tier 1, the Rust SDK published a stable rmcp 3.0.0 to crates.io at 22:52 UTC the same day, roughly six hours after the official release announcement described Rust support as beta, with follow-ups 3.0.1 and 3.1.0 landing the same week. None of the three releases has been yanked.