C# SDK v2.1.0 adds a public subscriptions/listen server handler and HTTP transport fallback fixes
The C# SDK published v2.1.0, its first release since v2.0.0 on 2026-07-28. It adds a public server-side handler for the subscriptions/listen method introduced by SEP-2575, and makes a client fall back to initialize when server/discover fails at the HTTP layer.
The C# SDK published tag v2.1.0 on August 5 (2026-08-05T03:49:08Z,
created 2026-08-05T03:29:59Z), prerelease: false, release author
jeffhandley. It is the first release since v2.0.0 on 2026-07-28.
Release notes list a public subscriptions/listen server handler
(SEP-2575, PR #1775 by @tarekgh), a client fallback to initialize when
server/discover fails at the HTTP layer (PR #1766 by @rbstp), and two
HTTP transport fixes by @PranavSenthilnathan: keeping the AutoDetect
channel open after provisional SSE failure, and preserving HTTP status
codes across target frameworks.
Five NuGet package ids ship at 2.1.0, each with .nupkg and .snupkg
assets: ModelContextProtocol, ModelContextProtocol.Core,
ModelContextProtocol.AspNetCore,
ModelContextProtocol.Extensions.Apps, and
ModelContextProtocol.Extensions.Tasks. PR #1775 itself merged on
August 4; only its shipping in v2.1.0 is in this window.
Related spec revisions
- MCP 2026-07-28 - current
How was this verified, and what are the sources?
Published · last verified · confidence 0.90.
- GitHub release page for modelcontextprotocol/csharp-sdk v2.1.0; observed published_at, the four changelog lines with PR numbers and authors, and all ten attached package assets - accessed
- csharp-sdk merged-PR search for merged:2026-08-04..2026-08-06, total_count 9, with per-PR closed_at timestamps - accessed