v2.0.0-rc.2

This second 2.0 release candidate advances the SDK’s 2026-07-28 protocol support, expands Tasks extension conformance tests, strengthens OAuth and transport behavior, and expands 2.0 guidance ahead of general availability.

Thank you to the community for using the preview and release-candidate builds and for sharing feedback and issue reports that shape this release!

Breaking Changes

Refer to the C# SDK Versioning documentation for details on versioning and breaking-change policies.

1. Align the 2026-07-28 wire protocol and SEP-2575 HTTP statuses #1752
   • Aligns with protocol adjustment #3002.
   • DiscoverResult.ServerInfo is removed; read and deserialize Meta[MetaKeys.ServerInfo] instead.
   • On 2026-07-28, replace legacy initialization, ping, logging, and resource-subscription methods with server/discover, _meta log level, and subscriptions/listen.
2. Validate OAuth authorization state #1726
   • Custom authorization callback handlers must propagate the redirect state through AuthorizationResult.State, and should return Code, State, and Iss.
3. Fix SSE session transport shutdown behavior #1432
   • Handle the underlying transport exception rather than depending on an IOException wrapper.

What's Changed

• Fix SSE session transport shutdown behavior #1432 by @xue-cai (co-authored by @Copilot)
• Validate OAuth authorization state #1726 by @halter73 (co-authored by @Copilot)
• Add configurable Tasks execution modes and complete conformance support #1741 by @PranavSenthilnathan (co-authored by @Copilot)
• Gate 2026-07-28 result fields by negotiated protocol version #1753 by @tarekgh
• Align the 2026-07-28 wire protocol and SEP-2575 HTTP statuses #1752 by @pcarleton (co-authored by @tarekgh @Copilot)
• Reauthorize tools changed by call-tool filters #1737 by @PranavSenthilnathan (co-authored by @Copilot)

Documentation Updates

• Refine 2.0.0 concept documentation #1742 by @jeffhandley (co-authored by @Copilot)

Test Improvements

• Resolve test-server paths deterministically #1735 by @PranavSenthilnathan (co-authored by @Copilot)
• Add MCP Apps NativeAOT coverage #1711 by @lntutor
• Add MCP Apps _meta.ui serialization round-trip tests #1698 by @yayayouyou

Repository Infrastructure Updates

• Bump actions/setup-node from 6.4.0 to 7.0.0 #1717
• Bump coverlet.collector from 10.0.0 to 10.0.1 #1582
• Bump qs from 6.14.2 to 6.15.2 #1597
• Bump actions/setup-dotnet from 5.2.0 to 6.0.0 #1716
• Bump danielpalme/ReportGenerator-GitHub-Action from 5.5.5 to 5.5.10 #1569
• Bump actions/checkout from 6 to 7 #1665
• Rename MCPEXP002 extensibility constants #1739 by @arimu1
• Bump the testing-frameworks group #1746
• Bump the serilog-testing group #1748
• Bump actions/checkout from 7.0.0 to 7.0.1 #1745
• Bump Anthropic from 12.17.0 to 12.39.0 #1750
• Bump OpenTelemetry and five other dependencies #1747
• Bump JsonSchema.Net and System.Linq.AsyncEnumerable #1749
• Update Microsoft.Extensions.AI dependencies #1755 by @jeffhandley (co-authored by @Copilot)
• Add AI disclosure guidance #1756 by @PranavSenthilnathan (co-authored by @Copilot)

Acknowledgements

• @lntutor, @arimu1, @yayayouyou, and @xue-cai made their first contributions in #1711, #1739, #1698, and #1432.
• @p-ob reported #1721, resolved by #1753.
• @pcarleton initiated #1752 to address the SEP-2575 revision.
• @jeffhandley @PranavSenthilnathan @halter73 @tarekgh @jozkee reviewed pull requests.

Full Changelog: v2.0.0-rc.1...v2.0.0-rc.2