Release v2.0.0-rc.2

[jeffhandley]

Release v2.0.0-rc.2

This second 2.0 release candidate advances the SDK’s 2026-07-28 protocol support, completes Tasks extension conformance, and strengthens OAuth and transport behavior 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.

Release Notes

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 Align the 2026-07-28 wire with spec PR #3002 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 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 Fix: swallow _receiveTask exceptions in SseClientSessionTransport.CloseAsync #1432
   • Handle the underlying transport exception rather than depending on an IOException wrapper.

What's Changed

• Fix SSE session transport shutdown behavior Fix: swallow _receiveTask exceptions in SseClientSessionTransport.CloseAsync #1432 by @xue-cai (co-authored by @copilot)
• Validate OAuth authorization state Validate OAuth authorization state #1726 by @halter73 (co-authored by @copilot)
• Add configurable Tasks execution modes and complete conformance support Enable complete Tasks extension conformance coverage #1741 by @PranavSenthilnathan (co-authored by @copilot)
• Gate 2026-07-28 result fields by negotiated protocol version Gate 2026-07-28 result fields on negotiated protocol version (#1721) #1753 by @tarekgh
• Align the 2026-07-28 wire protocol and SEP-2575 HTTP statuses Align the 2026-07-28 wire with spec PR #3002 and SEP-2575 HTTP statuses #1752 by @pcarleton (co-authored by @tarekgh @copilot)
• Reauthorize tools changed by call-tool filters Reauthorize tools changed by call-tool filters #1737 by @PranavSenthilnathan (co-authored by @copilot)

Test Improvements

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

Repository Infrastructure Updates

• Bump actions/setup-node from 6.4.0 to 7.0.0 Bump actions/setup-node from 6.4.0 to 7.0.0 #1717
• Bump coverlet.collector from 10.0.0 to 10.0.1 Bump coverlet.collector from 10.0.0 to 10.0.1 #1582
• Bump qs from 6.14.2 to 6.15.2 Bump qs from 6.14.2 to 6.15.2 in the npm_and_yarn group across 1 directory #1597
• Bump actions/setup-dotnet from 5.2.0 to 6.0.0 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 Bump danielpalme/ReportGenerator-GitHub-Action from 5.5.5 to 5.5.10 #1569
• Bump actions/checkout from 6 to 7 Bump actions/checkout from 6 to 7 #1665
• Rename MCPEXP002 extensibility constants Rename MCPEXP002 Subclassing_* constants to Extensibility_* #1739 by @arimu1
• Bump the testing-frameworks group Bump the testing-frameworks group with 1 update #1746
• Bump the serilog-testing group Bump the serilog-testing group with 1 update #1748
• Bump actions/checkout from 7.0.0 to 7.0.1 Bump actions/checkout from 7.0.0 to 7.0.1 #1745
• Bump Anthropic from 12.17.0 to 12.39.0 Bump Anthropic from 12.17.0 to 12.39.0 #1750
• Bump OpenTelemetry and five other dependencies Bump OpenTelemetry and 5 others #1747
• Bump JsonSchema.Net and System.Linq.AsyncEnumerable Bump JsonSchema.Net and System.Linq.AsyncEnumerable #1749
• Update Microsoft.Extensions.AI dependencies Update Microsoft.Extensions.AI dependencies #1755 by @jeffhandley (co-authored by @copilot)

Acknowledgements

• @lntutor, @arimu1, @yayayouyou, and @xue-cai made their first contributions in Add MCP Apps to NativeAOT coverage #1711, Rename MCPEXP002 Subclassing_* constants to Extensibility_* #1739, Add round-trip integration tests for MCP Apps _meta.ui serialization #1698, and Fix: swallow _receiveTask exceptions in SseClientSessionTransport.CloseAsync #1432.
• @p-ob reported bug(2.0.0-preview.3): resultType, ttlMs, and cacheScope emitted on all responses regardless of negotiated protocol version (breaks 2025-11-25 clients) #1721, resolved by Gate 2026-07-28 result fields on negotiated protocol version (#1721) #1753.
• @pcarleton initiated Align the 2026-07-28 wire with spec PR #3002 and SEP-2575 HTTP statuses #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

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API Compatibility Report

Package validation completed without compatibility diagnostics or new suppressions.

API Diff Report

ModelContextProtocol.Core

+ AuthorizationResult.State
- DiscoverResult.ServerInfo
+ MetaKeys.ServerInfo
+ StreamableHttpServerTransport.HandlePostRequestAsync(...)

ModelContextProtocol

No standalone public API changes.

ModelContextProtocol.AspNetCore

No standalone public API changes.