[dependabot]

Updated ModelContextProtocol.Core from 2.2.0 to 2.3.0.

Release notes

Sourced from ModelContextProtocol.Core's releases.

2.3.0

This release improves HTTP discovery, OAuth, protocol interoperability, and shutdown reliability, preserves registration order for server primitives, and exposes a TimeProvider for deterministic client timeout tests. It also corrects optional server-identity handling; applications reading McpClient.ServerInfo should adopt nullable handling.

Breaking Changes

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

1. McpClient.ServerInfo is nullable — #​1903
   • Its return annotation changes from Implementation to Implementation?. Existing non-nullable assignments or dereferences can produce nullable warnings and fail warnings-as-errors builds.
   • On 2026-07-28 connections, ServerInfo is null when the server omits optional identity metadata from server/discover. Legacy initialize still requires serverInfo. Reading the property before connecting still throws InvalidOperationException.
   • Migrate with a null check or a fallback such as client.ServerInfo?.Name ?? "Unknown server". Self-reported identity must not be used for security decisions.
   • This corrective source-compatibility change is intentionally included in 2.3.0.

What's Changed

• Correct protocol-version telemetry for stateless server spans #​1810 by @​luisangelrod
• Preserve HTTP errors and correct discovery fallback handling #​1791 by @​PranavSenthilnathan (co-authored by @​Copilot)
• Make modern Streamable HTTP status mapping deterministic #​1837 by @​jstar0
  • Modern responses wait for the first protocol message before sending headers; long-running silent handlers may need progress output or an appropriate HTTP timeout. Legacy eager-header behavior is preserved.
• Accept opaque legacy metadata and correct request-scoped capabilities and discovery advertisement #​1852 by @​halter73 (co-authored by @​Copilot)
• Avoid redundant SSE fallback after discovery is rejected with 400 or 404 #​1855 by @​scottt732
• Close server stdin before waiting for graceful stdio process exit #​1838 by @​luisangelrod
• Preserve insertion order when listing server tools, prompts, and resources #​1924 by @​PederHP (co-authored by Claude Opus 5.5)
• Allow missing optional server identity in discovery and make ServerInfo nullable #​1903 by @​Coding-Professional
• Include JSON parse details in Streamable HTTP 400 responses #​1844 by @​ump45nose
• Exclude OAuth from DiscoverProbeTimeout, expose McpClientOptions.TimeProvider for deterministic timeout tests, and default SSE to legacy initialization #​1719 by @​halter73 (co-authored by @​Copilot)
  • OAuth remains subject to the overall InitializationTimeout and caller cancellation; it is excluded only from the short discovery-probe budget.
  • Modern discovery over SSE requires both explicit HttpTransportMode.Sse and ProtocolVersion = "2026-07-28"; pinning the version with AutoDetect is not equivalent.
• Preserve numeric progress tokens in RequestOptions serialization #​1832 by @​dfedoryshchev
• Dispose legacy SSE POST responses to release connections deterministically #​1841 by @​yalcinfu22 (co-authored by Claude Fable 5)

Documentation Updates

• Document standing support for new MCP specification revisions #​1826 by @​halter73 (co-authored by @​Copilot)

Test Improvements

• Stabilize discovery-capable test connections while retaining initialization deadlines #​1943 by @​tarekgh

Repository Infrastructure Updates

• Add a source selector for manual documentation publishes #​1828 by @​jeffhandley (co-authored by @​Copilot)
• Update SourceLink's private build dependency to resolve a vulnerable Git dependency #​1873 by @​halter73 (co-authored by @​Copilot)
• Correct obsolete McpServerFactory references in Copilot instructions #​1892 by @​Zir0-93
• Update Microsoft.Extensions.AI and AI.Abstractions to 10.11.0 and align shared System dependencies to 10.0.13 #​1940

Acknowledgements

• @​scottt732 made their first contribution in #​1855
• @​Zir0-93 made their first contribution in #​1892
• @​Coding-Professional made their first contribution in #​1903
  ... (truncated)

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