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Fix CreateMessageRequestParams.Metadata type to JsonObject

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1354

#1354 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 23, 2026

API Review / Approval of MCP C# SDK APIs

Status: Closed (completed).

#213 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Feb 5, 2026

Don't create sessions for requests without a sessionId

bugSomething isn't workingSomething isn't working

Status: Closed (completed).

#1000 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Feb 19, 2026

Add global transport-level filters

enhancementNew feature or requestNew feature or request

Status: Closed (completed).

#761 In modelcontextprotocol/csharp-sdk;

· by halter73 was closed on Feb 3, 2026

Experimental APIs force users to suppress diagnostics even when they are not used

Status: Closed (completed).

#1255 In modelcontextprotocol/csharp-sdk;

· by MackinnonBuck was closed on Feb 19, 2026

Fix HttpClient timeout for long-running tools without event stream store

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1268

#1268 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 14, 2026

Split configuration of request and message filters

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1308

#1308 In modelcontextprotocol/csharp-sdk;

· by halter73 was closed on Feb 20, 2026

Add docs for working with experimental APIs

documentationImprovements or additions to documentationImprovements or additions to documentation

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1307

#1307 In modelcontextprotocol/csharp-sdk;

· by MackinnonBuck was closed on Feb 19, 2026

Validate MCP-Protocol-Version header in Streamable HTTP handler

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1277

#1277 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 19, 2026

Change ProtectedResourceMetadata URI properties to strings and build resource strings directly

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1264

#1264 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 13, 2026

Update McpErrorCode XML docs and fix error code usage to align with MCP spec

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1291

#1291 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 17, 2026

Remove LegacyTitledEnumSchema API

Status: Closed (abandoned).

modelcontextprotocol/csharp-sdknumber 1309

#1309 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 19, 2026

Add ISessionMigrationHandler

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1270

#1270 In modelcontextprotocol/csharp-sdk;

· by MackinnonBuck was closed on Feb 19, 2026

Don't treat McpServerHandlers as an independent options type

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1313

#1313 In modelcontextprotocol/csharp-sdk;

· by halter73 was closed on Feb 19, 2026

Use ReadOnlyMemory<byte> for binary data to eliminate UTF-16 transcoding

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1070

#1070 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 19, 2026

Replace concrete collection types with interfaces in public API surface

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1326

#1326 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 20, 2026

Make UrlElicitationRequiredErrorData.Elicitations consistent with other Protocol DTOs

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1335

#1335 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 21, 2026

Fix Metadata delegation in DelegatingMcpServerTool/Prompt/Resource

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1338

#1338 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 21, 2026

Unable to assign handlers to McpServerOptions.Handlers after upgrading to v0.9.0 (readonly regression?)

bugSomething isn't workingSomething isn't working

P2Moderate issues, valuable feature requestsModerate issues, valuable feature requests

ready for workHas enough information to startHas enough information to start

Status: Closed (completed).

#1331 In modelcontextprotocol/csharp-sdk;

· by gabaoalb was closed on Feb 23, 2026

Address asymmetry in McpServerHandlers/McpClientHandlers and make all filter properties settable

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1337

#1337 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 23, 2026

0.9.0-preview.1: ImageContentBlock throws "invalid base64" when consuming CallToolResult (works in 0.8.0-preview.1)

bugSomething isn't workingSomething isn't working

P1Significant bug affecting many usersSignificant bug affecting many users

ready for workHas enough information to startHas enough information to start

Status: Closed (completed).

#1340 In modelcontextprotocol/csharp-sdk;

· by monikbhatt was closed on Feb 23, 2026

Fix _meta properties to use JsonObject

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1341

#1341 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 21, 2026

Remove server back-references from protocol DTO types

breaking-changeThis issue or PR introduces a breaking changeThis issue or PR introduces a breaking change

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1345

#1345 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 23, 2026

Fix base64 deserialization when JSON encoder escapes forward slashes

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1342

#1342 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 23, 2026

Add CloneResourceMetadataClonesAllProperties test using public reflection

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1343

#1343 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Feb 23, 2026