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Add tests for Base64 related encoding logic in Content, Resource, and MEAI-AIContent conversion paths

Status: Open.

#1360 In modelcontextprotocol/csharp-sdk;

· ericstj opened 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: Open.

#1340 In modelcontextprotocol/csharp-sdk;

· monikbhatt opened on Feb 21, 2026

·  

1.0.0 (GA)

Stdio transport does not expose process exit code on server launch failure

P2Moderate issues, valuable feature requestsModerate issues, valuable feature requests

ready for workHas enough information to startHas enough information to start

Status: Open.

#1332 In modelcontextprotocol/csharp-sdk;

· hulumane opened on Feb 20, 2026

·  

Future Minor Version

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: Open.

#1331 In modelcontextprotocol/csharp-sdk;

· gabaoalb opened on Feb 20, 2026

·  

1.0.0 (GA)

Opt in to <code>EnablePackageValidation</code> to catch breaking changes

area-infrastructureRelated to repo infrastructureRelated to repo infrastructure

ready for workHas enough information to startHas enough information to start

Status: Open.

#1329 In modelcontextprotocol/csharp-sdk;

· jeffhandley opened on Feb 20, 2026

More string intermediates in read side if MCP transport

enhancementNew feature or requestNew feature or request

needs confirmationUnclear if still relevantUnclear if still relevant

P3Nice to haves, rare edge casesNice to haves, rare edge cases

Status: Open.

#1318 In modelcontextprotocol/csharp-sdk;

· ericstj opened on Feb 19, 2026

Custom filters

enhancementNew feature or requestNew feature or request

P3Nice to haves, rare edge casesNice to haves, rare edge cases

ready for workHas enough information to startHas enough information to start

Status: Open.

#1314 In modelcontextprotocol/csharp-sdk;

· herbat73 opened on Feb 19, 2026

·  

Future Minor Version

Add DeleteStreamsForSessionAsync to ISseEventStreamStore

enhancementNew feature or requestNew feature or request

P3Nice to haves, rare edge casesNice to haves, rare edge cases

ready for workHas enough information to startHas enough information to start

Status: Open.

#1287 In modelcontextprotocol/csharp-sdk;

· mikekistler opened on Feb 16, 2026

·  

Future Minor Version

ObjectDisposedException - IServiceProvider disposed while tool handler execution.

bugSomething isn't workingSomething isn't working

ready for workHas enough information to startHas enough information to start

Status: Open.

#1269 In modelcontextprotocol/csharp-sdk;

· r-Larch opened on Feb 14, 2026

Support specifying OutputSchema type independently of return type for tools returning CallToolResult

enhancementNew feature or requestNew feature or request

ready for workHas enough information to startHas enough information to start

Status: Open.

#1263 In modelcontextprotocol/csharp-sdk;

· jcauv4 opened on Feb 11, 2026

Returning an EmbeddedResourceBlock from a tool do not work with Claude Desktop

needs confirmationUnclear if still relevantUnclear if still relevant

Status: Open.

#1261 In modelcontextprotocol/csharp-sdk;

· eng-marani opened on Feb 11, 2026

notifications/tools/list_changed handler apparently times out over Streamable HTTP

bugSomething isn't workingSomething isn't working

Status: Open.

#1239 In modelcontextprotocol/csharp-sdk;

· janwilch opened on Feb 3, 2026