modelcontextprotocol/csharp-sdk

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The official C# SDK for Model Context Protocol servers and clients. Maintained in collaboration with Microsoft.

Stars: 4.5k
Forks: 814
Open beginner issues: 1
Indexed issues: 126
Avg merge: 9d 19h
Merged PRs (30d): 4

Dominant language: C#
License: No license data
Last GitHub push: Sep 19, 2026
Latest indexed: Sep 20, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: help wanted

Beginner friendly Everything

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126 open issues indexed

[Proposal] Declarative tool registration & runtime filtering for version gating (#1557) Open

Difficulty 5/5 Over a week Newbie friendliness 28/100

modelcontextprotocol/csharp-sdk#1881 · Opened Sep 17, 2026
MCP Client: Add bounded connection-establishment recovery with end-to-end timeout and closure guarantees Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 38/100

modelcontextprotocol/csharp-sdk#1879 · Opened Sep 16, 2026
csharp-sdk graded A (93/100) on OpenTrustBench, badge inside Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

modelcontextprotocol/csharp-sdk#1871 · Opened Sep 11, 2026
MCP Protocol-Version Ceiling for the C# Client SDK Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 45/100

modelcontextprotocol/csharp-sdk#1868 · Opened Sep 11, 2026
Document ClientOAuthOptions.ScopeSelector usage Open

Difficulty 2/5 1-3 hours Newbie friendliness 78/100

modelcontextprotocol/csharp-sdk#1867 · Opened Sep 11, 2026
Support explicit OAuth authorization when MCP initialization succeeds anonymously Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/csharp-sdk#1866 · 1 comment · Opened Sep 10, 2026
Configure McpServerToolCreateOptions via WithTools Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 70/100

modelcontextprotocol/csharp-sdk#1865 · 1 reaction · Opened Sep 9, 2026
Add support for the Skills extension (SEP-2640) Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/csharp-sdk#1863 · Opened Sep 9, 2026
StreamableHttpClientSessionTransport loses a correlated JSON-RPC error in a chunked HTTP 200 response Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 72/100

modelcontextprotocol/csharp-sdk#1862 · 1 comment · Opened Sep 8, 2026
Stateful connection is intermittent. Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 52/100

modelcontextprotocol/csharp-sdk#1861 · Opened Sep 8, 2026
.net 9 targeting .net 10 packages Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

modelcontextprotocol/csharp-sdk#1859 · 2 comments · Opened Sep 7, 2026
ElicitAsync<T> throws where the untyped ElicitAsync succeeds under an outgoing-request interceptor Open

Difficulty 2/5 1-3 hours Newbie friendliness 35/100

modelcontextprotocol/csharp-sdk#1854 · Opened Sep 4, 2026
ProcessMessagesAsync's internal fire-and-forget task duplicates Completion's failure signal via TaskScheduler.UnobservedTaskException Open

Difficulty 3/5 1-2 days Newbie friendliness 70/100

modelcontextprotocol/csharp-sdk#1851 · 2 comments · Opened Sep 3, 2026
SDK Client: `ConnectAsync` discover→initialize fallback unreachable when `AutoDetect` transport fails with `HttpRequestException` Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 55/100

modelcontextprotocol/csharp-sdk#1848 · 1 comment · Opened Sep 1, 2026
Serialization exception when invoking a tool with an array parameter Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 58/100

modelcontextprotocol/csharp-sdk#1846 · 3 comments · Opened Aug 28, 2026
MCP Server is unstable when deployed to AWS AgentCore Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/csharp-sdk#1842 · Opened Aug 27, 2026
HTTP+SSE client: POST responses are never disposed, leaking one connection per sent message Open

Difficulty 1/5 Under an hour Newbie friendliness 88/100

modelcontextprotocol/csharp-sdk#1840 · 1 comment · Opened Aug 27, 2026
stdio client never closes the server's stdin, so every client dispose burns the full ShutdownTimeout (5s by default) Open

Difficulty 2/5 1-3 hours Newbie friendliness 84/100

modelcontextprotocol/csharp-sdk#1836 · Opened Aug 25, 2026
2.2.0: binary content blocks (ImageContentBlock, BlobResourceContents) serialize invalid base64 - client-side CallToolResult deserialization throws (regression of #1340) Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

modelcontextprotocol/csharp-sdk#1835 · 1 comment · Opened Aug 25, 2026
Interactive OAuth flow is aborted by DiscoverProbeTimeout during dual-path connect, then fails with an authorization state mismatch Open

area-auth bug P2

modelcontextprotocol/csharp-sdk#1830 · 2 comments · 1 assignee · Opened Aug 20, 2026
Add a stable server-side MCP Task execution extension point Open

enhancement P2 ready for work

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/csharp-sdk#1820 · 5 comments · Opened Aug 16, 2026
Support the OAuth 2.0 Device Authorization Grant (RFC 8628) for headless clients Open

area-auth enhancement

Difficulty 5/5 Over a week Newbie friendliness 45/100

modelcontextprotocol/csharp-sdk#1811 · 1 comment · Opened Aug 11, 2026
Flaky on windows-latest: OAuth metadata fetch times out in in-memory tests (same class as #1701, not covered by #1702) Open

area-tests bug help wanted P3 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 68/100

modelcontextprotocol/csharp-sdk#1806 · 3 comments · Opened Aug 9, 2026
Tool Call Failed: Request timed out Open

bug help wanted needs repro P3

Difficulty 4/5 3-5 days Newbie friendliness 38/100

modelcontextprotocol/csharp-sdk#1785 · 8 comments · Opened Aug 3, 2026
Streaming HTTP MCP server integration tests Open

documentation help wanted P3 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 42/100

modelcontextprotocol/csharp-sdk#1781 · 1 comment · Opened Aug 2, 2026
Wire up the three new auth conformance scenarios from Open

area-auth enhancement P3 ready for work

modelcontextprotocol/csharp-sdk#1770 · 2 comments · 1 assignee · Opened Jul 29, 2026
Bad Request of "Missing Session Id" from a stateful MCP server Open

needs repro

Difficulty 3/5 1-2 days Newbie friendliness 48/100

modelcontextprotocol/csharp-sdk#1759 · 3 comments · Opened Jul 28, 2026
Define handling for protocol-incompatible result properties set by applications Open

enhancement P2 ready for work

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/csharp-sdk#1754 · 1 comment · Opened Jul 27, 2026
Document the Windows `cmd.exe /c` interposition as a security-relevant property, not just a quoting bug Open

documentation enhancement P2 ready for work

modelcontextprotocol/csharp-sdk#1751 · 2 comments · 1 reaction · 1 assignee · Opened Jul 27, 2026
Provide extensions for calling McpClientTools as tasks Open

enhancement P3 ready for work

Difficulty 5/5 Over a week Newbie friendliness 38/100

modelcontextprotocol/csharp-sdk#1730 · 2 comments · Opened Jul 24, 2026
Deterministically cancel background task-store runners on server disposal via a server-lifetime CTS Open

bug enhancement P2 ready for work

modelcontextprotocol/csharp-sdk#1707 · 1 comment · 1 assignee · Opened Jul 16, 2026
Make server extension handlers composable with filters and subscriptions Open

enhancement P2 ready for work

modelcontextprotocol/csharp-sdk#1704 · 4 comments · 1 assignee · Opened Jul 14, 2026
Flaky test host hang on Windows Debug CI: TaskCancellationIntegrationTests.TaskTool_CancellationToken_GetTaskShowsWorkingBeforeCancel Open

area-tests bug P3 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/csharp-sdk#1701 · 2 comments · Opened Jul 13, 2026
Add prior-knowledge connection path for modern protocol clients Open

enhancement needs confirmation P2

Difficulty 4/5 3-5 days Newbie friendliness 45/100

modelcontextprotocol/csharp-sdk#1696 · Opened Jul 8, 2026
Optional exception summarization for server-side logging Open

enhancement P3 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 55/100

modelcontextprotocol/csharp-sdk#1690 · 4 comments · Opened Jul 6, 2026
Tool annotation default values are not applied Open

bug needs confirmation P3

Difficulty 3/5 1-2 days Newbie friendliness 48/100

modelcontextprotocol/csharp-sdk#1673 · 1 comment · Opened Jun 27, 2026
Conformance Track B: stateful HTTP/stdio modes, SEP-2549 absence-assert, remaining MRTR scenarios Open

area-tests enhancement P2

modelcontextprotocol/csharp-sdk#1653 · 1 assignee · Opened Jun 16, 2026
MCP Apps: Add [McpAppResource] attribute and resource-collection processing in WithMcpApps() Open

enhancement P3 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 58/100

modelcontextprotocol/csharp-sdk#1636 · 1 comment · Opened Jun 9, 2026
Restore `[McpServerTool]` composability with MRTR input requests + tasks Open

enhancement P2 ready for work

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/csharp-sdk#1635 · 1 comment · Opened Jun 8, 2026
Identity Assertion Grant uses raw authorization server URL as token-exchange audience Open

area-auth bug P2

modelcontextprotocol/csharp-sdk#1617 · 1 assignee · Opened Jun 1, 2026
Identity Assertion Grant flow only supports OIDC ID tokens, not SAML 2.0 assertions Open

area-auth enhancement P3 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 52/100

modelcontextprotocol/csharp-sdk#1618 · 1 comment · Opened Jun 1, 2026
Can't implement a CIMD client if auth provider doesn't put "none" first in it's list of supported token auth methods Open

area-auth bug P2

Difficulty 4/5 3-5 days Newbie friendliness 62/100

modelcontextprotocol/csharp-sdk#1612 · 1 comment · 1 reaction · Opened May 29, 2026
Cached-credential reuse via ClientOAuthOptions.ClientId fails: no way to specify token_endpoint_auth_method Open

area-auth enhancement P3 ready for work

modelcontextprotocol/csharp-sdk#1611 · 1 comment · 1 assignee · Opened May 29, 2026
MCP Apps: Add ergonomic WithAppTool helper to reduce wiring boilerplate Open

enhancement P3 ready for work

Difficulty 5/5 Over a week Newbie friendliness 45/100

modelcontextprotocol/csharp-sdk#1607 · 1 comment · Opened May 28, 2026
the context.RequestAborted not reliable in HandleSseRequestAsync Open

bug needs confirmation P3

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/csharp-sdk#1606 · Opened May 28, 2026
McpServerToolCreateOptions miss MarshalResult option. Open

enhancement P2 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 68/100

modelcontextprotocol/csharp-sdk#1602 · 2 comments · Opened May 26, 2026
StdioClientTransportOptions is failing with space in Command Open

bug P2 ready for work

modelcontextprotocol/csharp-sdk#1601 · 2 comments · 1 assignee · Opened May 25, 2026
OAuth token refresh fails with AADSTS9010010 Open

area-auth bug P2

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/csharp-sdk#1587 · Opened May 19, 2026
Option to support declarative tool registration activated by version (e.g. "beta") Open

enhancement P3 ready for work

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/csharp-sdk#1557 · 2 comments · Opened May 2, 2026
[Documentation request] Authentication architecture suggestions Open

documentation enhancement P3 ready for work

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/csharp-sdk#1494 · 3 comments · Opened Apr 2, 2026

modelcontextprotocol/csharp-sdk

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