2026-07-28 Spec Compliance

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SEP-2164: Standardize resource not found error code (-32602)

Status: Closed (completed).

#1540 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on May 26, 2026

SEP-1865: MCP Apps - Interactive User Interfaces for MCP

enhancementNew feature or requestNew feature or request

P2Moderate issues, valuable feature requestsModerate issues, valuable feature requests

ready for workHas enough information to startHas enough information to start

Status: Closed (completed).

#1431 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 17, 2026

SEP-2243: HTTP Standardization

Status: Closed (completed).

#1541 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on May 14, 2026

SEP-837: Update authorization spec to clarify client type requirements

area-auth

P0Critical: core functionality failures or high-severity securityCritical: core functionality failures or high-severity security

Status: Closed (completed).

Enhancement

#1545 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jul 22, 2026

SEP-2322: Multi Round-Trip Requests

Status: Closed (completed).

#1546 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 3, 2026

SEP-2350: Clarify client-side scope accumulation in step-up authorization

area-auth

Status: Closed (completed).

#1547 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 22, 2026

SEP-2567: Sessionless MCP via Explicit State Handles

Status: Closed (completed).

Enhancement

#1548 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 24, 2026

SEP-2575: Make MCP Stateless

Status: Closed (completed).

Enhancement

#1549 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 24, 2026

SEP-2106: Tools inputSchema/outputSchema conform to JSON Schema 2020-12

Status: Closed (completed).

#1550 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 16, 2026

SEP-2468: Recommend Issuer (iss) Parameter in MCP Auth Responses

area-auth

Status: Closed (completed).

Enhancement

#1571 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jul 23, 2026

SEP-2549: TTL for List Results

Status: Closed (completed).

#1572 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 15, 2026

SEP-2663: Tasks Extension

Status: Closed (completed).

#1573 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 11, 2026

SEP-2577: Deprecate Roots, Sampling, and Logging

Status: Closed (completed).

Enhancement

#1588 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jun 23, 2026

SEP-2260: Require Server requests to be associated with a Client request

Status: Closed (completed).

#1589 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on May 28, 2026

SEP-414: Document OpenTelemetry Trace Context Propagation Conventions

Status: Closed (completed).

#1630 In modelcontextprotocol/csharp-sdk;

· by localden was closed on Jun 8, 2026

SEP-2133: Extensions framework for MCP

Status: Closed (completed).

#1631 In modelcontextprotocol/csharp-sdk;

· by localden was closed on Jun 8, 2026

SEP-2207: OIDC-flavored refresh token guidance

Status: Closed (completed).

#1632 In modelcontextprotocol/csharp-sdk;

· by localden was closed on Jun 8, 2026

SEP-2351: Explicitly specify RFC 8414 well-known URI suffix for MCP

Status: Closed (completed).

#1633 In modelcontextprotocol/csharp-sdk;

· by localden was closed on Jun 8, 2026

SEP-2352: Clarify authorization server binding and migration

area-auth

Status: Closed (completed).

#1634 In modelcontextprotocol/csharp-sdk;

· by localden was closed on Jun 8, 2026

Implement SEP-2663 Tasks Extension

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1579

#1579 In modelcontextprotocol/csharp-sdk;

· by PranavSenthilnathan was closed on Jun 11, 2026

Add SEP-2549 caching hints (ttlMs and cacheScope) to cacheable results

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1623

#1623 In modelcontextprotocol/csharp-sdk;

· by tarekgh was closed on Jun 15, 2026

Implement RFC 9207 issuer validation in ClientOAuthProvider

area-auth

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

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1605

#1605 In modelcontextprotocol/csharp-sdk;

· by mikekistler was closed on Jul 23, 2026

Relax outputSchema to any JSON Schema 2020-12 document per SEP-2106

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

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1568

#1568 In modelcontextprotocol/csharp-sdk;

· by jayaraman-venkatesan was closed on Jun 16, 2026

Default draft protocol support: sessionless + handshake-less (SEP-2575 + SEP-2567)

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

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1610

#1610 In modelcontextprotocol/csharp-sdk;

· by halter73 was closed on Jun 24, 2026

Add MCP Apps extension support (typed metadata, attribute, and helpers)

Status: Merged (completed).

modelcontextprotocol/csharp-sdknumber 1484

#1484 In modelcontextprotocol/csharp-sdk;

· by Copilot was closed on Jun 17, 2026