Unofficial C++ SDK for MCP released, passes official conformance suite

Developers released mcp-cpp, a C++17 SDK for the MCP protocol, which is absent from the ten official language SDKs. It passed the official conformance suite: 42/42 server checks and 399/399 client checks for the 2026-07-28 spec.

• mcp-cpp is a C++17 SDK with no async runtime, one bundled JSON header and an optional HTTP library
• Server passed 42/42 checks and 20/20 scenarios of the official conformance suite
• Client passed 32/32 scenarios and 399/399 checks, including all 25 OAuth 2.1 scenarios
• Testing uncovered five real bugs, including dropped notifications over HTTP transport