Tier 2 Application: cxxmcp (C++ SDK)
Repository: https://github.com/caomengxuan666/cxxmcp
Maintainer: @caomengxuan666 (sole maintainer)
Language: C++17
Current version: v1.1.1
Summary
cxxmcp is a community-driven C++ SDK implementing the full MCP specification, including the 2026 draft. It provides both server and client transports (Streamable HTTP, SSE, stdio), OAuth 2.1 authorization, and comprehensive conformance coverage.
Conformance Results
All results from local modelcontextprotocol/conformance --suite all:
| Target |
Result |
| Server latest (all) |
109 passed, 1 failed (99%) |
| Client latest (all, OpenSSL) |
447 passed, 0 failed (100%) |
Server 2025-11-25 (all) |
47 passed, 0 failed |
Client 2025-11-25 (all) |
224 passed, 1 failed |
| Client auth suite |
217 passed, 0 failed |
Known Exception
The single server failure (http-header-validation / ServerRejectsMissingMethodHeader) is an upstream issue in the TypeScript SDK conformance client — it does not send the required Mcp-Method header per SEP-2243. The cxxmcp client correctly sends this header. Tracked at:
Once PR #2178 is merged, cxxmcp can enable strict SEP-2243 validation to reach 110/110 (100%).
Comparison with RMCP (official Rust SDK)
Using identical --suite all runs on the same machine:
| Target |
cxxmcp |
RMCP |
| Server latest (all) |
109 passed, 1 failed |
48 passed, 47 failed |
| Client latest (all) |
447 passed, 0 failed |
runner crashed (empty/non-JSON response) |
Tier-Check Automated Assessment
npx @modelcontextprotocol/conformance tier-check --repo caomengxuan666/cxxmcp --skip-conformance
| Check |
Status |
Detail |
| Labels |
pass |
12/12 required labels |
| Triage |
pass |
100% within 2BD, median 0h, p95 0h |
| P0 Resolution |
pass |
0 open, 0/0 closed within 7d |
| Stable Release |
pass |
v1.1.1 (stable) |
| Policy Signals |
partial |
Missing: .github/dependabot.yml, renovate.json |
| Spec Tracking |
fail |
184d gap (SDK release lagged behind 2025-11-25 spec) |
Evidence Links
Note on Tier Selection
While cxxmcp's conformance scores meet Tier 1 thresholds (99% server, 100% client), applying for Tier 2 given:
- Sole maintainer — cannot commit to Tier 2's full maintenance SLA without additional contributors
- C++ is a niche language in the MCP ecosystem
- spec_tracking gap due to delayed first release after 2025-11-25 spec
The conformance evidence and tier-check results are available for community review.
Tier 2 Application: cxxmcp (C++ SDK)
Repository: https://github.com/caomengxuan666/cxxmcp
Maintainer: @caomengxuan666 (sole maintainer)
Language: C++17
Current version: v1.1.1
Summary
cxxmcp is a community-driven C++ SDK implementing the full MCP specification, including the 2026 draft. It provides both server and client transports (Streamable HTTP, SSE, stdio), OAuth 2.1 authorization, and comprehensive conformance coverage.
Conformance Results
All results from local
modelcontextprotocol/conformance --suite all:2025-11-25(all)2025-11-25(all)Known Exception
The single server failure (
http-header-validation / ServerRejectsMissingMethodHeader) is an upstream issue in the TypeScript SDK conformance client — it does not send the requiredMcp-Methodheader per SEP-2243. The cxxmcp client correctly sends this header. Tracked at:Once PR #2178 is merged, cxxmcp can enable strict SEP-2243 validation to reach 110/110 (100%).
Comparison with RMCP (official Rust SDK)
Using identical
--suite allruns on the same machine:Tier-Check Automated Assessment
Evidence Links
cxxmcp-examples/CONFORMANCE_STATUS.mdNote on Tier Selection
While cxxmcp's conformance scores meet Tier 1 thresholds (99% server, 100% client), applying for Tier 2 given:
The conformance evidence and tier-check results are available for community review.