Cxxmcp

cxxmcp

[](https://isocpp.org/) [](https://cmake.org/) [](https://github.com/caomengxuan666/cxxmcp/actions/workflows/release-gates.yml) [](https://caomengxuan666.github.io/cxxmcp/) [](LICENSE) [](https://modelcontextprotocol.io/) [-brightgreen.svg)](docs/conformanceevidence.md) [-brightgreen.svg)](docs/conformanceevidence.md)

A production-ready C++17 SDK for the Model Context Protocol — build MCP servers and clients that embed directly into native C++ applications, with full protocol coverage and cross-SDK conformance validation.

Read this in [Chinese](README_zh.md).

Quick Start

find_package(cxxmcp CONFIG REQUIRED)
target_link_libraries(my_server PRIVATE cxxmcp::server)
target_link_libraries(my_client PRIVATE cxxmcp::client)

#include 
#include 

int main() {
    return mcp::ServerPeer::builder()
        .name("demo-server")
        .version("1.0.0")
        .stdio()
        .tool("echo",
            [](const mcp::protocol::Json& input) {
                return mcp::protocol::Json{{"echo", input}};
            })
        .run();
}

// Client side
#include 
#include 

int main() {
    int status = 0;
    const auto run_status = mcp::ClientPeer::builder()
        .streamable_http("http://127.0.0.1:3000/mcp")
        .run([&status](auto& svc) {
            if (!svc.peer().initialize().has_value() ||
                !svc.peer().notify_initialized().has_value() ||
                !svc.peer().list_all_tools().has_value() ||
                !svc.peer()
                     .call_tool("echo",
                                mcp::protocol::Json{{"value", "hello"}})
                     .has_value()) {
                status = 1;
            }
        });
    return run_status == 0 ? status : run_status;
}

What It Covers

| Area | Status | |---|---| | Protocol & JSON-RPC | Typed models, serialization, initialize validation, raw escape hatches | | Server SDK | Tool/prompt/resource registries, typed handlers, task-aware calls, notifications | | Client SDK | HTTP, stdio, process-stdio, async helpers, roots, sampling, elicitation, tasks | | Transports | stdio, process stdio, Streamable HTTP (stateful sessions), legacy SSE compat, WebSocket (auto-reconnect) | | Packaging | CMake find_package, Conan 2, vcpkg overlay, FetchContent / CPM | | Peer/Service boundary | RMCP-style role-aware Peer and Service |

Protocol coverage: tool, prompt, resource, resource template, completion, logging, roots, sampling, elicitation, task lifecycle, progress, cancellation, and raw JSON-RPC escape hatches for vendor extensions.

Conformance: Validated against the official modelcontextprotocol/conformance runner (--suite all).

| | cxxmcp | RMCP | |---|---|---| | Server | 109/110 (99%) | 48/95 (51%) | | Client | 448/448 (100%) | — (runner crashed) |

Full details in [conformance evidence](docs/conformance_evidence.md).

Capability Snapshot

cxxmcp is a release-candidate-quality C++ MCP SDK with full protocol coverage, cross-SDK conformance validation, and multiple transport options. See [conformance evidence](docs/conformanceevidence.md) and [ecosystem maturity evidence](docs/ecosystemmaturity_evidence.md) for details.

Install

find_package(cxxmcp CONFIG REQUIRED)

# Server
target_link_libraries(my_server PRIVATE cxxmcp::server)
# Client
target_link_libraries(my_client PRIVATE cxxmcp::client)
# Everything
target_link_libraries(my_app PRIVATE cxxmcp::sdk)

Build from source:

cmake -S . -B build -DCXXMCP_BUILD_CLIENT=ON -DCXXMCP_BUILD_SERVER=ON
cmake --build build --config Release
cmake --install build --config Release --prefix out/install/cxxmcp

The quick-start client uses Streamable HTTP, so source builds that compile that client path must also set -DCXXMCP_ENABLE_HTTP=ON.

Package managers: conanfile.py (Conan 2), packaging/vcpkg/ports/cxxmcp-sdk (vcpkg overlay), packaging/xmake/ (xmake). See [package consumption](docs/package_consumption.md).

CMake Options

| Option | Default | Description | |---|---:|---| | CXXMCP_BUILD_SDK | ON | Build the aggregate SDK layer (protocol + client + server) | | CXXMCP_BUILD_CLIENT | OFF | Build the MCP client library | | CXXMCP_BUILD_SERVER | OFF | Build the MCP server library | | CXXMCP_BUILD_EXAMPLES | OFF | Build example executables | | CXXMCP_BUILD_TESTS | BUILD_TESTING | Build tests | | CXXMCP_BUILD_BENCHMARKS | OFF | Build benchmark executables | | CXXMCP_ENABLE_HTTP | OFF | Build HTTP/SSE transport (uses bundled cpp-httplib unless CXXMCP_USE_SYSTEM_DEPS=ON) | | CXXMCP_ENABLE_OPENSSL | OFF | Enable OpenSSL-backed HTTP/WebSocket TLS support | | CXXMCP_ENABLE_AUTH | OFF | Build the optional OAuth 2.1 / DPoP auth target | | CXXMCP_ENABLE_WEBSOCKET | OFF | Build WebSocket transport (requires CXXMCP_ENABLE_HTTP) |

Package Targets

| Target | Purpose | |---|---| | cxxmcp::protocol | MCP protocol models and JSON-RPC serialization | | cxxmcp::transport | Role-generic transport contracts | | cxxmcp::handler | Client/server handler interfaces | | cxxmcp::peer | Role-aware execution boundary | | cxxmcp::service | Service lifecycle boundary | | cxxmcp::client | Embeddable MCP client SDK | | cxxmcp::server | Embeddable MCP server SDK | | cxxmcp::auth | Optional OAuth 2.1 / DPoP contract (CXXMCP_ENABLE_AUTH=ON) | | cxxmcp::auth_openssl | Optional OpenSSL-backed JOSE/JWT/DPoP helpers (CXXMCP_ENABLE_AUTH=ON, CXXMCP_AUTH_CRYPTO=OpenSSL) | | cxxmcp::sdk | Aggregate public SDK target |

Why cxxmcp

• Standard CMake SDK consumption — find_package and go
• C++17 public API, no runtime dependencies beyond the standard library
• Full MCP protocol coverage with typed, capability-gated helpers
• Cross-SDK conformance validation against the official runner
• RMCP-style Peer/Service architecture designed for embedding
• stdio, process-stdio, Streamable HTTP, and WebSocket transports out of the box

Examples

In-tree examples cover server/client peers, auth, tasks, elicitation, and transport adapters. Run them with:

cmake --preset examples && cmake --build --preset examples && ctest --preset examples

See [examples.md](docs/examples.md) for the full list. The separate cxxmcp-examples repository exercises the SDK through an external CMake project with advanced scenarios.

Documentation

• GitHub Pages — API reference
• [Conformance evidence](docs/conformance_evidence.md) — test results and known exceptions
• [Compatibility policy](docs/compatibility_policy.md) — versioning, compiler matrix, ABI
• [Dependency policy](DEPENDENCY_POLICY.md) — update policy and package dependency boundaries
• [HTTP transport backend evidence](docs/compatibility_policy.md#http-transport-backend-evidence)
• [Release gates](docs/release_gates.md) — release-blocking checks
• [Runtime gateway](docs/runtime_gateway.md) — external gateway boundary
• [Examples](docs/examples.md) — full example list
• [Auth design](docs/auth_design.md) — OAuth 2.1 / DPoP direction
• [Request lifecycle](docs/request_lifecycle.md) — timeout, cancellation, progress, shutdown
• [Contributing](CONTRIBUTING.md) | [Security](SECURITY.md) | [Changelog](CHANGELOG.md)

Status

cxxmcp is a community C++ MCP SDK preparing official SDK candidate evidence. The Peer/Service boundary, transport layer, and conformance gates are in release-candidate shape. It is not an official MCP SDK unless accepted by the MCP maintainers.

Compiler Compatibility

MinGW UCRT64 GCC and MinGW CLANG64 Clang are tracked as provisional, best-effort compiler compatibility evidence. These targets are not release-supported. The compiler-compat workflow runs them with continue-on-error: true while they remain provisional.

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: caomengxuan666
• Source: caomengxuan666/cxxmcp
• License: MIT

Install and usage instructions live in the source repository linked above.