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Filename	Latest commit message	Latest commit date
Will Pfleger ee1c63c53f feat(transport): add Unix domain socket client for streamable HTTP (#749 ) * feat(transport): add Unix domain socket client for streamable HTTP MCP hosts in Kubernetes environments with Envoy sidecars need to route HTTP through Unix domain sockets because DNS-based URIs only resolve via the proxy. Adds UnixSocketHttpClient implementing StreamableHttpClient using hyper over tokio::net::UnixStream, gated behind the transport-streamable-http-client-unix-socket feature. Also extracts RESERVED_HEADERS, extract_scope_from_header, and validate_custom_header into common/http_header.rs to share header validation logic between the reqwest and unix socket implementations. * fix(transport): address review feedback for unix socket transport - Document one-connection-per-request behavior on UnixSocketHttpClient - Reject empty socket paths and bare '@' in constructor with assert - Add explicit dep:http to unix-socket feature for self-documenting deps - Document MCP-Protocol-Version exception on RESERVED_HEADERS constant - Fix test catch-all to echo request id instead of hardcoding 1 - Remove leftover sleep(100ms) in test_unix_socket_custom_headers - Add blank line before macro comment in Cargo.toml * fix(transport): fix CI failures for unix socket transport - Use std::io::Error::other() instead of Error::new(ErrorKind::Other) to satisfy clippy::io_other_error on newer nightly - Use #[tokio::test(flavor = "current_thread")] for unix socket tests since axum's serve(UnixListener) requires spawn_local - Gate validate_custom_header behind client-side-sse feature since it references http::HeaderName which isn't available with default features * fix(transport): fix CI failures for unix socket transport axum::serve(UnixListener) uses spawn_local on Linux, which panics outside a LocalSet. Replace with manual hyper HTTP/1.1 server that accepts connections directly from the UnixListener, avoiding the spawn_local requirement entirely. * fix(transport): skip unix socket tests when local feature is enabled The local feature causes ().serve(transport) to use spawn_local, which requires a LocalSet. Gate the integration tests with not(feature = "local") to match every other integration test in the repo.		2026-03-24 09:50:32 -04:00
..
src	feat(transport): add Unix domain socket client for streamable HTTP (#749 )	2026-03-24 09:50:32 -04:00
tests	feat(transport): add Unix domain socket client for streamable HTTP (#749 )	2026-03-24 09:50:32 -04:00
build.rs	chore: add pre-commit hook for conventional commit verification (#619 )	2026-01-14 16:01:28 -05:00
Cargo.toml	feat(transport): add Unix domain socket client for streamable HTTP (#749 )	2026-03-24 09:50:32 -04:00
CHANGELOG.md	chore: release v1.2.0 (#736 )	2026-03-11 10:28:11 -04:00
README.md	feat: add local feature for !Send tool handler support (#740 )	2026-03-11 17:22:56 -04:00

README.md

rmcp

The official Rust SDK for the Model Context Protocol. Build MCP servers that expose tools, resources, and prompts to AI assistants — or build clients that connect to them.

For getting started, usage guides, and full MCP feature documentation (resources, prompts, sampling, roots, logging, completions, subscriptions, etc.), see the main README.

Feature Flags

Feature	Description	Default
`server`	Server functionality and the tool system	✅
`client`	Client functionality
`macros`	`#[tool]` / `#[prompt]` macros (re-exports `rmcp-macros`)	✅
`schemars`	JSON Schema generation for tool definitions
`auth`	OAuth 2.0 authentication support
`elicitation`	Elicitation support

Transport features

Feature	Description
`transport-io`	Server-side stdio transport
`transport-child-process`	Client-side stdio transport (spawns a child process)
`transport-async-rw`	Generic async read/write transport
`transport-streamable-http-client`	Streamable HTTP client (transport-agnostic)
`transport-streamable-http-client-reqwest`	Streamable HTTP client with default `reqwest` backend
`transport-streamable-http-server`	Streamable HTTP server transport

TLS backend options (for HTTP transports)

Feature	Description
`reqwest`	Uses rustls — pure Rust TLS (recommended default)
`reqwest-native-tls`	Uses platform-native TLS (OpenSSL / Secure Transport / SChannel)
`reqwest-tls-no-provider`	Uses rustls without a default crypto provider (bring your own)

Transports

The transport layer is pluggable. Two built-in pairs cover the most common cases:

	Client	Server
stdio	`TokioChildProcess`	`stdio`
Streamable HTTP	`StreamableHttpClientTransport`	`StreamableHttpService`

Any type that implements the Transport trait can be used. The IntoTransport helper trait provides automatic conversions from:

(Sink, Stream) or a combined Sink + Stream
(AsyncRead, AsyncWrite) or a combined AsyncRead + AsyncWrite
A Worker implementation
A Transport implementation directly

License

This project is licensed under the terms specified in the repository's LICENSE file.