MCP 2026-07-28 client: streamable-HTTP and stdio transports, MRTR, subscriptions and the tasks extension.

mcp

model-context-protocol

client

async

moon add marianoguerra/mcp-client@0.7.0

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Author

marianoguerra

Version

0.7.0

License

MIT

Repository

github.com/marianoguerra/mcp-mb

Last updated

2 days ago

Downloads

Dependencies

marianoguerra/mcp0.7.0
moonbitlang/async0.20.3

README

#marianoguerra/mcp-client

A Model Context Protocol 2026-07-28 client: transports, the request engine, MRTR, subscriptions and the tasks extension.

moon add marianoguerra/mcp-client

Native only, because moonbitlang/async's process spawning and HTTP client are. If you need another backend, depend on marianoguerra/mcp and implement its Transport trait yourself.

#What is in it

Package	Purpose
@client	server/discover, the request engine and its MRTR retry loop, subscriptions/listen, and the io.modelcontextprotocol/tasks extension
@transport_http	Streamable HTTP: POST-only, SEP-2243 headers, request-scoped SSE streams
@transport_stdio	A child process speaking newline-delimited JSON-RPC
@sse	SSE framing over an @io.Reader

#Notes on the era

There is no initialize handshake, no session id, no GET stream. server/discover replaces all of it, and a 2025-era server will answer it with -32601.
Server-to-client requests are gone. A server that needs input returns an input_required result and the client retries the original request with a new id (MRTR, SEP-2322). What the client can answer depends on the capabilities it declares.
resources/subscribe, ping and logging/setLevel were removed. Push notifications come from one long-lived subscriptions/listen POST; the log level is a per-request _meta opt-in.
A task-augmented tools/call returns a seed with resultType: "task" — the request is finished, the work is not — and progress comes from polling tasks/get.

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