[PR #5301] plugin/client: add mcp_stdio plugin #5235

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opened 2026-05-05 14:57:14 -06:00 by gitea-mirror · 0 comments

gitea-mirror commented

2026-05-05 14:57:14 -06:00

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📋 Pull Request Information

Original PR: https://github.com/fatedier/frp/pull/5301
Author: @ailenshen
Created: 4/29/2026
Status: 🔄 Open

Base: dev ← Head: feature/mcp-stdio-plugin

📝 Commits (3)

5822468 plugin/client: add mcp_stdio plugin
1f3d55a plugin/client: refactor mcp_stdio to use worker goroutine for child I/O
85e9150 plugin/client: address mcp_stdio review findings

📊 Changes

6 files changed (+665 additions, -1 deletions)

View changed files

📝 README.md (+1 -1)
📝 conf/frpc_full_example.toml (+16 -0)
📝 pkg/config/v1/proxy_plugin.go (+27 -0)
📝 pkg/config/v1/validation/plugin.go (+12 -0)
➕ pkg/plugin/client/mcp_stdio.go (+443 -0)
➕ pkg/plugin/client/mcp_stdio_test.go (+166 -0)

📄 Description

WHY

Most MCP (Model Context Protocol) servers in the wild ship as stdio
binaries — npx -y @org/mcp-..., uvx ... and similar — and only
know how to speak JSON-RPC over stdin/stdout. To make them reachable
by remote MCP clients like Claude Desktop or the Anthropic API today,
you have to run a separate stdio↔HTTP translator (e.g. mcp-proxy)
locally alongside frpc.

This PR adds an mcp_stdio client plugin that folds that translation
into frpc itself, so a single frpc process is enough to expose any
number of stdio MCP servers as remote Streamable HTTP endpoints — no
extra translator process and no new runtime dependencies.

What it does

Spawns the configured stdio command lazily on the first request.
For each inbound HTTP POST, writes the body as a JSON-RPC line to
the child's stdin and returns the next stdout line as the HTTP
response. Notifications (frames without an id) are accepted with
HTTP 202 and produce no stdio output.
Optional idleTimeoutSeconds: kill the child after N seconds of
inactivity. The MCP initialize handshake is cached and replayed
when the child is respawned, so sessions stay healthy across reaps
and the next spawn picks up any updated package version on its own
(useful with @latest style npx commands).

Configuration

```toml
proxies
name = "apple-notes"
type = "tcp"
remotePort = 3101
[proxies.plugin]
type = "mcp_stdio"
command = ["npx", "-y", "@modelcontextprotocol/server-everything"]
idleTimeoutSeconds = 300
```

Tested with

Real apple-notes and filesystem MCP servers end-to-end through a
public frps, reachable from Claude Desktop and claude.ai.
Unit tests cover JSON-RPC classification, dispatch, notifications,
and the respawn-with-replay path.
`golangci-lint run ./pkg/plugin/client/... ./pkg/config/v1/...`
passes.

_{🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.}

## 📋 Pull Request Information **Original PR:** https://github.com/fatedier/frp/pull/5301 **Author:** [@ailenshen](https://github.com/ailenshen) **Created:** 4/29/2026 **Status:** 🔄 Open **Base:** `dev` ← **Head:** `feature/mcp-stdio-plugin` --- ### 📝 Commits (3) - [`5822468`](https://github.com/fatedier/frp/commit/582246859df71ff097836cfcf2c5bb3cb662c67b) plugin/client: add mcp_stdio plugin - [`1f3d55a`](https://github.com/fatedier/frp/commit/1f3d55a012bec3e034aa8c5e2d9f4fde49f77cd5) plugin/client: refactor mcp_stdio to use worker goroutine for child I/O - [`85e9150`](https://github.com/fatedier/frp/commit/85e9150e62b4ad386d4a49d50d22005b0dd56788) plugin/client: address mcp_stdio review findings ### 📊 Changes **6 files changed** (+665 additions, -1 deletions) <details> <summary>View changed files</summary> 📝 `README.md` (+1 -1) 📝 `conf/frpc_full_example.toml` (+16 -0) 📝 `pkg/config/v1/proxy_plugin.go` (+27 -0) 📝 `pkg/config/v1/validation/plugin.go` (+12 -0) ➕ `pkg/plugin/client/mcp_stdio.go` (+443 -0) ➕ `pkg/plugin/client/mcp_stdio_test.go` (+166 -0) </details> ### 📄 Description ### WHY Most MCP (Model Context Protocol) servers in the wild ship as stdio binaries — `npx -y @org/mcp-...`, `uvx ...` and similar — and only know how to speak JSON-RPC over stdin/stdout. To make them reachable by remote MCP clients like Claude Desktop or the Anthropic API today, you have to run a separate stdio↔HTTP translator (e.g. `mcp-proxy`) locally alongside frpc. This PR adds an `mcp_stdio` client plugin that folds that translation into frpc itself, so a single frpc process is enough to expose any number of stdio MCP servers as remote Streamable HTTP endpoints — no extra translator process and no new runtime dependencies. ### What it does - Spawns the configured stdio command lazily on the first request. - For each inbound HTTP POST, writes the body as a JSON-RPC line to the child's stdin and returns the next stdout line as the HTTP response. Notifications (frames without an `id`) are accepted with HTTP 202 and produce no stdio output. - Optional `idleTimeoutSeconds`: kill the child after N seconds of inactivity. The MCP `initialize` handshake is cached and replayed when the child is respawned, so sessions stay healthy across reaps and the next spawn picks up any updated package version on its own (useful with `@latest` style npx commands). ### Configuration \`\`\`toml [[proxies]] name = "apple-notes" type = "tcp" remotePort = 3101 [proxies.plugin] type = "mcp_stdio" command = ["npx", "-y", "@modelcontextprotocol/server-everything"] idleTimeoutSeconds = 300 \`\`\` ### Tested with - Real apple-notes and filesystem MCP servers end-to-end through a public frps, reachable from Claude Desktop and claude.ai. - Unit tests cover JSON-RPC classification, dispatch, notifications, and the respawn-with-replay path. - \`golangci-lint run ./pkg/plugin/client/... ./pkg/config/v1/...\` passes. --- <sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>