✨ Winx - MCP Server for Shell & Coding Agents ✨

🦀 Native Rust implementation inspired by WCGW, built for local code-agent workflows

A local MCP server you can hand to a coding agent and stop worrying about the shell.

Winx is the MCP server I wanted while running Claude, Codex, and friends against real repos: one process that handles the shell, file IO, and PTY-backed interactive sessions, written in Rust so it doesn't fight you on stdio.

It started as a Rust port of WCGW but isn't a Python wrapper. Everything runs on a real PTY (via portable-pty), cd actually sticks, Ctrl+C actually interrupts, and background shells survive long-running TUIs without leaking output buffers into your token budget.

What you get

• A stateful bash session per thread with proper PTY semantics — foreground, background, status checks, text input, Enter/Ctrl-C/Ctrl-D, raw ASCII. Multiline scripts and top-level command shorthand both work; NUL bytes are rejected before they reach the shell.
• Workspaces with three modes: wcgw (full access), architect (read-only), code_writer (allowlist of commands and write globs). The command allowlist is parsed with tree-sitter, so it checks every command on the line — pipelines, &&/||/;, command substitution, subshells — not just the first word, and can't be bypassed with ls && curl … | sh or ls $(rm …).
• A resilient PTY: a shell that won't return to a prompt (even after Ctrl-C) is auto-reset at the same cwd/mode, child processes are reaped on drop, and prompt detection is robust to a custom PS1. Opt into zsh with WINX_SHELL=zsh.
• File reads with WCGW-style line ranges (file.rs:10-40, file.rs:10-, file.rs:-40). Active files are tracked and prioritized in the repository context across calls.
• File writes and SEARCH/REPLACE edits that survive ambiguous matches, indentation drift, and the usual unicode quote-mismatches from LLMs. Writes are blocked when the file hasn't been read or the cached content is stale.
• ContextSave for handing a task summary plus its files to the next session — including workspace context, active files, git status/diff, and terminal sharing for proper resumption. Resuming reopens the saved project root and token-caps the restored memory so it never overflows the context window.
• ReadImage so multimodal clients can pull screenshots, mockups, error PNGs, etc.
• Clean, token-aware shell output: cursor/ANSI noise from interactive programs (REPLs, progress bars) is rendered away through a terminal emulator, and mechanical repetition is collapsed losslessly (line [winx: ×N]) so build/install logs don't blow your context budget. Toggle the collapsing with WINX_NO_COMPRESS.
• Two transports: stdio for local clients, plus an optional token-gated Streamable HTTP server (winx serve --http) for remote MCP clients like ChatGPT — see Remote access.

MCP Tools

Tool	What it does
Initialize	Boots the workspace, picks the mode, hands you a thread_id. Call this first or everything else errors out. With no workspace path it spins up a scratch playground; resuming a task (task_id_to_resume) reopens its saved project root.
BashCommand	Runs commands, polls long-running ones, sends Enter/Ctrl-C, drives TUIs. Supports is_background, status_check, send_text, send_specials, send_ascii, allow_multi for multi-statement scripts.
ReadFiles	One or many files, with line numbers. Append :10-40 to a path for a range. When the token budget is hit it tells you the exact line + file:N-M syntax to resume from instead of silently dropping the tail.
FileWriteOrEdit	Full overwrites or SEARCH/REPLACE blocks. Validates file read coverage and freshness before writing, then runs a tree-sitter syntax check (18+ languages) and points at the offending line with a snippet.
ContextSave	Dumps task description + file globs into a single text file with workspace context, active files, and git status/diff for clean handoff and task resumption.
ReadImage	Returns a native MCP image content block (not base64 as text), so multimodal models actually see the image.

Search/Replace editing

Standard block syntax:

<<<<<<< SEARCH
old content
=======
new content
>>>>>>> REPLACE

Things the matcher forgives so you don't have to babysit the model:

• atomic: ambiguous or missing matches abort without touching the file
• adjusts replacement indentation when the LLM gets the leading whitespace wrong
• strips ReadFiles line numbers if they leak into a SEARCH block
• normalizes the usual "smart quote" / em-dash / ellipsis substitutions
• uses neighboring blocks to disambiguate when the same snippet appears twice
• single-line substring edits work — you don't need the whole line in SEARCH
• retries once with \" unescaped when the model over-escapes quotes in SEARCH
• refuses edits that only matched after too much fuzzy fixup, and rejects blocks that match in too many places — so you re-read instead of corrupting the file

Install

cargo install winx-code-agent

Binary lands in ~/.cargo/bin — every config snippet below assumes that's on $PATH. If your MCP client launches with a sterile env, swap winx-code-agent for the absolute path (which winx-code-agent).

Needs Rust 1.75+, Linux/macOS/WSL2, and a real terminal (any modern one — Winx spawns its own PTY).

Claude Code (CLI)

One-liner via the CLI (stdio is the default transport):

claude mcp add winx -- winx-code-agent

Or drop a .mcp.json in your project root:

{
  "mcpServers": {
    "winx": {
      "command": "winx-code-agent",
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

Claude Desktop

Add to your config file (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows):

{
  "mcpServers": {
    "winx": {
      "command": "winx-code-agent",
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

Restart Claude Desktop after saving.

Codex (OpenAI CLI)

One-liner:

codex mcp add winx -- winx-code-agent

Or edit ~/.codex/config.toml:

[mcp_servers.winx]
command = "winx-code-agent"
env = { RUST_LOG = "winx_code_agent=info" }

Cursor

Add to ~/.cursor/mcp.json (or .cursor/mcp.json for project-local):

{
  "mcpServers": {
    "winx": {
      "command": "winx-code-agent",
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

VS Code (Copilot Chat / MCP)

Add to .vscode/mcp.json:

{
  "servers": {
    "winx": {
      "type": "stdio",
      "command": "winx-code-agent"
    }
  }
}

Zed

Add to your Zed settings (~/.config/zed/settings.json):

{
  "context_servers": {
    "winx": {
      "source": "custom",
      "command": "winx-code-agent",
      "args": [],
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

Windsurf

Add to ~/.codeium/windsurf/mcp_config.json:

{
  "mcpServers": {
    "winx": {
      "command": "winx-code-agent",
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

OpenCode

Add to opencode.json:

{
  "mcp": {
    "winx": {
      "type": "local",
      "command": ["winx-code-agent"],
      "enabled": true,
      "environment": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

Gemini CLI

Add to ~/.gemini/settings.json:

{
  "mcpServers": {
    "winx": {
      "command": "winx-code-agent",
      "args": [],
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

agy (Google Antigravity CLI)

agy is Google's new Gemini-powered CLI (Go binary, usually at ~/.local/bin/agy). No mcp add subcommand yet — it reads MCP servers from JSON.

Edit ~/.gemini/config/mcp_config.json (also ~/.gemini/antigravity/mcp_config.json if you run the Antigravity IDE alongside):

{
  "mcpServers": {
    "winx": {
      "command": "winx-code-agent",
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

If winx-code-agent is not on the agy process $PATH, swap command for the absolute path (~/.cargo/bin/winx-code-agent after cargo install winx-code-agent).

Continue.dev

Add to your ~/.continue/config.yaml:

mcpServers:
  - name: winx
    command: winx-code-agent
    env:
      RUST_LOG: winx_code_agent=info

Kiro

Add to ~/.kiro/settings/mcp.json:

{
  "mcpServers": {
    "winx": {
      "command": "winx-code-agent",
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

Warp

Settings → MCP Servers → Add MCP Server:

{
  "winx": {
    "command": "winx-code-agent",
    "env": { "RUST_LOG": "winx_code_agent=info" }
  }
}

Roo Code

Add to your Roo Code MCP config:

{
  "mcpServers": {
    "winx": {
      "type": "stdio",
      "command": "winx-code-agent"
    }
  }
}

Other clients (generic stdio)

Any client that speaks stdio MCP works with this shape:

{
  "mcpServers": {
    "winx": {
      "command": "winx-code-agent",
      "args": [],
      "env": { "RUST_LOG": "winx_code_agent=info" }
    }
  }
}

If your client launches Winx with an empty $PATH, swap command for the absolute path ( ~/.cargo/bin/winx-code-agent).

Build from source

For unreleased changes or a custom build:

git clone https://github.com/gabrielmaialva33/winx-code-agent.git
cd winx-code-agent
cargo install --path .

Or run it without installing:

cargo run --release

Check it's wired up

List MCP tools in your client. You should see six entries: Initialize, BashCommand, ReadFiles, FileWriteOrEdit, ContextSave, ReadImage. The first call always has to be Initialize — Winx tracks workspace + mode per thread.

Remote access (ChatGPT & other remote MCP clients)

By default Winx speaks MCP over stdio — the local transport every desktop client (Claude Desktop, Cursor, VS Code) uses. For clients that live in the cloud and can't reach your machine over stdio — like ChatGPT's developer-mode custom connectors — Winx can also serve MCP over Streamable HTTP:

winx serve --http --bind 127.0.0.1:8000 --token "$(openssl rand -hex 24)"

The MCP protocol is served at /mcp. Every request must carry the token, either as Authorization: Bearer <token> or a ?token=<token> query parameter. Without a token the server refuses to start — serving a shell over the network without auth is remote code execution waiting to happen.

Flag	Purpose
--http	Serve over Streamable HTTP instead of stdio.
--bind	Listen address. Defaults to 127.0.0.1:8000. Keep it on loopback.
--token	Shared secret required on every request. Falls back to the WINX_HTTP_TOKEN env var.
--allowed-host	Extra Host authority to accept (your tunnel hostname). Repeatable. Loopback is always allowed.

Remote clients run in the cloud, so the endpoint has to be reachable over HTTPS — put a tunnel in front of the loopback listener and allow its hostname through the built-in DNS-rebinding guard:

# 1. tunnel first, to learn the public hostname
cloudflared tunnel --url http://localhost:8000
#    -> https://<random>.trycloudflare.com

# 2. start Winx, allowing that host
winx serve --http --bind 127.0.0.1:8000 \
     --token "$(openssl rand -hex 24)" \
     --allowed-host <random>.trycloudflare.com

In ChatGPT (Settings → Apps → Advanced → Developer mode), add a connector with:

• URL: https://<random>.trycloudflare.com/mcp?token=<your-token>
• Authentication: None (the secret rides in the URL)

Remote clients are effectively stateless — they don't reuse the MCP session between tool calls — so the HTTP transport shares one shell session across all requests: the shell Initialize creates stays alive for the lifetime of the server, and later BashCommand calls find it. Reuse the same thread_id across calls.

Warning

The HTTP transport puts arbitrary shell and file access on the network. Anyone with the token (and URL) gets a shell on your machine as your user — and not just inside the workspace, since BashCommand in wcgw mode isn't path-restricted. Bind to loopback, keep it behind an authenticated tunnel, prefer architect/code_writer mode or a container, and shut it down when you're done.

Environment variables

All optional — Winx works out of the box without any of these.

Variable	Effect
RUST_LOG	Log verbosity, e.g. winx_code_agent=info. At info you get the per-call audit trail (tool name, arg summary, duration, ok/error).
WINX_HTTP_TOKEN	Shared secret for the HTTP transport, used if --token isn't passed (see Remote access).
WINX_NO_COMPRESS	Set to 1 to disable output compression and see raw, uncollapsed shell output (the [winx: ×N] collapsing is on by default).
WINX_KEEP_TAIL_PIPE	Set to 1 to keep a trailing | tail … instead of stripping it. Winx truncates output server-side, so by default it drops a redundant trailing tail (wcgw parity).
WINX_USE_SCREEN / WINX_ATTACH_TERMINAL	Run the shell inside screen/tmux so you can attach to the live session. Set to screen, tmux, or any truthy value; Winx prints an attach hint on Initialize.
WINX_OPEN_CONTEXT	Set to 1 to open the saved context file in your default app after ContextSave.
WINX_SHELL	Set to zsh to run the session under zsh instead of bash (opt-in; bash stays the default). Falls back to bash if zsh isn't on PATH or the mode is restricted.
WINX_SERVER_INSTRUCTIONS	Extra operator instructions appended to every Initialize response (e.g. house rules for the agent).

Hacking on it

cargo fmt --all
cargo clippy --all-targets --all-features -- -D warnings
cargo test --all-features

CI runs the same three. If you touch src/state/pty.rs or anything in src/tools/bash_command.rs, the regression suite at tests/bash_pty_regression_test.rs is what protects against the usual TUI/PTY foot-guns — run it first.

A note on security

By default this is a local (stdio) MCP server. Anything connected to it can read files, edit files, and run shell commands inside the workspace — same blast radius as letting the model into your terminal. The optional HTTP transport (--http) extends that reach to the network; see Remote access for the extra precautions it demands.

If you want a tighter leash:

• architect mode disables writes and most commands;
• code_writer mode lets you allowlist commands and write globs.

SECURITY.md has the disclosure process and threat model.

License

MIT - Gabriel Maia (@gabrielmaialva33)