ZEsarUX MCP Server

MCP server for ZEsarUX ZX Spectrum emulator using ZRCP protocol.

dtz-labs - Vibe coding 8-bit machines like there is no tomorrow

Features

13 tool categories with 50+ operations: machine control, PEEK/POKE, debugging (breakpoints, registers, disassembly), tape/disk loading, snapshots, keyboard input, assembly, and more.

Quick Start

Each client launches the server over stdio via npx — no clone or build needed. The server then connects to ZEsarUX on ZRCP port 10000, auto-launching it for you if nothing is listening there (on by default). Pick your client below; you'll still need ZEsarUX installed — see Installation.

Claude Code

Register the server with one command:

claude mcp add zesarux -- npx -y @dtz-labs/zesarux-mcp

Auto-launch is on by default. To disable it (only connect to a ZEsarUX you start yourself), set the env var:

claude mcp add zesarux --env ZESARUX_AUTOLAUNCH=false -- npx -y @dtz-labs/zesarux-mcp

Claude Desktop

Edit claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/claude_desktop_config.json; Windows: %APPDATA%\Claude\claude_desktop_config.json), then restart Claude Desktop:

{
  "mcpServers": {
    "zesarux": {
      "command": "npx",
      "args": ["-y", "@dtz-labs/zesarux-mcp"]
    }
  }
}

Codex

Add to ~/.codex/config.toml:

[mcp_servers.zesarux]
command = "npx"
args = ["-y", "@dtz-labs/zesarux-mcp"]

Opencode

Add to opencode.json (project) or ~/.config/opencode/opencode.json (global):

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "zesarux": {
      "type": "local",
      "command": ["npx", "-y", "@dtz-labs/zesarux-mcp"],
      "enabled": true
    }
  }
}

Installation

1. Install ZEsarUX

macOS:

brew install zesarux
xattr -dr com.apple.quarantine /Applications/zesarux.app

Why the second command? macOS Gatekeeper tags any app that wasn't downloaded through the App Store (or signed/notarized by an identified developer) with a com.apple.quarantine extended attribute. ZEsarUX isn't notarized, so the first time you launch it Gatekeeper refuses to open it ("can't be opened because Apple cannot check it for malicious software"). xattr -dr recursively strips that attribute from the app bundle, telling Gatekeeper to trust it. This is needed because the Homebrew cask drops the .app into /Applications but cannot clear the quarantine flag for you.

Linux:

sudo apt-get install zesarux

Or download from: ZEsarUX releases

For Windows, compiling from source, and enabling ZRCP via the config file, see the full Installation & Configuration guide.

2. Start ZEsarUX with ZRCP

zesarux --enable-remoteprotocol --remoteprotocol-port 10000

Or skip this step — the server auto-launches ZEsarUX for you by default (see Auto-launching ZEsarUX below).

3. Install the MCP Server

The server is published to npm as @dtz-labs/zesarux-mcp. Your MCP client launches it on demand via npx (see Quick Start), so nothing needs installing. To have it on your PATH as zesarux-mcp, install it globally:

npm install -g @dtz-labs/zesarux-mcp

<details> <summary>From source (for development)</summary>

git clone https://github.com/dtz-labs/zesarux-mcp.git
cd zesarux-mcp
npm install
npm run build   # produces dist/index.js

Then point your config at "command": "node", "args": ["/absolute/path/to/zesarux-mcp/dist/index.js"]. </details>

Environment variables

Variable	Default	Description
ZESARUX_HOST	localhost	Host where ZEsarUX ZRCP is listening
ZESARUX_PORT	(auto)	ZRCP port (matches --remoteprotocol-port). Unset in AUTO mode → first free port ≥ 10000; set it to pin a specific port
LOG_LEVEL	info	debug | info | warn | error (all logs go to stderr)
ZESARUX_TIMEOUT	30000	ZRCP request timeout, ms
ZESARUX_RETRY_ATTEMPTS	3	Connection retry attempts
ZESARUX_AUTO_RECONNECT	true	Reconnect automatically if the link drops
ZESARUX_AUTOLAUNCH	true	Start ZEsarUX automatically if it isn't reachable (set false to opt out)
ZESARUX_PATH	(auto-detected)	Explicit path to the ZEsarUX binary
ZESARUX_ARGS	(none)	Extra args appended when launching (e.g. --vo null --ao null for headless)
ZESARUX_LAUNCH_TIMEOUT	20000	How long to wait for the ZRCP port after launching, ms

Auto-launching ZEsarUX

By default, when ZEsarUX isn't reachable on startup the server finds a local ZEsarUX binary, launches it with --enable-remoteprotocol --remoteprotocol-port <port>, waits for the port, then connects. Set ZESARUX_AUTOLAUNCH=false to opt out (only connect to a ZEsarUX you started yourself). An emulator the server launched is terminated when the server stops; a ZEsarUX you started yourself is left untouched. See Installation & Configuration for binary discovery order and headless use.

You can also control the emulator process at runtime with the launch_emulator and kill_emulator tools (the latter only stops an emulator the server started). And if a tool call fails because the connection dropped, the server will — unless ZESARUX_AUTOLAUNCH=false — try once to relaunch ZEsarUX and reconnect before retrying the call.

Running several servers (automatic ports)

In AUTO mode (auto-launch on, ZESARUX_PORT not set) the server picks the first free port ≥ 10000 and launches its own ZEsarUX there. So you can register several MCP servers with no port configuration at all and they fan out automatically — the first takes 10000, the next 10001, then 10002, … each with its own emulator:

claude mcp add zesarux-a -- npx -y @dtz-labs/zesarux-mcp
claude mcp add zesarux-b -- npx -y @dtz-labs/zesarux-mcp

To pin a server to a specific port — or to attach to an emulator that is already running — set ZESARUX_PORT explicitly (e.g. ZESARUX_PORT=10000); the server then uses exactly that port and does not scan. Automatic port selection only happens in AUTO mode; with ZESARUX_AUTOLAUNCH=false the server just connects to ZESARUX_PORT (default 10000).

Documentation

• Documentation index - Start here
• Installation & Configuration - Install ZEsarUX and the server
• Configuring MCP Clients - Claude Desktop/Code, Codex, OpenCode, JetBrains
• Available Tools - All tools with examples
• Example Usage - Talk-to-it and quick call examples
• Development - Build, structure, protocol mapping
• Troubleshooting - Common problems
• ZRCP Specification - Complete protocol reference

Quick Examples

// Reset and set machine
{"name": "reset_machine"}
{"name": "set_machine", "arguments": {"machine": "128k"}}

// Read/write memory
{"name": "peek", "arguments": {"address": "4000", "length": 256}}
{"name": "poke", "arguments": {"address": "4000", "value": [255, 0]}}

// Debugging
{"name": "get_registers"}
{"name": "set_breakpoint", "arguments": {"index": 1, "type": "execute", "address": "8000"}}

// Load tape
{"name": "load_file", "arguments": {"filename": "/path/game.tap"}}

License

MIT

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