pty-mcp

pty-mcp

[pty-mcp MCP server]

An MCP (Model Context Protocol) server that gives AI agents interactive terminal sessions — local shells, SSH, serial ports, and persistent remote sessions that survive disconnects.

Built for sysadmins and network engineers who want AI to help with real server and device management, not just code generation.

[AI agent interacting with Telehack BBS via pty-mcp]

Why

AI agents run commands in non-interactive shells. They can't:

• SSH into a server and interact with running processes
• Connect to routers or switches via serial console
• Monitor logs and react when a specific event occurs
• Keep session state across multiple commands
• Wait for a server to reboot and detect when it's back up

pty-mcp solves all of these by providing real PTY sessions over MCP.

Without pty-mcp, AI agents resort to sleep 30 && check_status loops — burning CPU cycles and API calls waiting for things to happen. With wait_for, the agent blocks server-side until the event occurs. Less polling, less energy, better for polar bears. 🐻‍❄️

Use Cases

Server administration

# Reboot a server and wait until it's back onlinecreate_local_session("ping myserver")read_output(wait_for: "bytes from", timeout: 300)→ blocks until server responds after reboot (~80s, one tool call)

Network device management

# Connect to a router via serial consolecreate_serial_session(port: "/dev/ttyUSB0", baud: 9600)send_input("show interfaces status")read_output(wait_for: "\\$")

Log monitoring and alerting

# Watch logs and act when something happenscreate_ssh_session(host: "prod", user: "admin")send_input("tail -f /var/log/app.log")read_output(wait_for: "ERROR|CRITICAL", timeout: 3600)→ returns the error line + context when it appears

Long-running tasks that survive disconnects

create_ssh_session(host: "server", user: "admin", persistent: true)send_input("apt upgrade -y")detach_session()          → close Claude Code, task continues# Reconnect later to check result

Features

Architecture

┌─────────────────────────────────────────────────────┐│ AI Agent (Claude Code, etc.)                        ││                                                     ││  MCP Tools: create_local_session, send_input,       ││             send_control, read_output, close_session │└──────────────────────┬──────────────────────────────┘                       │ JSON-RPC stdio┌──────────────────────┴──────────────────────────────┐│ pty-mcp (MCP Server)                                ││                                                     ││  Session Manager                                    ││  ├── LocalSession  (local PTY via creack/pty)       ││  ├── SSHSession    (remote PTY via x/crypto/ssh)    ││  ├── SerialSession (serial port via go.bug.st)      ││  └── RemoteSession (persistent via ai-tmux)         │└─────────────────────────────────────────────────────┘
Persistent mode (ai-tmux):
  pty-mcp ──SSH──▶ ai-tmux client ──Unix socket──▶ ai-tmux server (daemon)                                                     ├── PTY: bash                                                     ├── PTY: ssh admin@router                                                     └── PTY: tail -f /var/log/syslog

Quick Start

Claude Code Plugin (recommended)

Installs the binary automatically and registers the MCP server:

claude plugin marketplace add raychao-oao/pty-mcpclaude plugin install pty-mcp@pty-mcp

Restart Claude Code — the binary downloads automatically on session start, then restart once more to activate it. No manual claude mcp add needed.

Updating:

claude plugin marketplace update pty-mcpclaude plugin update pty-mcp@pty-mcp

Restart Claude Code — the new binary downloads automatically on session start, then restart once more to apply the update.

Manual install

One-line install + register (macOS / Linux / WSL2):

curl -fsSL https://raw.githubusercontent.com/raychao-oao/pty-mcp/main/install.sh | shclaude mcp add pty-mcp -- /usr/local/bin/pty-mcp

Restart Claude Code and the tools are available.

chmod +x pty-mcp-*sudo mv pty-mcp-* /usr/local/bin/pty-mcpclaude mcp add pty-mcp -- /usr/local/bin/pty-mcp

go install github.com/raychao-oao/pty-mcp@latestclaude mcp add pty-mcp -- $(go env GOPATH)/bin/pty-mcp

WSL2 Notes

pty-mcp works in WSL2 out of the box. Use the Linux binary:

# Inside WSL2curl -fsSL https://raw.githubusercontent.com/raychao-oao/pty-mcp/main/install.sh | shclaude mcp add pty-mcp -- /usr/local/bin/pty-mcp

Optional: Install ai-tmux on remote servers

For persistent sessions that survive SSH disconnects, install ai-tmux on your remote server:

# Download for your server's architecturecurl -fsSL https://raw.githubusercontent.com/raychao-oao/pty-mcp/main/install.sh | sh# Or just copy the binary:scp /usr/local/bin/ai-tmux your-server:/usr/local/bin/ai-tmux

Usage Examples

Once registered, the AI agent can use these MCP tools:

Local interactive shell:

create_local_session()                    → {session_id, type: "local"}send_input(session_id, "cd /tmp && ls")   → {output: "...", is_complete: true}send_input(session_id, "python3")         → start Python REPLsend_input(session_id, "print('hello')")  → {output: "hello\n>>>"}send_control(session_id, "ctrl+d")        → exit Pythonclose_session(session_id)

SSH to remote server:

create_ssh_session(host: "myserver", user: "admin")send_input(session_id, "top")send_control(session_id, "ctrl+c")        → stop top

Wait for pattern (v0.2.0):

create_local_session("ping myserver")read_output(session_id, wait_for: "bytes from", timeout: 300)→ blocks until server responds or 5 min timeout
send_input(session_id, "docker-compose up")read_output(session_id, wait_for: "ready|error", timeout: 60, context_lines: 3)→ returns matched line + 3 lines of context

Send secret / password (v0.3.0):

# AI detects a password prompt, calls send_secret instead of handling the password itselfcreate_ssh_session(host: "router", user: "admin")read_output(session_id, wait_for: "Password:")   → session is waiting for input
send_secret(session_id, prompt: "Router admin password:")→ native GUI dialog appears on the operator's screen (macOS: system dialog,   WSL2: Windows Get-Credential, Linux: zenity/kdialog)→ operator types password — it is sent directly to the PTY session→ AI only sees: {success: true, length: 12}→ password never appears in AI context or logs

Persistent session (survives SSH disconnect):

create_ssh_session(host: "server", user: "admin", persistent: true)send_input(session_id, "make build")      → start long builddetach_session(session_id)                → disconnect, build continues
# Later (even after restart):list_remote_sessions(host: "server", user: "admin")  → see running sessionscreate_ssh_session(host: "server", user: "admin", session_id: "abc123")  → reattachsend_input(session_id, "echo $?")         → check build result

MCP Tools

¹ send_secret platform support: macOS uses a native password dialog (osascript). WSL2 uses powershell.exe Get-Credential (Windows GUI dialog). Linux with a display server uses zenity or kdialog. Headless Linux falls back to /dev/tty. On macOS/Linux, if the operator doesn't respond within 60 seconds, the dialog is dismissed and the call returns a timeout error instead of falling through to another dialog or waiting again; cancelling the call (e.g. pressing ESC in Claude Code) dismisses the dialog immediately the same way. WSL2 is the exception: its dialog has no timeout and is never force-closed, including on cancellation — killing a WSL-interop-launched process that owns an open Windows GUI window was found to freeze the hosting terminal (unresponsive to input, scrolling, and selection) until the operator closes that terminal, with no way to recover it short of that. The dialog just waits until the operator answers or clicks Cancel themselves, which exits normally.

Audit Log

pty-mcp includes an optional audit log feature that records every send_input command to a central collector. This lets teams review and trace what AI agents did during a session.

Important: This is a voluntary, self-reporting operation log. It relies on operators choosing to enable it and run the collector. Because pty-mcp runs on the operator's own machine, there is no technical mechanism to enforce logging — a non-compliant operator could simply run pty-mcp without audit enabled. This feature provides traceability for teams that want it, but it is not a substitute for system-level audit tools (e.g., auditd, syslog forwarding, SSH session recording) in environments where audit compliance is required.

What it records

• Timestamp, operator identity, session ID, session type (local/ssh/serial), target host
• The exact input sent via send_input (including raw=true inputs like menu selections)
• Output snippet (first 2 KB) after each command
• A cmd_id linking the command to its output

send_secret is never logged — secrets entered via the GUI dialog do not appear in the audit log.

Commands and output snippets are automatically redacted before being written. The following patterns are replaced with [REDACTED] or [PRIVATE KEY REDACTED]:

• Key-value credentials: password=, passwd:, token=, api_key=, access_key=, auth_token=, secret=
• HTTP Authorization headers: Authorization: Bearer …, Authorization: Basic …, Authorization: Token …
• PEM private key blocks: -----BEGIN RSA PRIVATE KEY----- / -----BEGIN OPENSSH PRIVATE KEY-----

Setup

Each operator runs once to create their config and generate a token:

pty-mcp audit init

This creates ~/.config/pty-mcp/config (chmod 600) with a randomly generated token and prints the token to share with the collector admin.

The collector admin starts the server (using the token from init output):

PTY_MCP_AUDIT_TOKEN=<token-from-init> \  pty-mcp audit serve --port 9099 --log /var/log/pty-mcp-audit.jsonl

Enable audit after setting the collector URL in the config:

# Edit config and set: audit-url=http://your-collector:9099pty-mcp audit enable# Restart Claude Code to apply

To temporarily stop logging without losing your config:

pty-mcp audit disable

Operators without a config file are unaffected — audit is off by default.

Audit modes

Reviewing logs

Logs are stored as JSONL (one JSON object per line), readable with standard tools:

# All commands by operator raygrep '"user":"ray"' /var/log/pty-mcp-audit.jsonl | jq .
# Commands sent to a specific hostjq 'select(.target == "root@prod01")' /var/log/pty-mcp-audit.jsonl

ai-tmux: Persistent Terminal Daemon

ai-tmux is a lightweight daemon that runs on remote servers, keeping PTY sessions alive across SSH disconnects. Think of it as tmux designed for AI agents.

Install on remote server

# Cross-compile for LinuxGOOS=linux GOARCH=amd64 go build -o ai-tmux-linux ./cmd/ai-tmux/
# Copy to serverscp ai-tmux-linux server:~/ai-tmuxssh server "chmod +x ~/ai-tmux && sudo mv ~/ai-tmux /usr/local/bin/ai-tmux"

How it works

• ai-tmux server — daemon mode, listens on Unix socket, manages PTY sessions
• ai-tmux client — bridge mode, forwards JSON protocol over stdin/stdout (used by pty-mcp over SSH)
• ai-tmux list — list active sessions

The daemon auto-starts when pty-mcp connects with persistent: true. Sessions are reaped after 30 minutes of inactivity.

pty-mcp checks ai-tmux --version on the remote host before opening a session and returns a clear error if the binary is missing or below the minimum required version — no cryptic connection errors.

SSH Config Support

pty-mcp reads ~/.ssh/config to resolve host aliases:

# ~/.ssh/configHost myserver    HostName 192.168.1.100    User admin    Port 2222    IdentityFile ~/.ssh/id_ed25519

create_ssh_session(host: "myserver", user: "admin")# Automatically resolves hostname, port, and identity file

Requirements

• Go 1.25+
• For serial: appropriate device permissions
• For persistent sessions: ai-tmux binary on remote server

Changelog

See CHANGELOG.md for version history.

License

MIT