sysbridge MCPサーバー

Give your AI agent native filesystem, shell, and desktop control over any remote Linux PC, Cloud VPS, or Android Termux node without installing the agent on the target machine.

Why I Built This • Architecture • Quick Start • MCP Transports • Tool Catalog • Cryptographic Sudo • Go SDK

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📖 The Story: Why I Built sysbridge-mcp

I run my AI coding agent from an Android phone inside a Termux + Debian PRoot container while my actual workstation is an HP Pavilion G4 running a stripped-down Arch Linux + Sway Wayland setup (Daemon OS). My laptop has an old dual-core AMD A4-3330MX APU that lacks SSE4.2 and AES-NI instructions. Running modern bloated AI IDEs or heavy Node/Electron agent runtimes on that CPU causes immediate SIGILL core dumps or eats the RAM alive.

So the brain lived on my phone, and the muscle lived on my laptop.

At first, I did what every engineer does at 2 AM: I wrote a pile of bash scripts (ssh-laptop, ssh-phone) and a small UDP discovery daemon (buddy-link). Then I watched my AI agent try to edit files on the laptop over raw ssh user@host "cat << 'EOF' > file.go".

It was a comedy of errors:

1. The Backtick Massacre: Any file containing nested backticks, $variables, or escaped quotes got mangled by two layers of shell expansion before hitting disk.
2. The Wi-Fi Roam Curse: Whenever I unplugged USB tethering and switched to mobile hotspot, the laptop's IP changed, the TCP pipe snapped, and my 20-minute kernel build died at 94%.
3. The Termux FUSE Wall: You cannot run sshfs inside an unprivileged Android PRoot container because /dev/fuse is locked down.
4. The Sudo Dilemma: I wanted my agent to manage systemd services and mount LUKS vaults on my laptop, but I refused to put plaintext sudo passwords in a prompt or set %wheel ALL=(ALL) NOPASSWD: ALL so anyone touching my physical keyboard had root.

I realized I did not want an "SSH wrapper." I wanted my agent to treat a remote laptop, a $4/month cloud VPS, or a homelab server as if its filesystem and process table were local, with zero software required on the remote machine by default, and optional superpowers when both machines run the binary.

That is why I merged buddy-link and my Arch workstation tooling into sysbridge-mcp.

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⚡ What Makes sysbridge-mcp Different

• Zero-Install Remote Default (Mode A): Point it at any fresh Ubuntu, Debian, Arch, macOS, or Alpine VPS running standard sshd. Nothing needs to be installed on the remote host. No root required on either side.
• Mountless 3-Tier Virtual Filesystem (pkg/vfs): Works on Android Termux, Docker containers, macOS, and Linux without kernel FUSE (sshfs). Surgical file reads, atomic writes, multi-hunk edits, and directory trees run over an in-memory Go SFTP subsystem (sftp-vfs) multiplexed over a warm SSH pool, with automatic fallback to POSIX byte streams (ssh-stream) if SFTP is disabled.
• Broken-Pipe Immunity: Commands that run longer than 5s (configurable) automatically detach into a remote tmux session (or nohup + PID sentinel if tmux is not installed on the target VPS). Your Wi-Fi can drop for ten minutes while the remote compilation finishes undisturbed.
• 7-Stage Zero-Hunt IP Resolver: Never type ip addr or arp -a again. Resolves dynamic peers across UDP :42424 HMAC-SHA256 beacons, Linux AF_NETLINK instant link-state bursts, USB tethering (rndis0/usb0/ncm0), hotspot ARP/ADB neighbor MAC tables, and local subnet probes in <1ms.
• Cryptographic Passwordless Sudo (pam_ssh_agent_auth): Keep sudo disabled by default, or enable sudo.mode: "agent_forward" to forward your SSH agent socket per request. The remote PAM stack verifies a cryptographic signature from your SSH key, granting the agent root access without ever exposing a password or weakening physical console sudo.
• Hardware Blocklist Guardrails: Hard-block specific block devices (such as /dev/sda on dual-boot machines) and critical paths (/boot/efi) inside the Go engine before any command or file write leaves the process.

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🏗️ System Architecture

How the 3-Tier VFS & Progressive Peer Engine Works

Layer	Primary Driver	Automatic Fallback	Root Required?	Target Requirement
Filesystem (fs_*)	sftp-vfs (Multiplexed Go SFTP over SSH pool)	ssh-stream (Atomic temp-file POSIX byte streams)	No	Standard sshd
Command Runner (exec_run)	Warm SSH channel + tmux auto-detach (>5s)	nohup + PID & exit-code sentinel in /tmp	No	Standard /bin/sh
Port Tunnels (tunnel_manage)	Native Go net.Listener <-> ssh.Client channel copy	Auto-rebind supervisor on peer IP change	No	AllowTcpForwarding yes
Peer Discovery (peer_*)	Static IP / DNS / ~/.ssh/config host	7-Stage Cascade + UDP :42424 HMAC-SHA256 Mesh	No	Optional sysbridge-mcp daemon
Privilege Elevation (sudo)	Disabled by default (sudo.mode: "disabled")	agent_forward via pam_ssh_agent_auth.so	Opt-In	pam_ssh_agent_auth

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🚀 Quick Start

1. One-Line Install (Linux, macOS, Android Termux)

curl -fsSL https://raw.githubusercontent.com/0xOpCode/sysbridge-mcp/main/install.sh | sh

2. Install via Go Toolchain

go install github.com/0xOpCode/sysbridge-mcp/cmd/sysbridge-mcp@latest

3. Build from Source

git clone https://github.com/0xOpCode/sysbridge-mcp.git
cd sysbridge-mcp
CGO_ENABLED=0 go build -ldflags="-s -w" -o sysbridge-mcp ./cmd/sysbridge-mcp

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🎯 Complete User Setup Guide: 3 Progressive Tiers

You can use sysbridge-mcp in three progressive tiers depending on how much control you want over the remote machine.

Tier 1: Zero-Install SSH Mode (Any Cloud VPS, Linux PC, or macOS Host)

Best for: Production VPS servers, cloud VMs, or shared machines where you do not want to install extra software or use sudo.

• Target Machine Requirements: Standard sshd and your SSH public key in ~/.ssh/authorized_keys. Nothing is installed on the remote machine.
• Controller Setup (~/.config/sysbridge/config.yaml):

  default_peer: "my_vps"
  peers:
    my_vps:
      name: "my_vps"
      host: "203.0.113.42"          # IP or domain name
      user: "ubuntu"                # Normal non-root user
      ssh_port: 22
      auth:
        method: "key"
        identity_file: "~/.ssh/id_ed25519"
      sudo:
        mode: "disabled"            # Strictly non-sudo
      vfs:
        backend: "auto"             # Uses sftp-vfs, falls back to ssh-stream
        workspace_root: "/home/ubuntu/projects"
  

• Or register dynamically from chat without touching config: Ask your agent: "Connect to peer my_vps at 203.0.113.42 with user ubuntu and save config." (peer_connect tool).
• What you get immediately: Full fs_read, fs_write, fs_edit, fs_multi_edit, fs_search, fs_ops, exec_run (with automatic nohup backgrounding for commands >5s), and native Go SSH port tunnels (tunnel_manage).

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Tier 2: Unbreakable Roaming Workstation (tmux + mosh + rg + rsync)

Best for: Heavy compilation, kernel/Docker builds, and coding over mobile hotspots or unstable Wi-Fi.

1. Ask your agent to audit the remote machine:

   Run peer_provision with action="audit" on peer "laptop"
   

2. Install the standard packages on the target machine if missing:
   • Arch Linux: sudo pacman -S tmux mosh ripgrep rsync
   • Ubuntu / Debian: sudo apt install tmux mosh ripgrep rsync
   • macOS: brew install tmux mosh ripgrep rsync

• What this unlocks:
  • Commands running longer than 5s detach into named tmux sessions (/tmp/sysbridge_<id>.log) that you can inspect, tail, or send keystrokes to via task_control.
  • mosh_control spawns mosh-server over UDP 60000:61000 so interactive terminal sessions survive IP changes and laptop sleep.
  • fs_search accelerates content search using rg (ripgrep), and sync_transfer uses delta rsync.

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Tier 3: Full P2P Mesh (<1ms Zero-IP-Hunt) + Cryptographic Agent Sudo

Best for: Phone (Termux) <-> Laptop / Homelab setups where IPs change constantly across Wi-Fi, Hotspot, and USB Tethering.

Step A: Enable Bidirectional UDP :42424 Mesh Discovery (Rootless)

1. Generate a shared 256-bit HMAC key on Machine A:

   mkdir -p ~/.config/sysbridge && chmod 700 ~/.config/sysbridge
   sysbridge-mcp keygen > ~/.config/sysbridge/secret.key
   chmod 600 ~/.config/sysbridge/secret.key
   

2. Copy the same ~/.config/sysbridge/secret.key to Machine B and install sysbridge-mcp on Machine B (curl -fsSL https://raw.githubusercontent.com/0xOpCode/sysbridge-mcp/main/install.sh | sh).
3. Ask the agent to enable the rootless user-level mesh service on Machine B:

   Run peer_provision with action="setup_user_mesh" and apply=true on peer "laptop"
   

   (This creates and starts ~/.config/systemd/user/sysbridge-mesh.service running sysbridge-mcp daemon --port 42424 without root).
4. Set host: "auto" in your peer config. Both machines now discover each other's live IP in <1ms via signed UDP beacons and Linux Netlink interface bursts.

Step B: Optional Cryptographic Passwordless Sudo (pam_ssh_agent_auth)

If you want your agent to run sudo commands on the remote workstation when connected with your SSH key, without setting NOPASSWD: ALL for local console users:

1. Ask the agent to generate or apply the PAM configuration:

   Run peer_provision with action="setup_pam_ssh_sudo" on peer "laptop"
   

2. Ensure /etc and /etc/security are owned by root:root with mode 0755 (pam_ssh_agent_auth.so rejects authentication if /etc is group-writable 0775), your public key is in /etc/security/authorized_keys, and sudo.mode: "agent_forward" is set in config.yaml.

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🔌 Multi-Protocol MCP Transports

sysbridge-mcp implements every MCP transport protocol in a single static binary:

# 1. Standard I/O (Default - Claude Code, Claude Desktop, Cursor, Windsurf, Zed)
sysbridge-mcp --transport stdio

# 2. Streamable HTTP (Single /mcp endpoint with session management)
sysbridge-mcp --transport http --listen 127.0.0.1:8787

# 3. Legacy SSE (/sse stream + /message POST for n8n and older MCP gateways)
sysbridge-mcp --transport sse --listen 127.0.0.1:8787

# 4. Dual HTTP Mode (Serves both /mcp Streamable HTTP, /sse + /message, and /healthz on one port)
sysbridge-mcp --transport dual --listen 0.0.0.0:8787

# 5. Unix Domain Socket (Share one warm SSH/SFTP pool across multiple local CLI sessions)
sysbridge-mcp --transport unix --socket ~/.cache/sysbridge/sysbridge.sock

Client Configuration Snippets

claude mcp add sysbridge -- sysbridge-mcp --transport stdio

{
  "mcpServers": {
    "sysbridge": {
      "command": "sysbridge-mcp",
      "args": ["--transport", "stdio", "--config", "~/.config/sysbridge/config.yaml"]
    }
  }
}

Start the server in dual mode with a Bearer token:

export SYSBRIDGE_TOKEN="your-secret-token"
sysbridge-mcp --transport dual --listen 0.0.0.0:8787

Connect n8n's MCP Client node to http://your-host:8787/sse or Streamable HTTP clients to http://your-host:8787/mcp with header Authorization: Bearer your-secret-token.

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🛠️ MCP Tool Catalog (14 Unified Tools)

Instead of exposing 50 granular shell wrappers that bloat the model's context window, sysbridge-mcp provides 14 high-density tools that work identically across local mounts, SFTP, and raw SSH streams:

Tool Name	Category	Description
peer_list	Mesh & Peers	List configured and discovered peers, IP resolution stage, active VFS backend (sftp-vfs / ssh-stream), and RTT latency.
peer_connect	Mesh & Peers	Probe connectivity, switch the active default peer, or register a new SSH/VPS host at runtime without restarting.
peer_provision	Mesh & Peers	Audit remote capabilities or opt-in provision rootless systemd --user mesh beacons and pam_ssh_agent_auth sudo rules.
fs_read	Virtual FS	Read remote files with line numbers, offset/limit pagination, or base64 encoding for binary/image assets.
fs_write	Virtual FS	Atomic remote file write via temp-file + fsync + POSIX rename while preserving file mode bits.
fs_edit	Virtual FS	Surgical exact-block replacement (old_string -> new_string, single or replace_all) returning a unified diff.
fs_multi_edit	Virtual FS	Apply multiple sequential surgical edits to a remote file in one atomic SFTP/stream transaction.
fs_search	Virtual FS	Fast remote file pattern matching (glob) and content regex search (grep via rg/grep or SFTP walk).
fs_ops	Virtual FS	Unified filesystem operations: ls, tree, stat, mkdir, mv, cp, chmod, rm (with confirmation guard), and sha256.
exec_run	Compute & Shell	Run commands over warm SSH channels with custom cwd, env, sudo, and automatic >5s detachment into tmux or nohup.
task_control	Compute & Shell	Inspect or control detached background jobs: list, status, tail, send_keys, and kill.
mosh_control	Roaming UDP	Spawn mosh-server on the remote host, verify UDP port reachability (60000:61000), and return MOSH_KEY session details.
tunnel_manage	Networking	Create, list, and remove persistent or RAM-only local (-L) and reverse (-R) port tunnels in pure Go.
sync_transfer	File Sync	SFTP push/pull transfers, one-shot rsync delta directory sync, and live background directory watchers.
sys_bridge	OS & Desktop	Single-call hardware/OS telemetry, systemctl service control, Wayland (swaymsg/grim) & Android (adb) screen capture, clipboard sync, and alerts.

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🔐 Cryptographic Sudo Bridge (pam_ssh_agent_auth)

By default, every peer starts with sudo.mode: "disabled". The agent runs strictly inside the non-root SSH user's permissions.

If you want your agent to perform system administration on your workstation or VPS without putting a sudo password in config files and without setting NOPASSWD: ALL in /etc/sudoers:

1. Enable pam_ssh_agent_auth on the remote Linux host (you can ask the agent to run peer_provision with action: "setup_pam_ssh_sudo" to generate or apply the exact config):

   # /etc/sudoers.d/sysbridge-agent
   Defaults env_keep += "SSH_AUTH_SOCK"
   
   # /etc/pam.d/sudo (top line)
   auth sufficient pam_ssh_agent_auth.so file=/etc/security/authorized_keys
   

2. Set sudo.mode: "agent_forward" for that peer in ~/.config/sysbridge/config.yaml.
3. When a tool call passes sudo: true, sysbridge-mcp attaches your local SSH_AUTH_SOCK agent channel to that SSH session. sudo verifies a cryptographic signature from your SSH private key. Anyone typing sudo on the physical laptop keyboard still has to type the normal password.

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📦 Using as a Go Library

All core engines live in importable pkg/* packages so you can embed sysbridge-mcp into your own Go agents or orchestrators:

package main

import (
	"context"
	"fmt"

	"github.com/0xOpCode/sysbridge-mcp/internal/config"
	"github.com/0xOpCode/sysbridge-mcp/pkg/safety"
	"github.com/0xOpCode/sysbridge-mcp/pkg/transport"
	"github.com/0xOpCode/sysbridge-mcp/pkg/vfs"
)

func main() {
	cfg := config.DefaultConfig()
	guard := safety.NewGuard(cfg.Safety.BlockedDevices, cfg.Safety.BlockedPaths, true)
	pool := transport.NewPool(cfg, guard, nil)
	defer pool.Close()

	fsEngine := vfs.NewEngine(pool)
	res, err := fsEngine.ReadFile(context.Background(), "laptop", "/etc/hostname", 1, 10)
	if err != nil {
		panic(err)
	}
	fmt.Printf("Read via %s: %s\n", res.Backend, res.Content)
}

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🧭 Standalone CLI Subcommands

Alongside running as an MCP server, sysbridge-mcp includes direct CLI subcommands that replace legacy buddy-link and ssh-laptop scripts:

sysbridge-mcp serve [--transport stdio|http|sse|dual|unix] [--listen :8787]
sysbridge-mcp daemon [--port 42424]          # Run background UDP P2P mesh discovery & tunnel supervisor
sysbridge-mcp status [peer]                  # Show peer link status, IP, VFS tier, and telemetry
sysbridge-mcp ip [peer]                      # Output raw resolved peer IP for shell scripts
sysbridge-mcp exec [-d] [-peer name] <cmd>   # Run command on peer (auto-detaches in tmux/nohup with -d)
sysbridge-mcp send [-peer name] <file>       # Push file via SFTP/SCP to peer Downloads directory
sysbridge-mcp tunnel <add|list|remove>       # Manage persistent and RAM-only SSH port tunnels
sysbridge-mcp keygen                         # Generate a new 256-bit hex HMAC mesh secret key
sysbridge-mcp version                        # Print version and build metadata

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📄 License

Released under the MIT License. Built by Akash Deep (@0xOpCode).