ssh-mcp

# @yawlabs/ssh-mcp

[![npm version](https://img.shields.io/npm/v/@yawlabs/ssh-mcp)](https://www.npmjs.com/package/@yawlabs/ssh-mcp)
[![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)

**Make SSH work for AI tools.** MCP server that manages your SSH environment, diagnoses what's broken, fixes it, and gives your agent remote access to anything.

Built and maintained by [Yaw Labs](https://yaw.sh).

[![Add to Yaw MCP](https://yaw.sh/yaw-mcp-button.svg)](https://yaw.sh/mcp/install?name=SSH&command=npx&args=-y%2C%40yawlabs%2Fssh-mcp&description=Run%20commands%20on%20remote%20hosts%2C%20transfer%20files%2C%20manage%20SSH%20tunnels%20and%20keys&source=https%3A%2F%2Fgithub.com%2FYawLabs%2Fssh-mcp)

One click adds this to your local Yaw MCP config so it's available in every Yaw Terminal session. Or install manually below.

## The problem

AI CLI tools run in subprocesses where SSH is constantly broken. The agent tries to `git pull` and gets `Permission denied (publickey)`. It tries to SSH into a server and the agent socket is stale. It tries to deploy and the host key changed because the instance was recreated. Every time, the AI has no idea what's wrong and spirals.

This happens across every situation that needs SSH keys:

- **Git** — clone, pull, push, fetch, submodules, LFS
- **Package managers** — `npm install`, `pip install`, `go get`, `cargo`, `composer` from private repos
- **Server access** — SSH, SCP, SFTP, rsync
- **Tunneling** — port forwarding to databases, SOCKS proxies
- **Deployment** — Ansible, Terraform, Capistrano, deploy scripts
- **Cloud** — AWS EC2, GCP, Azure, DigitalOcean, any VPS

**ssh-mcp** fixes this. It manages the SSH agent, loads keys, diagnoses failures with actionable fix commands, and provides remote operations — all as MCP tools your AI agent can call.

## Quick start

Add to your MCP client config:

```json
{
  "mcpServers": {
    "ssh": {
      "command": "npx",
      "args": ["-y", "@yawlabs/ssh-mcp@latest"]
    }
  }
}
```

On Windows wrap with `cmd /c` since Node 20+ can't spawn `.cmd` files directly:

```json
{
  "mcpServers": {
    "ssh": {
      "command": "cmd",
      "args": ["/c", "npx", "-y", "@yawlabs/ssh-mcp@latest"]
    }
  }
}
```

The `@latest` tag makes `npx` re-resolve against the registry on every spawn, so each MCP session uses the newest published version. Or install globally if you'd rather pin (no auto-update):

```bash
npm install -g @yawlabs/ssh-mcp
# then in client config: "command": "ssh-mcp"
```

## Tools

### SSH environment management

Tools that fix your local SSH setup so everything else — git, deploys, tunnels — stops breaking.

| Tool | Description |
|------|-------------|
| `ssh_agent_ensure` | Ensure ssh-agent is running. Starts one if needed and sets env vars for the session. |
| `ssh_key_list` | List all SSH keys in ~/.ssh/ with type, fingerprint, and agent status. |
| `ssh_key_load` | Load a key into the running agent. Ensures the agent is started first. |
| `ssh_config_lookup` | Resolve the effective SSH config for a host (hostname, user, port, proxy, identity files). |
| `ssh_known_hosts_fix` | Remove a stale host key and re-scan. Fixes "host key verification failed" errors. |
| `ssh_git_check` | Test Git-over-SSH auth to GitHub, GitLab, Bitbucket, etc. |
| `ssh_test` | Quick connectivity test with timing and actionable error details. |

### Diagnostics

| Tool | Description |
|------|-------------|
| `ssh_diagnose` | Full SSH environment diagnostic. Checks agent, keys, config, known_hosts, and connectivity. Returns exact fix commands for every failure. |

### Remote operations

| Tool | Description |
|------|-------------|
| `ssh_exec` | Execute a command on a remote host. Returns stdout, stderr, and exit code (or `[signal: NAME]` and `code: -1` when the channel closed signal-only). Optional `env` param sets per-call environment variables (POSIX-safe prefix, works regardless of sshd's `AcceptEnv`). Subject to [command policy](#command-policy) if configured. |
| `ssh_read_file` | Read a file from a remote host via SFTP. |
| `ssh_write_file` | Write content to a file on a remote host via SFTP. |
| `ssh_upload` | Upload a local file to a remote host via SFTP. |
| `ssh_download` | Download a file from a remote host to local filesystem. |
| `ssh_ls` | List files in a directory on a remote host. |
| `ssh_stat` | Get metadata for a file or directory (size, mode in octal, uid/gid, mtime/atime, isFile/isDirectory/isSymbolicLink). Use instead of parsing `ls -la`. |
| `ssh_mkdir` | Create a directory via SFTP. Set `recursive: true` for `mkdir -p` behavior. Unlike the other SFTP tools, the path may be relative — it resolves against the SFTP working directory (normally the remote user's home). `~` is not expanded; SFTP has no shell. |
| `ssh_delete` | Delete a file or empty directory via SFTP. Auto-dispatches unlink vs rmdir based on the path's *own* type (`lstat`), so a symlink is always unlinked — never followed — including a dangling one or one pointing at a directory. Recursive directory delete is intentionally NOT supported -- use `ssh_exec rm -rf` if you need it. |

### Higher-level operations

Tools that wrap common patterns agents build with ssh_exec — faster and less error-prone.

| Tool | Description |
|------|-------------|
| `ssh_multi_exec` | Run a command on multiple hosts in parallel. Returns results per host. Optional `env` param sets per-call environment variables (same POSIX-safe prefix as `ssh_exec`, applied once and sent to every host). Subject to [command policy](#command-policy) if configured (policy is checked once, against the env-prefixed command, before fan-out). |
| `ssh_find` | Search for files remotely with structured parameters (`name`, `type`, `size`, `depth`, `newer` — match files modified more recently than a reference path). |
| `ssh_tail` | Read the last N lines of a file, optionally filtered by a grep pattern. |
| `ssh_service_status` | Check systemd service status (active, PID, uptime, description). Flags `isError` only when the unit could not be found / queried, not when an existing unit is intentionally stopped. |

### Auto-diagnostics

When any remote operation fails, ssh-mcp automatically runs diagnostics and includes the results in the error response. Your agent doesn't need to call `ssh_diagnose` separately — it gets told what's wrong and how to fix it right in the error message.

### Connection pooling

Remote operations reuse SSH connections automatically. When your agent makes multiple calls to the same host, the first call opens a connection and subsequent calls reuse it. Connections are kept alive for 60 seconds after the last use, then closed automatically.

The pool caps at 100 connections by default, and a connection still being dialed counts against the cap. When the cap is reached the pool closes an idle connection to make room. If every slot is in use or dialing, a tool call waits for one instead of failing:

- **A single-host remote tool** (`ssh_exec`, the SFTP tools, `ssh_find`, `ssh_tail`, `ssh_service_status`) waits up to its `timeout` (30s for the SFTP tools, which have no `timeout` parameter) and is next in line for the first slot that frees, so an `ssh_exec` arriving in the middle of a wide `ssh_multi_exec` runs between two of its hosts rather than being refused for the whole run. It reports `Connection pool is full` only if it never won a slot in that time.
- **`ssh_multi_exec`** runs at most `SSH_MCP_MAX_POOL_SIZE` hosts at once (default 100) and works through a longer list as slots free up, so raising the cap raises its parallelism; `timeout` is per host, not a bound on the whole call. When the pool is full it waits, and gives up only when none of its own hosts holds a slot and a full `timeout` has passed with none of them starting or finishing. The hosts waiting at that point (up to one per parallel slot) and every host still queued then report `Connection pool is full`; the queued ones are never attempted.

A call reaches `Connection pool is full` only when other calls — a long `ssh_exec`, a concurrent `ssh_multi_exec` — kept every slot from it for a full `timeout`; a fan-out wider than the cap that has the pool to itself never does, however long it runs. If you see it, rerun once those calls finish (for `ssh_multi_exec`, the hosts that reported it), or raise the cap with `SSH_MCP_MAX_POOL_SIZE=<n>` in the server's environment. The error names the variable.

The library's `acquire()` / `withConnection()` do not wait by default: they reject at once with a `PoolFullError` (`code: "ERR_SSH_MCP_POOL_FULL"`, `isPoolFullError()`) unless you pass `{ waitForCapacityMs }` — see [Programmatic usage](#programmatic-usage).

### SSH config support

All connections respect your `~/.ssh/config`. Host aliases, custom ports, usernames, identity files, and ProxyJump settings are used automatically. If you have `Host myserver` configured in your SSH config, just pass `host: "myserver"` — ssh-mcp resolves everything.

**ProxyJump / bastion hosts** are supported automatically. If your SSH config has `ProxyJump bastion` for a host, ssh-mcp connects through the bastion transparently. Chained proxies work too.

### Host key verification

All remote operations verify the server's host key against `~/.ssh/known_hosts`:

- **Known host, key matches** — accept.
- **Known host, key changed** — reject (MITM protection). The rejection message distinguishes a genuine key mismatch from "the server offered a key type your `known_hosts` entry doesn't cover", so a missing ed25519 line doesn't read as an attack.
- **Unknown host** — accept, unless `SSH_MCP_STRICT_HOST_KEY=1`.

**That last branch is trust-always, not TOFU.** Real trust-on-first-use pins the key it saw the first time and rejects a change afterwards. The connection path never writes to `known_hosts` — no tool adds an entry as a side effect of connecting — so connecting pins nothing: *every* connection to a ho