MCP server Ternimal

Ternimal

+------------------------------------------------------------------+
| \\\_\                                                            |
| \\\( ^>     t e r n                                              |
|  \\\=/      A minimal, portable, secure remote terminal with MCP |
|  ~~~~~                                                           |
+------------------------------------------------------------------+

Ternimal (terminal + minimal) is a minimal, portable, secure remote terminal: SSH-style shells, command exec, port forwarding and file copy over end-to-end TLS, reached directly or through a relay for NAT traversal. One project, four small binaries:

binary	role
tern	client: shells, exec, port forwarding, file copy, REST gateway, MCP server for AI agents
ternd	agent: hosts sessions for authenticated clients; listens directly or dials a relay
ternr	relay: bridges clients to agents behind NAT; a public rendezvous that only forwards opaque bytes
rtern	combined relay + client: catches an agent that dials in and drops you into its shell; one process instead of ternr + tern

Client-to-agent traffic is end-to-end TLS (clients pin the agent's certificate) and authentication to the agent is mandatory. This is an administration tool, not a stealth tool: connections are logged and the agent has no unauthenticated mode. Only use it on systems you own or are authorized to access.

Installation

Download the zip for your OS and architecture from the latest release, check it against SHA256SUMS and, with the GitHub CLI, its build provenance attestation, and put the four binaries on your PATH:

curl -LO https://github.com/ternimal/tern/releases/latest/download/ternimal-linux-amd64.zip
curl -LO https://github.com/ternimal/tern/releases/latest/download/SHA256SUMS
sha256sum --ignore-missing -c SHA256SUMS
gh attestation verify ternimal-linux-amd64.zip -R ternimal/tern
mkdir -p ~/.local/bin
unzip ternimal-linux-amd64.zip tern ternd ternr rtern -d ~/.local/bin

Or build them with Go 1.21 or later:

go install github.com/ternimal/tern/cmd/...@latest

Notes for macOS and Windows, building from source and the supported platforms are in docs/install.md.

Quick start

# agent: zero-config, listens on port 2222 on every IPv4 and IPv6 address,
# mints a token, prints its fingerprint
ternd

# client: connect by IP with the agent's fingerprint and token
TERN_TOKEN=<token> tern connect -a AGENT_IP:2222 -f <agent-fp>

Getting started also covers reaching an agent behind NAT through a relay, catching one with rtern and logging in with OpenSSH keys instead of a token.

AI agents (tern mcp)

tern mcp lets an AI client such as Claude Code, Claude Desktop or Cursor work on your agents through the Model Context Protocol, under a policy you set and with an audit log of every call. It is read-only by default, and asks you before the actions you choose.

In Claude Code, install tern first, then the Ternimal plugin:

claude plugin marketplace add ternimal/tern
claude plugin install ternimal@ternimal

The plugin starts tern from your PATH and reads your hosts from a config file, ~/.config/tern/mcp.json by default; its ternimal:setup skill walks you through writing one. plugin/README.md says what it runs and what it sends. Other clients, a one-line setup without a config file, the tools and the safety model are in docs/mcp.md.

Features

• Direct or relay: reach an agent on your LAN directly, or reach one behind NAT through a relay, so that agent needs no inbound port.
• End-to-end encryption: TLS and authentication run between client and agent, so a relay only forwards ciphertext.
• Keys or tokens: OpenSSH public keys in authorized_keys format, or a shared token.
• Resumable sessions: tern connect reconnects on its own after a drop and resumes the session with scrollback replay; others can join it as read-only viewers.
• One connection, many channels: one authenticated connection can carry a shell, exec, port forwards and file copy at once.
• REST gateway and MCP server: run commands over HTTP, or let AI agents work under a policy.
• Recording: with ternd --record-dir, the agent saves each session as an asciicast, playable with asciinema play.
• Zero-config: run ternd with no flags on a terminal and it mints a token and prints the line to connect with.
• Portable: Linux, macOS, Windows and Android on amd64 and arm64.

All of them in detail: docs/features.md.

Documentation

• Getting started: direct, through a relay, with rtern, with OpenSSH keys and the insecure flags for testing
• Commands: every tern command, sharing and resuming sessions, copying files, port forwards
• REST gateway: run commands on an agent over HTTP
• AI agents over MCP: the config file, profiles, tools, approvals and the audit log
• Install and build: checking a release, building from source, supported platforms
• Keys, tokens and files: the rules for the files tern reads
• Operating notes: listeners, shutdown, recordings and other details
• Security: the threat model, the dangerous flags and how to report a vulnerability
• Contributing: license terms, the CLA, development and the code layout

License

Ternimal is licensed under the GNU Affero General Public License v3.0 only (AGPL-3.0-only); see LICENSE. Running a modified version to provide a network service requires offering that version's source to its users.

A separate commercial license is available for uses that cannot comply with the AGPL, for example embedding Ternimal in a proprietary or hosted service; see NOTICE. Contributions are welcome; see CONTRIBUTING for the license terms and the CLA.

"Ternimal", the binary names (tern, ternd, ternr, rtern) and the project logo are project trademarks and are not licensed under the AGPL; see NOTICE.