aiterm-mcp

(日本語: README.ja.md)

Let Claude — or any MCP client — drive a real, persistent shell. One terminal stays open; ssh, docker exec, a REPL are just text you send into it, so the AI stops reconnecting for every single command. Reads come back token-reduced.

MCP = Model Context Protocol — the open standard that lets tools like Claude Code plug capabilities into an AI.

Just six tools — pty_open / pty_send / pty_read / pty_key / pty_close / pty_list. The backend is tmux, so sessions survive even if the MCP server or the AI client restarts.

Status: actively maintained · runs on Linux · WSL2 · macOS · native Windows · MIT · see the CHANGELOG.

Why

Send an AI one command at a time and, over SSH, every command becomes its own connect → authenticate → disconnect. That stings three ways: you re-authenticate every time (passphrase, one-time code, all of it), short-lived sessions pile up, and once connections come too fast your own defenses lock you out — fail2ban bans you, MaxStartups/MaxSessions reject you, the account gets locked. The security meant to stop attackers ends up stopping you. (Yes — this bit me on my own box. I built aiterm to drive my homelab from Claude Code without that re-auth hell.)

aiterm holds one PTY persistently and you ssh host (or docker exec -it x bash) inside it, once. Every command after that rides the same already-authenticated session: authenticate once, one session, nothing for the defenses to trip on. Session kind is never a tool-level distinction.

pty_open()                         → grab one local terminal
pty_send(id, "ssh 192.168.1.2")    → authenticate once, inside that terminal
pty_send(id, "uname -a")           → every later command rides the SAME session
pty_read(id, { wait: true })       → read the reduced output

Demo

Real captured output from a live session — the token reduction and completion detection are genuine, not mocked. The bracketed meta line is exactly what pty_read appends.

A noisy git log, read back token-reduced (458 → 273 tokens):

→ pty_send("demo", "git log --oneline -12")
→ pty_read("demo", { wait: true })
← 3ce487e (HEAD -> main, origin/main) docs(readme): lead the Why with the SSH pain …
  39a9668 (tag: v0.4.0) release: v0.4.0 — nested completion early-return …
  c1ed87b feat(completion): early-return nested status when nested + no until …
  … 9 more commits …
  [aiterm demo: 13 lines / ~273 tok (raw 13 lines / ~458 tok)] [is_complete=True via quiescent]

A grep, folded by the per-command reducer to just the hits (127 → 46 tokens):

→ pty_send("demo", "grep -rn capture-pane src/ test/")
→ pty_read("demo", { wait: true, rtk: true })
← 2 matches in 1 files:
  src/core.ts:159: // maxBuffer … capture-pane (large scrollback) …
  src/core.ts:329: const args = ["capture-pane", "-p", "-J", "-t", name];
  [aiterm demo: rtk:grep applied / ~46 tok (raw ~127 tok)] [is_complete=True via quiescent]

Nesting is just text you send in — here a Python REPL inside the same PTY:

→ pty_send("demo", "python3")
→ pty_read("demo", { until: ">>> " })             # nested prompt = "the inner shell is ready"
→ pty_send("demo", "print(sum(range(1_000_000)))")
→ pty_read("demo", { until: ">>> " })
← 499999500000                                     [is_complete=True via until]

ssh host and docker exec -it … bash nest exactly the same way (see Why) — an animated GIF of the full SSH flow is on the way; everything above is real output, not a script. While nested, pass until (the inner prompt) or mark: true, because quiescence cannot fire there by design — see Completion detection and Known constraints. A human can attach to the same tmux socket and watch any of this live (see A human can watch).

Quickstart (≈60 seconds)

One command registers it in Claude Code — no clone, no build, npx fetches it each run:

claude mcp add --scope user --transport stdio aiterm -- npx -y aiterm-mcp

Restart Claude Code, then verify the connection:

/mcp        # aiterm should show as connected, exposing 6 tools

Your first session — four calls, one persistent terminal:

pty_open()                          → { session_id: "t1", attach: "tmux -S … attach -t t1" }
pty_send("t1", "echo hello")        → command sent into the PTY
pty_read("t1", { wait: true })      → "hello"   (token-reduced, completion detected)
pty_close("t1")                     → terminal released

That's it. The terminal in t1 is real and persistent — ssh, docker exec, a REPL are just text you pty_send into it.

Prefer a global install, or a different client?

# install globally, then register the command name
npm i -g aiterm-mcp
claude mcp add --scope user --transport stdio aiterm -- aiterm-mcp

This registers it in ~/.claude.json; you'll get an approval prompt the first time. Any other MCP client (Cursor, Cline, Claude Desktop, …) works too — just launch npx -y aiterm-mcp (or aiterm-mcp) over stdio. Needs Node ≥ 18 and tmux — see Requirements.

How it works

flowchart LR
    AI["AI / MCP client"] -->|"pty_send"| S["aiterm-mcp<br/>stdio MCP · 6 tools"]
    S -->|"pty_read<br/>token-reduced"| AI
    S -->|"tmux send-keys<br/>capture-pane"| P["one local PTY<br/>tmux · persistent"]
    P -->|"ssh · docker · repl"| R["nested<br/>remote · container · REPL"]

One PTY is the only primitive. Everything else — SSH, containers, REPLs — is just text you pty_send into it. Because the PTY lives in tmux, sessions outlive the MCP server and the AI client.

vs. the alternatives

Requirements

• Node.js >= 18
• tmux (runtime prerequisite; check with tmux -V. Install with apt install tmux / brew install tmux)
  • macOS / Linux / WSL2 run tmux directly. On macOS install it with brew install tmux (stock macOS ships none). If your MCP client is launched from the GUI rather than a terminal, Homebrew's bin (/opt/homebrew/bin on Apple Silicon, /usr/local/bin on Intel) may be off its PATH; aiterm auto-searches those locations, or set AITERM_TMUX=/path/to/tmux to point at it explicitly.
  • Native Windows has no tmux, so aiterm transparently runs tmux inside WSL. It needs WSL installed and initialized, with tmux installed inside your WSL distro (sudo apt install tmux); verify with wsl tmux -V. Sessions, the socket, and human attach all live on the WSL side — the AI just drives them from the Windows-side command. (You reach Windows tools the same way you reach SSH: pty_send "powershell.exe …" nests into PowerShell.)
• Optional: the rtk binary (used by pty_send's rtk: true delegation; works fine without it)

Tools

Completion detection (4 layers)

pty_read({ wait: true }) decides "is the command done?" via four layers: process exit / until regex match / output is quiescent ∧ the shell is back (quiescence) / timeout. While nested (inside SSH), the "shell is back" check cannot fire, so pass until with the remote prompt for a clean decision.

Token reduction

• pty_read by default strips control characters, collapses repeated lines, and folds long output into head+tail (with a restore hint and a meta line).
• pty_read({ rtk: true }) further shrinks the observed output with a per-command reducer (git status/git log/grep/pytest and more) — a self-contained reimplementation that needs no rtk binary.
• pty_send({ rtk: true }) rewrites a known command into rtk form before sending, so reduction happens at the source if rtk exists there (passthrough otherwise).

Safety

Before sending, pty_send blocks destructive commands (rm -rf /, mkfs, dd of=/dev/…, DROP TABLE, …) — pass force: true to override — and sanitizes ESC / bracketed-paste terminators. pty_read neutralizes control characters in what it returns.

A human can watch

Sessions live on a shared tmux socket. The tmux -S … attach -t <id> line printed by pty_open lets a human attach to the same terminal and intervene (Ctrl-b d to detach). On native Windows the printed line is the WSL form — wsl tmux -S … attach -t <id> — since the session lives inside WSL.

Development

npm install
npm run build      # tsc → dist/
npm test           # build, then the node:test regression suite (requires tmux)
npm link           # put `aiterm-mcp` on PATH locally

Logic lives in src/core.ts (tmux control, reduction, completion detection, safety) and src/rtk.ts (per-command reducers); src/index.ts is the MCP surface. The design origin and the reducer's porting source (the pytest reducer is ported to be byte-exact with upstream rtk 0.42.0, locked by regression tests) are in prototype/python/.

Known constraints (by design, not bugs)

• While nested (ssh / docker / REPL), quiescence cannot fire by design, because the foreground command is no longer in the shell set (bash/sh/zsh/fish/dash). When nested with no until, pty_read({ wait: true }) returns early as is_complete=False via nested (rather than burning the full timeout, since no signal can confirm completion there) with a note to pass until (a regex for the prompt) or mark: true (an exit-code sentinel) for a confirmed completion.
• is_complete=False is not a failure. It means "completion was not observed within timeout." For long commands, raise timeout or use until/mark.
• The destructive gate is a tripwire, not a sandbox. It blocks common destructive forms only. It does not catch relative-path rm, things that become dangerous after $VAR expansion, or commands run on the far side of an SSH session.
• pty_send({ rtk: true }) is single-line only and needs the external rtk binary (passthrough without it). The pty_read({ rtk: true }) reducer, by contrast, is self-contained and rtk-independent.
• The pytest reducer matches rtk 0.42.0 on test counts, the rule line, and FAILURES-block formatting (locked by regression tests). It deliberately preserves the full failure reason on the FAILED summary lines (emitted under -ra/-rf), whereas rtk 0.42.0 truncates the reason at the first " - " — a readability choice, so those lines are intentionally not byte-identical to rtk. The [full output: …] tee-pointer line rtk appends on large output is not reproduced on the read side.
• tmux is started with -f /dev/null, so it does not read ~/.tmux.conf (to keep behavior reproducible across machines).
• All sessions live on a single socket (claude.sock). tmux … kill-server removes them all.

Try it

One command, no clone, no build:

claude mcp add --scope user --transport stdio aiterm -- npx -y aiterm-mcp

If aiterm saved you a round-trip of tokens, star the repo — it's the cheapest way to help others find it.

• npm: https://www.npmjs.com/package/aiterm-mcp
• Issues / bug reports: https://github.com/kitepon-rgb/aiterm-mcp/issues

License

MIT