TermDeck

TermDeck is a Linux daemon and CLI for persistent PTY-backed terminal sessions. It lets automation start a shell, send commands, poll output, detect prompts, inspect logs, and expose an observe-only web view without giving browser users terminal input capability.

TermDeck targets agent workflows where the terminal must outlive one CLI invocation. The daemon owns the PTY. The CLI and web UI connect to the daemon over local transports.

Status

• Platform: Linux
• Runtime: Node.js 22+
• Package manager used by this repo: pnpm
• Release artifact: GitHub Release tarball
• Web UI: observe-only

Features

• Persistent PTY sessions via node-pty
• Local daemon: termdeckd
• CLI: termdeck
• MCP server: termdeck-mcp
• Length-prefixed protobuf CLI-to-daemon protocol over Unix socket
• Server-side terminal buffer via @xterm/headless
• Observe-only web UI with JSON REST control endpoints and binary protobuf WebSocket events
• Prompt/state classification: running, ready, repl, password, confirm, editor, pager, continuation, eof
• Session artifacts: transcript, events, commands, interactions, metadata, state
• Shell command markers for run output boundaries and exit-code capture
• Historical inspection: history, inspect, log, events, replay
• Password input path that avoids command logging
• Linux foreground process-group signal targeting via /proc/<pid>/stat tpgid

Install

Download the release tarball from GitHub Releases or install from a local checkout.

pnpm install
pnpm run build

node-pty is a native dependency. pnpm must allow its build script. This repo includes:

only-built-dependencies[]=node-pty

The package postinstall check fails fast if the native binding is missing.

Documentation

• Usage Guide
• Scenarios
• Chinese README

Quick start

Start the daemon:

termdeckd

Create a session:

termdeck new main --cwd "$PWD"

Or let an agent step create it on first use:

termdeck step main 'pwd && ls' --cwd "$PWD" --timeout-ms 5000 --autostart

Or use a project-derived session name so callers do not have to manage one:

termdeck project-step 'pwd && ls' --cwd "$PWD" --timeout-ms 5000 --autostart

Run a command:

termdeck run main 'pwd && ls' --timeout-ms 5000

Poll new output:

termdeck poll main --quiescence-ms 200

Check the current state with a rendered screen tail:

termdeck state main --lines 12

Read the rendered screen as plain text:

termdeck screen main

Open the observe-only web UI:

TERMDECK_WEB_PORT=8787 termdeckd
# browse http://127.0.0.1:8787

The CLI defaults to agent-readable text. --raw prints PTY bytes for debugging. Web rendering uses serialized xterm state and raw live events.

CLI commands

Session lifecycle:

termdeck new <session> --cwd <path> [--shell <shell>] [--rows N] [--cols N] [--prompt-regex <regex>]
termdeck list
termdeck kill <session>
termdeck resize <session> --rows N --cols N
termdeck configure <session> [--prompt-regex <regex>]

Terminal I/O:

termdeck step <session> [command] [--cwd <path>] [--op run|poll|send|paste|ctrl|signal] [--timeout-ms N] [--startup-timeout-ms N] [--quiescence-ms N] [--lines N] [--autostart]
termdeck project-step [command] [--cwd <path>] [--name <label>] [--op run|poll|send|paste|ctrl|signal] [--timeout-ms N] [--autostart]
termdeck run <session> <command> [--timeout-ms N] [--quiescence-ms N]
termdeck script <session> [file] [--inline <script>] [--shell bash] [--timeout-ms N] [--quiescence-ms N]
termdeck paste <session> [file] [--inline <text>] [--enter] [--timeout-ms N] [--quiescence-ms N]
termdeck send <session> <data> [--timeout-ms N] [--quiescence-ms N]
termdeck ctrl <session> <key> [--timeout-ms N] [--quiescence-ms N]
termdeck poll <session> [--timeout-ms N] [--quiescence-ms N]
termdeck password <session> [--timeout-ms N] [--quiescence-ms N]
termdeck signal <session> <signal> [--timeout-ms N] [--quiescence-ms N]

Inspection:

termdeck state <session> [--lines N] [--autostart]
termdeck summary <session> [--lines N] [--events N] [--autostart]
termdeck last-command <session>
termdeck search <query> [--session ID] [--cwd PATH] [--task NAME] [--kind transcript,events,commands,metadata,tasks] [--regex] [--limit N] [--context N]
termdeck screen <session>
termdeck scrollback <session> [--lines N]
termdeck transcript <session>
termdeck metadata <session>
termdeck history
termdeck inspect <session>
termdeck log <session> [--lines N]
termdeck events <session> [--after-seq N] [--limit N]
termdeck replay <session> [--lines N]
termdeck clear-scrollback <session>

Background task helpers:

termdeck task start <name> <command> --cwd <path> [--owner USER] [--labels a,b] [--ttl-ms N] [--restart-policy never|on-exit|on-failure] [--max-restarts N] [--backoff-ms N] [--ready-url URL] [--ready-port N] [--expect PATTERN]
termdeck task status <name>
termdeck task recover <name>
termdeck task logs <name> [--lines N]
termdeck task list
termdeck task dashboard
termdeck task prune [--stale] [--expired] [--dry-run]
termdeck task stop <name>

Session cleanup:

termdeck list [--cwd <path>] [--name <text>] [--status ready|running|repl|password|confirm|editor|pager|eof|unknown]
termdeck prune [--cwd <path>] [--name <text>] [--status STATUS]

MCP server

termdeck-mcp exposes the same TermDeck capability surface as the CLI over stdio MCP. CLI, MCP, and the web UI are peer access surfaces; termdeckd remains the owner of PTYs, sessions, transcripts, and web observation.

Register the server directly. When no environment is provided, CLI and MCP discover an existing daemon by checking the system socket at /var/lib/termdeck/termdeckd.sock before falling back to ~/.termdeck/termdeckd.sock. Agents do not need to choose a backend.

[mcp_servers.termdeck]
command = "termdeck-mcp"

Set TERMDECK_HOME or TERMDECK_SOCKET only when you intentionally want project-isolated state or a non-default daemon.

The MCP step tool is the agent-friendly default entrypoint. It discovers or autostarts termdeckd by default, creates a missing session when cwd is supplied, and returns stable JSON fields such as status, reason, prompt, exitCode, timedOut, outputTruncated, lastSeq, transcriptPath, and cwd. project_step goes one level higher by deriving a stable session id from cwd and an optional label.

summary returns a compact inspection object with a screen tail, output tail, recent events, and likely error lines. last_command returns structured command id, command text, seq bounds, duration, exit code, timeout flag, and output tail. Use these when an agent needs state without replaying a large transcript.

search scans local sessions and task metadata across transcripts, events, commands, session metadata, and task specs. It supports filters for session id, task name, cwd, kind, regex, limit, and context lines. The Web UI exposes the same search for human inspection.

Agent-facing text views redact common secret-shaped values by default, including returned output, log/events views, summaries, and last-command records. Web snapshots and WebSocket output remain visible because the web surface is a local human observer. Raw transcripts remain local artifacts and should still be treated as sensitive.

Task helpers report stale metadata, expired TTLs, exited backing processes, restart counts, readiness diagnostics, and orphan task-* sessions. Optional restart policies can restart exited tasks on any exit or only non-zero exit. The web UI surfaces the same dashboard data with filters for active and attention-needed work, task logs, search results, and safe task stop/recover/prune controls.

Synchronization:

termdeck expect <session> <pattern> [--timeout-ms N]
termdeck expect-prompt <session> [--timeout-ms N]

Daemon configuration

Environment variables:

Variable	Default	Meaning
TERMDECK_HOME	discovered daemon, then ~/.termdeck	Runtime state root
TERMDECK_SOCKET	$TERMDECK_HOME/termdeckd.sock	Unix socket path
TERMDECK_WEB_PORT	unset	Starts web UI on 127.0.0.1:<port>

Socket permissions are set to 0600.

Data layout

Each session lives under:

$TERMDECK_HOME/sessions/<session>/

Files:

transcript.log      raw PTY output
commands.log        logged commands, excludes password input
interaction.log     input/output interaction stream
events.jsonl        sequenced daemon events
session.json        session metadata
state.json          latest detected state

Protocol

CLI clients use length-prefixed protobuf frames over the Unix socket. Terminal event subscribers use binary protobuf WebSocket frames. Web REST endpoints intentionally return JSON because they are low-frequency control and snapshot endpoints.

Development

pnpm install
pnpm run gen
pnpm run typecheck
pnpm run lint
pnpm test
pnpm run build
pnpm pack

CI runs typecheck, lint, tests, and build on GitHub Actions.

Limitations

• Linux only.
• Exact terminal semantics still depend on node-pty and the host shell.
• Signal targeting uses Linux /proc/<pid>/stat tpgid; if unavailable or stale, TermDeck falls back to process-group or process signaling.
• The web UI is observe-only by design. It does not accept human terminal input.
• The browser event decoder handles the current event schema only.

License

MIT