termless

Headless terminals: test, record, replay, and run sessions.

termless is the umbrella package for the termless stack — an effect-style umbrella with arity-scoped subpaths, not a single flat namespace. Backend arity is visible in the import path: ., ./fmt, ./rec, and ./contract have no engine. ./backends is the only home of plurality.

If you never import termless/backends, you never have more than one engine.

The engine itself is vterm.js — a pure-TypeScript, zero-dependency terminal emulator targeting full VT/ECMA-48/xterm coverage, graded at arm's length by its own conformance rig.

Subpaths

| Subpath | Contains | Engine? | | ------------------- | ----------------------------------------------------------------------------------------------------------------------------------- | :-----: | | termless | createTerminal + the common path: screenshots, key mapping, diffing | no | | termless/contract | The Terminal read contract, TerminalBackend, region view types | no | | termless/fmt | The .tty / .ttyz recording format — types + read/write surface | no | | termless/rec | Recording, its codecs, journal-replay, and replay/view | no | | termless/backends | The backend registry — backend(), backends(), isReady, buildBackend() | yes | | termless/test | Reserved. Vitest matchers, fixtures, and snapshot assertions. Ships from @termless/test today. | no | | termless/session | Reserved. The sealed live-session API (session.readable/writable/recording). Unbuilt — see docs/reference/formats/tty.md. | no |

Quick start

import { createTerminal } from "termless"
import { backend } from "termless/backends"

const term = createTerminal({ backend: await backend("vterm"), cols: 80, rows: 24 })
term.feed("hello")
term.screen.getText() // "hello"
await term.close()

Working directly against a specific engine's own package (@termless/vterm, @termless/xtermjs, …) skips termless/backends entirely — that is the single-engine path, and it never imports plurality:

import { createTerminal } from "termless"
import { createVtermBackend } from "@termless/vterm"

const term = createTerminal({ backend: createVtermBackend(), cols: 80, rows: 24 })

Why an umbrella

Scoped @termless/* packages (@termless/core, @termless/vterm, @termless/xtermjs, …) remain the satellite packages — native/WASM backends stay scoped so their install weight (Rust builds, WASM blobs) is opt-in, not bundled into every install. termless is the single-semver front door: one version, one changelog, the subpaths above as its whole public surface. Native backends are the deliberate exception to "single semver" — their install cost is why they stay out.

Learn more

• termless.dev — full documentation, guides, and the cross-terminal conformance corpus.
• vterm.js — the engine: coverage, differential tests against the classic VT corpus, and the deliberate-divergence ledger.