Tiny TypeScript helper for OSC 9;4 terminal progress sequences (used by terminals like Ghostty / WezTerm / Windows Terminal).

pnpm add osc-progress

import process from 'node:process'
import { startOscProgress } from 'osc-progress'

const stop = startOscProgress({
  label: 'Fetching',
  write: (chunk) => process.stderr.write(chunk),
  env: process.env,
  isTty: process.stderr.isTTY,
})

// ...do work...

stop()

Indeterminate (spinner-like) mode:

import { startOscProgress } from 'osc-progress'

const stop = startOscProgress({ label: 'Waiting', indeterminate: true })
// ...
stop()

Strip OSC progress from stored logs:

import { sanitizeOscProgress } from 'osc-progress'

const clean = sanitizeOscProgress(text, /*keepOsc*/ process.stdout.isTTY)

Returns true when emitting OSC 9;4 progress makes sense.

Heuristics:

• requires a TTY
• enables for TERM_PROGRAM=ghostty*, TERM_PROGRAM=wezterm*, or WT_SESSION (Windows Terminal)

Optional overrides:

• options.disabled / options.force
• options.disableEnvVar / options.forceEnvVar (expects = "1")

Starts a best-effort progress indicator and returns stop(): void.

Notes:

• label is appended as extra payload; not part of the canonical OSC 9;4 spec (many terminals ignore it, some show it).
• default is a timer-driven 0% → 99% progression (never completes by itself).
• terminator defaults to st (ESC \\); bel is also supported.

Returns a small stateful controller:

• setIndeterminate(label)
• setPercent(label, percent)
• clear()

Use this when you already have real progress (bytes/total, seconds/total) and want determinate terminal progress instead of the timer-based ramp.

Notes:

• returns no-op methods when supportsOscProgress(...) is false
• percent is rounded and clamped to 0..100
• clear() uses the last label (or the initial options.label if nothing was set yet)

import process from 'node:process'
import { createOscProgressController } from 'osc-progress'

const osc = createOscProgressController({
  env: process.env,
  isTty: process.stderr.isTTY,
  write: (chunk) => process.stderr.write(chunk),
})

osc.setIndeterminate('Connecting')
osc.setPercent('Downloading', 12)
osc.setPercent('Downloading', 67)
osc.clear()

Removes OSC 9;4 progress sequences (terminated by BEL, ST (ESC \\), or 0x9c).

OSC 9;4 is widely implemented, but state 4 is ambiguous across terminals (some treat it as paused, some as warning). This library exposes the raw numeric state and does not try to reinterpret it.