chenglou/pretext · error · Error

Unsupported browser ${browser}; expected chrome or safari

Error message

Unsupported browser ${browser}; expected chrome or safari

What it means

parseBrowser constrains probe-check to Chrome or Safari. It reads --browser=, then the PROBE_CHECK_BROWSER env var, then defaults to 'chrome', lowercases, and throws for anything else (including firefox, edge, ie). probe-check is a focused single-case diagnostic; the broader Firefox/oracle automation lives in pre-wrap-check.ts and symbol-check.ts, and even there Firefox symbol runs are unsupported (see error 86).

Source

Thrown at scripts/probe-check.ts:82

function parseStringFlag(name: string): string | null {
  const prefix = `--${name}=`
  const arg = process.argv.find(value => value.startsWith(prefix))
  return arg === undefined ? null : arg.slice(prefix.length)
}

function parseNumberFlag(name: string, fallback: number): number {
  const raw = parseStringFlag(name)
  if (raw === null) return fallback
  const parsed = Number.parseInt(raw, 10)
  if (!Number.isFinite(parsed)) throw new Error(`Invalid value for --${name}: ${raw}`)
  return parsed
}

function parseBrowser(value: string | null): BrowserKind {
  const browser = (value ?? process.env['PROBE_CHECK_BROWSER'] ?? 'chrome').toLowerCase()
  if (browser !== 'chrome' && browser !== 'safari') {
    throw new Error(`Unsupported browser ${browser}; expected chrome or safari`)
  }
  return browser
}

function requireFlag(name: string): string {
  const value = parseStringFlag(name)
  if (value === null || value.length === 0) throw new Error(`Missing --${name}=...`)
  return value
}

function printReport(report: ProbeReport): void {
  if (report.status === 'error') {
    console.log(`error: ${report.message ?? 'unknown error'}`)
    return
  }

  console.log(
    `width ${report.width}: diff ${report.diffPx}px | lines ${report.predictedLineCount}/${report.browserLineCount} | height ${report.predictedHeight}/${report.actualHeight}`,

View on GitHub (pinned to ac49b09b7d)

Solutions

Use chrome (the default) or safari.
Unset or correct PROBE_CHECK_BROWSER if the throw names a value you did not pass on the CLI.
For Firefox diagnostics use the dedicated checkers (pre-wrap-check), not probe-check.

Example fix

# before
PROBE_CHECK_BROWSER=firefox bun run scripts/probe-check.ts --text=hi

# after
bun run scripts/probe-check.ts --text=hi                  # defaults to chrome
# or
bun run scripts/probe-check.ts --browser=safari --text=hi

Defensive patterns

Strategy: validation

Validate before calling

const PROBE_BROWSERS = ['chrome', 'safari'] as const
const candidate = (parseStringFlag('browser') ?? process.env['PROBE_CHECK_BROWSER'] ?? 'chrome').toLowerCase()
if (!PROBE_BROWSERS.includes(candidate as 'chrome' | 'safari')) {
  console.error(`probe-check supports chrome|safari only, got ${candidate}`)
  process.exit(2)
}

Type guard

const isProbeBrowser = (s: string): s is 'chrome' | 'safari' =>
  s === 'chrome' || s === 'safari'

Prevention

probe-check is chrome/safari only by design; Firefox diagnostics belong to the dedicated checkers.
Mind inherited PROBE_CHECK_BROWSER env vars when the throw names a value you did not pass on the CLI.
Default to chrome (omit --browser) unless you specifically need Safari extraction.

When it happens

Trigger: --browser=firefox; PROBE_CHECK_BROWSER=edge bun run scripts/probe-check.ts; a typo such as --browser=chrme. parseBrowser runs at line 145, before the browser session is created.

Common situations: Reusing a --browser=firefox habit from pre-wrap-check/symbol-check; a PROBE_CHECK_BROWSER env var left over from another tool; typo in the token.

Related errors

AI-assisted analysis of chenglou/pretext@ac49b09b7d (2026-08-12). Data as JSON: /api/errors/98789abfe1359296. Report an issue: GitHub.