[Bug]: WebKit on Linux sometimes closes the page without the beforeunload dialog on page.close({ runBeforeUnload: true })

// Repro: on page.close({ runBeforeUnload: true }), WebKit on Linux sometimes closes the page without the beforeunload
// dialog the page asked for. A synthetic page served by Node's http; no other code.
//
// Each repetition opens the page in a new context, fills its only field -- which makes the page prevent beforeunload --
// and closes the page with runBeforeUnload, waiting for the `dialog` event. Two arms, interleaved:
//   spa    -- open /, follow a link that pushStates to /form, fill the field.
//   direct -- open /form, click the field, fill it.
// The page writes to localStorage what its beforeunload saw: read afterwards from another page of the same context, it
// shows, for a repetition without a dialog, whether the event ran and was prevented.
//
//   BROWSER=webkit|chromium|firefox (default webkit)   REPEATS (default 300)   WORKERS (default 2)
import http from 'node:http'
import { chromium, devices, firefox, webkit } from 'playwright'

const BROWSER = process.env.BROWSER ?? 'webkit'
const REPEATS = Number(process.env.REPEATS ?? 300)
const WORKERS = Number(process.env.WORKERS ?? 2)
const types = { webkit, chromium, firefox }
const device = { webkit: devices['Desktop Safari'], chromium: devices['Desktop Chrome'], firefox: devices['Desktop Firefox'] }[BROWSER]

const html = `<!doctype html><meta charset="utf-8"><title>repro</title>
<a id="go" href="/form">Form</a><div id="app"></div>
<script>
let dirty = false
window.addEventListener('beforeunload', (event) => {
  if (dirty) { event.preventDefault(); event.returnValue = '' }
  localStorage.setItem('unload', JSON.stringify({ dirty, prevented: event.defaultPrevented, active: navigator.userActivation?.hasBeenActive ?? null }))
})
function show() {
  if (location.pathname !== '/form') return
  document.getElementById('app').innerHTML = '<label>Name <input id="name"></label>'
  document.getElementById('name').addEventListener('input', () => { dirty = true })
}
document.getElementById('go').addEventListener('click', (event) => { event.preventDefault(); history.pushState({}, '', '/form'); show() })
show()
</script>`

const server = http.createServer((_request, response) => {
	response.writeHead(200, { 'content-type': 'text/html; charset=utf-8' })
	response.end(html)
})
await new Promise((resolve) => server.listen(4400, '127.0.0.1', resolve))
const base = 'http://127.0.0.1:4400'

const browser = await types[BROWSER].launch()
console.log(`${BROWSER} ${browser.version()}`)
const results = []

async function once(index) {
	const arm = index % 2 === 0 ? 'spa' : 'direct'
	const context = await browser.newContext({ ...device })
	const page = await context.newPage()
	if (arm === 'spa') {
		await page.goto(`${base}/`)
		await page.click('#go')
	} else {
		await page.goto(`${base}/form`)
		await page.click('#name')
	}
	await page.fill('#name', 'Morning')
	let dialog = null
	const asked = page.waitForEvent('dialog').then(
		async (question) => {
			dialog = question.type()
			await question.dismiss()
		},
		() => undefined,
	)
	console.error(`MARK ${new Date().toISOString()} repetition ${index} (${arm}) closes`)
	await page.close({ runBeforeUnload: true })
	await asked
	const closed = page.isClosed()
	// What the page's beforeunload saw, from another page of the same context.
	const reader = await context.newPage()
	await reader.goto(`${base}/`)
	const unload = JSON.parse((await reader.evaluate(() => localStorage.getItem('unload'))) ?? 'null')
	await context.close()
	const line = { index, arm, dialog, closed, unload }
	results.push(line)
	console.log(JSON.stringify(line))
}

let next = 0
await Promise.all(
	Array.from({ length: WORKERS }, async () => {
		while (next < REPEATS) {
			const index = next++
			await once(index).catch((error) => console.log(JSON.stringify({ index, error: String(error) })))
		}
	}),
)
await browser.close()
server.close()

for (const arm of ['spa', 'direct']) {
	const mine = results.filter((line) => line.arm === arm)
	const missing = mine.filter((line) => line.dialog !== 'beforeunload')
	const prevented = missing.filter((line) => line.unload?.prevented === true)
	console.log(`SUMMARY ${BROWSER} ${arm}: ${mine.length} runs, ${missing.length} without a dialog, ${prevented.length} of them with beforeunload run and prevented`)
}

Run 2, 2026-10-11, PROTOCOL=1: 1 of 300 without a dialog (repetition 144, arm spa). Excerpt of DEBUG=pw:protocol.

Repetition 144 (pageProxyId 2237) -- no dialog:
2026-10-11T17:00:31.828Z pw:protocol SEND ► {"method":"Target.sendMessageToTarget", ... "Page.insertText","params":{"text":"Morning"}} (pageProxyId 2237)
2026-10-11T17:00:31.830Z pw:protocol ◀ RECV {"result":{},"id":17618,...,"pageProxyId":"2237"}
2026-10-11T17:00:31.838Z pw:protocol SEND ► {"id":17627,"method":"Playwright.closePage","params":{"pageProxyId":"2237","runBeforeUnload":true}}
2026-10-11T17:00:31.899Z pw:protocol ◀ RECV {"method":"Target.targetDestroyed","params":{"targetId":"page-2238","crashed":false},"browserContextId":"8000000000000092","pageProxyId":"2237"}
2026-10-11T17:00:31.900Z pw:protocol ◀ RECV {"method":"Playwright.pageProxyDestroyed","params":{"pageProxyId":"2237"}}
(no Dialog.* message for pageProxyId 2237 anywhere in the log)

Repetition 145 (pageProxyId 2249) -- the dialog comes, 36 ms after closePage:
2026-10-11T17:00:31.927Z pw:protocol SEND ► {"id":17655,"method":"Playwright.closePage","params":{"pageProxyId":"2249","runBeforeUnload":true}}
2026-10-11T17:00:31.963Z pw:protocol ◀ RECV {"method":"Dialog.javascriptDialogOpening","params":{"type":"beforeunload","message":""},"browserContextId":"8000000000000093","pageProxyId":"2249"}
2026-10-11T17:00:31.966Z pw:protocol SEND ► {"id":17658,"method":"Dialog.handleJavaScriptDialog","params":{"accept":false},"pageProxyId":"2249"}
2026-10-11T17:00:31.967Z pw:protocol ◀ RECV {"method":"Dialog.javascriptDialogClosed","browserContextId":"8000000000000093","pageProxyId":"2249"}