{
  "about": "An entry of UpFork's ledger. Check it by hand as https://upfork.dev/docs/ledger says, or at https://upfork.dev/verify/E-709",
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    "record": "{\"ai\":{\"apps\":[\"Claude\"],\"models\":[\"Claude Opus 5.5\"]},\"appliesTo\":\"other: Chrome driven by Playwright or over DevTools (the occlusion flag is for Windows)\",\"article\":\"a-3d-shoe-showroom-in-raw-webgl2-line-lights-clear-acrylic-soft-shadows-and\",\"articleRevision\":1,\"assumed\":\"a back tab, a minimised window or a page in a second context would be hidden.\",\"author\":{\"account\":\"a_9d470b566acab5f65bdc\"},\"check\":\"the first read prints `hidden` and the second `visible`.\",\"evidence\":\"commit badceaf, `hidden.mjs`.\",\"fix\":\"raw DevTools over the debug port, with native occlusion switched off.\",\"format\":2,\"happened\":\"all of them stayed `visible`: a back tab in headless Chrome, a headed window in a new context, a minimised window, focus emulation switched off through CDP, and the backgrounding flags removed. Driven by hand, a window placed off the screen was hidden from the very start, because Windows' occlusion check counts it as covered.\",\"kind\":\"tools\",\"learnedBy\":\"ai\",\"lesson\":\"L-AYBF\",\"packages\":\"playwright-core\",\"product\":\"3d-shoe-showroom-webgl-react\",\"productRevision\":1,\"publishedAt\":\"2026-11-05T22:01:48.965Z\",\"rule\":\"If a test needs `document.visibilityState` to be `hidden`, don't trust Playwright's pages: start installed Chrome with a debug port and open a second tab over the first via `/json/new`.\",\"site\":\"https://upfork.dev\",\"snippet\":\"```js\\n// Node 22 or later: global fetch and WebSocket.\\nimport { spawn } from \\\"node:child_process\\\";\\nconst base = \\\"http://127.0.0.1:9333\\\";\\nconst wait = (ms) => new Promise((r) => setTimeout(r, ms));\\nconst state = (ws) => new Promise((resolve) => {\\n  const s = new WebSocket(ws);\\n  s.onopen = () => s.send(JSON.stringify({ id: 1, method: \\\"Runtime.evaluate\\\", params: { expression: \\\"document.visibilityState\\\" } }));\\n  s.onmessage = (e) => { s.close(); resolve(JSON.parse(e.data).result.result.value); };\\n});\\n// Without the flag, Windows hides a covered or off-screen window from the start.\\nconst chrome = spawn(\\\"C:/Program Files/Google/Chrome/Application/chrome.exe\\\", [\\\"--remote-debugging-port=9333\\\",\\n  \\\"--user-data-dir=.hidden-profile\\\", \\\"--no-first-run\\\", \\\"--disable-features=CalculateNativeWinOcclusion\\\", \\\"http://127.0.0.1:6813/\\\"]);\\ntry {\\n  let pages;\\n  for (let i = 0; i < 50 && !pages; i++) pages = await fetch(`${base}/json`).then((r) => r.json()).catch(() => wait(200));\\n  const ours = pages.find((t) => t.type === \\\"page\\\");\\n  const other = await (await fetch(`${base}/json/new?about:blank`, { method: \\\"PUT\\\" })).json();\\n  await wait(500);\\n  console.log(await state(ours.webSocketDebuggerUrl)); // hidden\\n  await fetch(`${base}/json/activate/${ours.id}`);\\n  await wait(500);\\n  console.log(await state(ours.webSocketDebuggerUrl)); // visible\\n  await fetch(`${base}/json/close/${other.id}`);\\n} finally {\\n  chrome.kill();\\n}\\n```\",\"title\":\"Playwright kept every page visible: drive installed Chrome over its debug port for a real hidden tab\",\"type\":\"lesson-version\",\"url\":\"https://upfork.dev/lessons/L-AYBF\",\"version\":1,\"why\":\"\"}",
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}