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1. naeemobuj-hub commented on May 28, 2026

   

   naeemobuj-hub

   on May 28, 2026

   More actions

   Environment

   • OS: Windows 11 Home 10.0.26200
   • Python: 3.12.10 (Windows Store distribution)
   • Default sys.stdout.encoding: cp1252
   • Playwright: Firefox 146.0.1 (playwright firefox v1509)
   • Webwright commit: 29fc4b4

   Summary

   The canonical "Browser launch skeleton" code block in skills/webwright/reference/playwright_patterns.md (lines 16–46) and the sibling pattern on line 65 both end with print(...aria_snapshot()). On any page whose accessibility tree contains characters outside cp1252 — for example an arxiv search results page, which carries U+25BD WHITE DOWN-POINTING TRIANGLE inside the "▽ More" abstract toggle — the print call crashes with UnicodeEncodeError under Windows's default cp1252 stdout encoding.

   A Windows user who copy-pastes the recommended explore skeleton from Webwright's own reference doc will hit this on the very first non-trivial page they look at. The "Final-script instrumentation" example on lines 129–166 is affected at line 143's print(line, end="") for the same reason (the file write uses open(..., encoding="utf-8") so the log file itself is fine, but the mirror print to stdout still hits cp1252).

   Reproduction

   Windows PowerShell, Python 3.12 default install, no PYTHONIOENCODING set

   python - <<'PY'
   import asyncio
   from playwright.async_api import async_playwright

   async def main():
   async with async_playwright() as pw:
   browser = await pw.firefox.launch(headless=True)
   ctx = await browser.new_context(viewport={"width": 1280, "height": 1800})
   page = await ctx.new_page()
   await page.goto(
   "https://arxiv.org/search/?query=browser+agent&searchtype=all",
   wait_until="domcontentloaded",
   )
   snapshot = await page.locator("body").aria_snapshot()
   print("ARIA:", snapshot)
   await browser.close()

   asyncio.run(main())
   PY

   Expected

   ARIA snapshot prints to stdout without crashing.

   Actual

   UnicodeEncodeError: 'charmap' codec can't encode character '▽' in position 4958: character maps to <undefined>
     File ".../Lib/encodings/cp1252.py", line 19, in encode
       return codecs.charmap_encode(input,self.errors,encoding_table)[0]
   

   Root cause

   Python on Windows defaults sys.stdout.encoding to cp1252 unless PYTHONIOENCODING=utf-8 is set in the environment or the script explicitly reconfigures stdout. Playwright's aria_snapshot() returns the full accessibility tree as a string that frequently contains non-cp1252 glyphs from the page (typography symbols, emoji, CJK characters, math symbols).

   Suggested fix

   At the top of every code skeleton in skills/webwright/reference/playwright_patterns.md (the "Browser launch skeleton" example and the "Final-script instrumentation" example), force utf-8 stdout:

   import sys
   sys.stdout.reconfigure(encoding="utf-8")
   Add a short "Windows note" callout next to the skeleton explaining why this line is needed. The fix is portable (no-op on POSIX where stdout is already utf-8) and keeps the patterns reliable on the platform where the bug bites hardest.

   Happy to send a PR.
2. Ray Kuo (raykuo998)

   added a commit that references this issue on Jun 23, 2026

   docs: force utf-8 stdout in playwright_patterns skeletons (Windows cp…

   ...

   This issue will close once commit 4a1e641 is merged into the 'main' branch.

   4a1e641