# Python crash when phone-side JavaScript runs
**URL:** https://forum.repebble.com/t/python-crash-when-phone-side-javascript-runs/794
**Category:** Watchapp/Face Developers Corner
**Created:** [June 1, 2026, 10:42am UTC](https://forum.repebble.com/t/python-crash-when-phone-side-javascript-runs/794 "2026-06-01T10:42:09Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@PotatoFi](https://forum.repebble.com/u/PotatoFi)
#### Post date: [June 1, 2026, 10:42am UTC](https://forum.repebble.com/t/python-crash-when-phone-side-javascript-runs/794/1 "2026-06-01T10:42:09Z")
I develop Pebble applications locally on macOS Tahoe 26.5. Recently when running `pebble build && pebble install --emulator [aplite-emery]`, QEMU and my C app launches just fine, but Python crashes and my phone side JavaScript application doesn’t run.
I gave Claude the output from the crash and it pointed me towards an issue with [STPyV8](https://github.com/cloudflare/stpyv8).
I am suspecting some issue with my Python 3.14 installation, it seems like some issue with Python that `pebble-tool` uses, and Python that has been installed by Brew for other stuff on my system. Maybe a symlink problem?
I’m in a bit over my head on this one. Has anyone else seen this happen?
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### Author:  [@jpx](https://forum.repebble.com/u/jpx)
#### Post date: [June 1, 2026, 12:35pm UTC](https://forum.repebble.com/t/python-crash-when-phone-side-javascript-runs/794/2 "2026-06-01T12:35:26Z")
python 3.14 explicitly not supported right now as mentioned on [Installing the Pebble SDK // Pebble Developers](https://developer.repebble.com/sdk/)
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### Author:  [@PotatoFi](https://forum.repebble.com/u/PotatoFi)
#### Post date: [June 3, 2026, 1:42pm UTC](https://forum.repebble.com/t/python-crash-when-phone-side-javascript-runs/794/3 "2026-06-03T13:42:58Z")
Whoops, I accidentally read that as _3.14 or lower._ That probably means that this is an easy fix. Sorry for the trouble!
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### Author:  [@PotatoFi](https://forum.repebble.com/u/PotatoFi)
#### Post date: [June 10, 2026, 7:45pm UTC](https://forum.repebble.com/t/python-crash-when-phone-side-javascript-runs/794/4 "2026-06-10T19:45:57Z")
I was mistaken, this doesn’t seem to be a Python issue (I’ve got 3.13.13 available), but something in STPYv8.
It looks like it crashes when I try to use `date.toLocaleString()` in my JS. Claude thinks it’s something to do with ICU, specific icu4c (not icu4j, weirdly? I don’t know how STPYv8 works).