Chrome Aw Snap! STATUS_BREAKPOINT for pyodide, with Antivirus such as Cylance or Sophos

[gf-amahoney]

Been finding this mainly on windows machines with chrome or edge, after pyodide apps load all the wheels and start the main entrypoint, they can just crash to the (Sad folder face) "Aw, Snap! Something went wrong while displaying this webpage. Error code: STATUS_BREAKPOINT".

With custom pyodide apps built with 1.92.700 and earlier versions. Even simply the https://traineq.org/probabl/ demo page.

It's a strange non-reproducible thing, multiple reloads sometimes works. Sometimes it will load and then crash after 1 sec. Other times, once it is fully loaded it is pretty stable.

Hard to get much from chrome logging, --v=1 --enable-logging=stderr will just end with nothing logged when STATUS_BREAKPOINT shows up, and the browser just completely nukes the dev tools, console, etc so can't see any debugging info there.

Have you run into this or heard of this for pyodide apps? Not having any issues on linux with chrome, just windows.

Very little from google searching but one example in the wild: pyodide/pyodide#4774

[pthom]

Library author here, thanks for your report!

This seems like a severe problem, so I would like more info : I cannot reproduce your issue at the moment (tried on Chrome + Edge on Windows 11 ARM).

I would need more details:

Did you try with another windows PC?

Please do try with another PC. This will give us more insight about the issue.

Do you have issues with the bare pyodide REPL demo?

https://pyodide.org/en/stable/console.html

This will load only pyodide. If you have issues in here, then pyodide is the likely culprit.

When it fails, are you able to see anything in the logs before the dev tools fail?

Below is a common startup sequence in the logs, up to where does it go?

# loading pyodide
# =====================
Showing loading modal [ui.js:14:13](http://localhost:6456/playground/js/ui.js)
Progress: 0% - Loading Pyodide... [ui.js:9:13](http://localhost:6456/playground/js/ui.js).   
Initializing Tippy.js tooltips [main.js:43:13](http://localhost:6456/playground/js/main.js)
The WebAssembly exception handling 'try' instruction is deprecated and should no longer be used. Please recompile to use the 'try_table' instruction instead.


# pyodide loaded and running, run small python code to show version
# ==========================================
Python version: 3.13.2 (main, Jan 28 2026, 03:36:02) [Clang 21.0.0git ([https:/github.com/llvm/llvm-project](https://github.com/github.com/llvm/llvm-project) 2f05451198e2f222ec66cec489 [pyodide_loader.js:63:17](http://localhost:6456/playground/js/pyodide_loader.js)


# load some packages
# ==========================================
Progress: 20% - Loading micropip [ui.js:9:13](http://localhost:6456/playground/js/ui.js)
Loading micropip [pyodide.asm.js:8:671379](https://cdn.jsdelivr.net/pyodide/v0.29.3/full/pyodide.asm.js)
Loaded micropip [pyodide.asm.js:8:671379](https://cdn.jsdelivr.net/pyodide/v0.29.3/full/pyodide.asm.js)
Base URL: http://localhost:6456/playground/ [pyodide_loader.js:75:17](http://localhost:6456/playground/js/pyodide_loader.js)
Progress: 60% - Installing imgui_bundle... [ui.js:9:13](http://localhost:6456/playground/js/ui.js)
The WebAssembly exception handling 'try' instruction is deprecated and should no longer be used. Please recompile to use the 'try_table' instruction instead.
../local_wheels/imgui_bundle-1.92.700-cp313-cp313-pyodide_2025_0_wasm32.whl loaded. [pyodide_loader.js:112:21](http://localhost:6456/playground/js/pyodide_loader.js)
Progress: 100% - Installing numpy... [ui.js:9:13](http://localhost:6456/playground/js/ui.js)
Loading numpy [pyodide.asm.js:8:671379](https://cdn.jsdelivr.net/pyodide/v0.29.3/full/pyodide.asm.js)
The WebAssembly exception handling 'try' instruction is deprecated and should no longer be used. Please recompile to use the 'try_table' instruction instead.
Loaded numpy [pyodide.asm.js:8:671379](https://cdn.jsdelivr.net/pyodide/v0.29.3/full/pyodide.asm.js)
numpy loaded. [pyodide_loader.js:112:21](http://localhost:6456/playground/js/pyodide_loader.js)
Progress: 100% - All packages loaded. [ui.js:9:13](http://localhost:6456/playground/js/ui.js)
Pyodide and packages loaded.


# all packages loaded, the app will start
# ==========================================

Can you try the minimal app source code and use it to make more diagnostic

• Download https://imgui-bundle.pages.dev/min_pyodide_app/demo_heart.source.txt into an html file.
• Serve this file (e.g python -m http.server), and open it in a browser
• Then comment out some parts, for example:
  • do not download the imgui-bundle package, and run a very simple python app (print("hello")
  • just import imgui_bundle and print its version (__version__)

[pthom]

I just did an intensive test on another Windows PC (x64) and I could not reproduce the issue on Chrome and Edge although I restarted Chrome several times and reloaded the page about 30 times.

This looks similar to this issue on the pyodide repo: Chrome crashed with "Aw, Snap!" on Windows due to 'StackPivot' exploit prevention by Sophos Endpoint Agent

Is there a browser hardening policy on your computer that might cause this (or an antivirus such as Sophos)?

Anyhow, I would like more info on your side. Leaving this discussion open so that other users may post their status.

[gf-amahoney]

Hey thanks for the follow-ups! Ah that issue you found may be very similar...

My leading candidate for the cause here may be a corporate cylance antivirus. Having it disabled I think prevents the issue from occurring. I'm not 100% certain due to the unreproducibleness, but maybe 90% sure.

I was hoping to do a bit more followup testing, maybe bisecting the modules being loaded to see if it's one in particular that triggers it.

Ah even this comment is similar here

Can reproduce. Different AV. Still not sure if it's an antivirus thing or not. Happens less frequently with devtools open.

One of my colleagues suggested this too that having devtools opened helped sometimes.