Hi @ksen0 and @dhowe, I'm trying to debug this error, below is what I did to reproduce it:

1. open the demo https://editor.p5js.org/davepagurek/sketches/9MJzIBMBW
2. remove the line debugger, add one line after the let font = await loadFont('https://fonts.googleapis.com/css2?family=Montserrat:ital,wght@0,100..900;1,100..900&display=swap', { sets: 'latin' }) to print the font console.log(font)
3. click the ▶️ button
4. wait......
5. the issue shows as above

In addition, I checked the repo and plan to add check for p5.Font at those two files, please correct me if I missed any other place:

1. https://github.com/processing/p5.js-web-editor/blob/develop/client/utils/previewEntry.js
2. https://github.com/processing/p5.js-web-editor/blob/develop/client/modules/IDE/hooks/useHandleMessageEvent.js

Expected Behavior

Do not try to stringify objects that are [expected to be] excessively large

If I understand this issue correctly, this issue is occurs only when logging the font object and not otherwise? In which case, I believe using local state to store the logs fixes this issue, since the 'stringify'ing takes place due to it being stored in a Redux state value (which uses Immer). Please correct me if I am wrong.

Relevant discussion: #3178 (comment)

Thank you all for providing new thoughts for this issue. I was a bit busy some time ago and didn't have time to update my previous PR and this issue. After my verification yesterday, the fix of #3424 has eliminated the error when the p5.Font type is printed by console.log(). This is because the problem in this issue is basically the same as #3178, and there is a circular reference in the object to be printed.
@dipamsen As you mentioned in previous comment, I submitted a new PR #3499 to utilize the React context. @raclim I hope we can make that PR as a start point and then refactor all related code pieces.