False CLS Warnings in PSI Mobile Reports Despite Zero CLS in DevTools

### FAQ

- [x] Yes, my issue is not about [variability](https://github.com/GoogleChrome/lighthouse/blob/main/docs/variability.md) or [throttling](https://github.com/GoogleChrome/lighthouse/blob/main/docs/throttling.md).
- [x] Yes, my issue is not about a specific accessibility audit (file with [axe-core](https://github.com/dequelabs/axe-core) instead).
- [x] Yes, my issue is not answered by [other FAQs](https://github.com/GoogleChrome/lighthouse#faq).

### URL

https://www.justtravelingthru.com/rouen_france.php

### What happened?

On multiple pages using Bootstrap 5.3 and fully responsive images, PSI’s mobile report continues to flag non-zero CLS values even when:

width, height, and aspect-ratio are correctly set

fetchpriority="high" and loading="eager" are used

Chrome DevTools Performance recordings confirm CLS = 0

Desktop PSI reports CLS = 0

This pattern is becoming common across multiple destinations in our travel blog. We regenerate responsive image variants (640w, 1024w, full), maintain consistent aspect ratios, and wrap banners in stable div containers — yet PSI often flags CLS on mobile only.

This appears to be a Lighthouse simulation artifact, not real-world behavior.

Please advise or consider revising PSI’s CLS simulation thresholds to reduce these false positives.

### What did you expect?

PSI for MOBILE CLS should have been zero as was seen in Chrome DevTools

### What have you tried?

_No response_

### How were you running Lighthouse?

PageSpeed Insights

### Lighthouse Version

version 12.0

### Chrome Version

Version 136.0.7103.114 (Official Build) (64-bit)

### Node Version

_No response_

### OS

Windows

### Relevant log output

```sh

```