Severe performance regression on iOS 26 (WebKit 26) when rendering picture-elements with multiple PNG layers — works flawlessly on iOS 17

[iStump]

Since updating to iOS 26 / iPadOS 26, Home Assistant dashboards using picture-elements with multiple transparent PNG layers have become unusably slow on Safari and the HA Companion App.

The exact same dashboards work perfectly on iOS 17 (e.g., iPhone XS) and also on desktop browsers.

This appears to be a WebKit 26 GPU memory regression, not a Home Assistant frontend issue, because the problem only occurs on devices that use WebGPU as the default rendering backend.

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Affected devices
• iPad Pro M4 (iPadOS 26.0 / 26.1)
• iPhone Air (iOS 26.x)

All affected devices show:
• lag
• stuttering
• delayed layer rendering
• occasional “white flashes” or missing elements
• GPU process crash → MREExceptionAdvisoryLimitActive_com.apple.WebKit.GPU

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Works fine on
• iPhone XS – iOS 17 (WebGL backend)
→ smooth, instant loading
→ no lag, no GPU errors

This strongly suggests the issue is caused by WebKit 26 / WebGPU memory limits, not Home Assistant.

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Reproduction Steps
1. Create a picture-elements card with a background PNG and ~50–120 transparent PNG layers
(These are typical for 3D floorplan dashboards.)
2. Open the dashboard in Safari or HA Companion App on iOS 26.
3. Observe lag, jank, slow loading, or GPU crashes.
4. Open the same dashboard on iOS 17 → works perfectly.

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Additional Technical Notes
• WebKit 26 replaces WebGL with WebGPU, which imposes aggressive VRAM limits.
• Large PNG layers (100% width, full-screen) appear to exceed these limits quickly.
• Even a single 3D floorplan with ~50 images can trigger degraded performance.
• This is not a network or HA server issue (tested on HA Core/Supervised/HAOS).

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Expected Behavior
• Dashboards that ran smoothly on iOS 17 should run at least as well on iOS 26.
• A more graceful fallback (WebGL) or increased GPU memory budget is needed for complex dashboards.

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Actual Behavior
• Severe performance drop only on iOS 26 Safari / WKWebView
• GPU crashes (MREExceptionAdvisoryLimitActive)
• Missing layers, freezing UI, slow updates

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Conclusion

This is a critical compatibility issue between Home Assistant dashboards and iOS 26’s new WebKit/WebGPU limits.
Even though this regression originates in WebKit, it heavily impacts Home Assistant users with 3D floorplan dashboards, and may require consideration or mitigation on the HA frontend side.

I have also opened a direct ticket with Apple (via Feedback Assistant) regarding this WebKit 26 regression, but unfortunately there has been no progress so far.
It would be extremely helpful if more users experiencing the same issue could report it as well, so Apple can properly prioritize and address the problem.

Sorry, my English is not very good, but I am really frustrated about this bug because my dashboard was a lot of work to build and i hope somebody can help me.