Fix frontend settings reset by preserving WebView cache across scene lifecycle

[binarylogic]

Summary

Closes #3862

Fixes the long-standing issue where user frontend settings (dashboard selection, theme, sidebar configuration, timezone) periodically reset as if the app were freshly installed. This has been reported for years across iPhone, iPad, and Mac apps.

Root Cause: The app was aggressively clearing WebView cache on every scene disconnect via clearCachedControllers() in sceneDidDisconnect. Scene disconnects happen frequently during normal app lifecycle (backgrounding, multitasking, memory pressure), causing WebView recreation and loss of frontend settings stored in WebKit localStorage/IndexedDB.

Fix: Remove the unnecessary clearCachedControllers() call from scene disconnect while preserving appropriate cleanup during logout/error states via the existing onboarding observer.

Context: I'm a software engineer (Rust/Go/Ruby) but not an iOS developer. I used Claude to investigate the codebase and identify this root cause after experiencing the bug myself on multiple devices running internal-URL-only configurations.

Screenshots

N/A - Internal bug fix with no UI changes

Link to pull request in Documentation repository

Documentation: home-assistant/companion.home-assistant#N/A

Any other notes

This is a focused, surgical fix that:

• Preserves WebView state during normal app lifecycle
• Maintains proper cleanup on logout/error (unchanged)
• Adds protective comment to prevent regression
• Addresses community reports spanning multiple years and device types

The fix is conservative and low-risk - it only removes an overly aggressive cache clearing operation while leaving all legitimate cleanup paths intact.

[home-assistant]

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[home-assistant]

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[Copilot]

Pull Request Overview

Fixes the long-standing issue where user frontend settings (dashboard selection, theme, sidebar configuration, timezone) periodically reset by preventing aggressive WebView cache clearing during normal app lifecycle events.

• Removes unnecessary clearCachedControllers() call from scene disconnect handler
• Preserves WebView state during backgrounding, multitasking, and memory pressure events
• Maintains proper cleanup during logout/error states via existing onboarding observer

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Stale

[bgoncal]

Cleaning cached controllers doesn't mean cleaning the webview cache, if that was the case then force closing the app would also clean the cache as the controller would be deallocated.

[bgoncal]

Feel free to reopen the PR in case I misunderstood your change or you add a different approach.

[binarylogic]

@bgoncal Thanks for checking this out. This issue only occurs in the iOS app, never in the browser. When I access Home Assistant through a browser, my settings persist correctly. That makes me think this is specific to the iOS app rather than the frontend. If that’s not the case, could you point me to where I should look next?

[bgoncal]

When I saw your PR I forwarded the issue to frontend devs and requested priority in moving this settings to be persisted out of the browser (webview) domain, they will give priority to this.

[Uncloak2]

When I saw your PR I forwarded the issue to frontend devs and requested priority in moving this settings to be persisted out of the browser (webview) domain, they will give priority to this.

is there a github issue for it?

[bgoncal]

There is a PR open already home-assistant/frontend#25702