SUMMARY Icon themes are not persistent after the end of the user session. STEPS TO REPRODUCE 1. Go to the Icons session in the Appearance tab in the System Settings 2. Install any icon theme from the "Get New" functionality 3. Apply the icon theme 4. Log out and log back in OBSERVED RESULT The icon theme resets back to the Breeze icons after logging out and logging back in. EXPECTED RESULT The icon theme is persistent after ending the user session. SOFTWARE/OS VERSIONS Operating System: KDE Linux 2025-08-10 KDE Plasma Version: 6.4.80 KDE Frameworks Version: 6.18.0 Qt Version: 6.9.1 Kernel Version: 6.15.9-arch1-1 (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen 5 5600 6-Core Processor Memory: 16 GiB of RAM (15.5 GiB usable) Graphics Processor: NVIDIA GeForce RTX 2060 ADDITIONAL INFORMATION
Actually, any type of third-party theming (icons, window decorations, colors, mouse cursor, etc) are not persistent. Widgets and panel layouts are.
SUMMARY Day-Night theme cycle functionality doesn't take into consideration user overrides STEPS TO REPRODUCE 1. Enable the automatic day-night theme cycle in the Quick Settings session in the System Settings 2. Go to the Icons session in the Appearance tab in the System Settings 3. Install any icon theme from the "Get New" functionality 4. Apply the icon theme 5. Log out and log back in OBSERVED RESULT After logging back in, the manually applied icon theme is no longer active. The system has reverted to the default icon theme for the current Global Theme (e.g., 'Breeze' for Light Mode or 'Breeze Dark' for Dark Mode). EXPECTED RESULT The user's selected icon theme should persist across logins and automatic theme transitions. SOFTWARE/OS VERSIONS Operating System: KDE Linux 2025-08-10 KDE Plasma Version: 6.4.80 KDE Frameworks Version: 6.18.0 Qt Version: 6.9.1 Kernel Version: 6.15.9-arch1-1 (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen 5 5600 6-Core Processor Memory: 16 GiB of RAM (15.5 GiB usable) Graphics Processor: NVIDIA GeForce RTX 2060 ADDITIONAL INFORMATION
This is currently an expected side-effect of the way the feature works. It switches between Global Themes, and Global Themes are allowed to change your icon theme. Most do, including the Breeze and Breeze Dark Global Themes. If you want to keep your icon theme, you need to find a Global Theme that includes it, and then set up that Global Theme to be one of the two that the system automatically switches between. In the future, a different implementation of this feature might allow switching only the color schemes, which should mostly have the same effect but allow you to keep your current icon theme, plasma theme, cursor theme, and so on. However a side effect of that would be that if you're using any icon themes or plasma themes them don't themselves respect the color scheme, the feature would seem broken. So there are challenges to doing it that way too.