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Werk #20232: Fix icon selectors blanking out all icons after a failed save

Component Setup
Title Fix icon selectors blanking out all icons after a failed save
Date Jul 28, 2026
Level Trivial Change
Class Bug Fix
Compatibility Compatible - no manual interaction needed
Checkmk versions & editions
3.0.0b1
Not yet released
Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT
2.5.0p11
Not yet released
Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT
2.4.0p36
Not yet released
Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT

When a form contained an entry with a missing icon, saving it flagged the error - and blanked out the icons of all other entries as well.

This was most visible in Custom icons and actions (Setup > General > Global settings): with one entry whose icon was not set, pressing "Save" showed You need to select an icon. and rendered every entry of the list with an empty icon placeholder. As the icons were gone from the form, saving became impossible without picking every icon anew.

On top of that, opening an icon selector on a long list could fail with 414 Request-URI Too Long.

Technical background

After a failed validation, Checkmk re-renders the form from the submitted form data. The icon selector does read its value back from the request in that case, but the value was resolved to the empty icon before that fallback could kick in, so every widget lost its icon.

The 414 came from the back URL that the icon selector popup carries: it contained the complete request, including all form fields of the surrounding list. With many entries this exceeded the request line limit of the web server. The back URL now only carries the page context.

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