Steps to reproduce:

1. Create a UI document
2. Open it in the UI Builder
3. Select the root element in the Hierarchy pane
4. In the inspector, check "Editor Extension Authoring"
5. In the toolbar of the viewport, change the theme to "Active Editor Theme"
6. Create a VisualElement and name it "V0"
7. Sets V0's position = absolute
8. Add a child VisualElement to V0 and named it "V1".
9. Sets V1's flex-direction = row, width = 200px and height = 100px
10. Add a child VisualElement to V1 and named it "V2".
11. Sets V2's align-self = flex-start and {}flex-grow=1{}.
12. Add a Label to V2 with some text and named it "V3"
13. Set the label's flex-grow=1
14. Verify the resolved height of V0, V1, V2, V3 using "Window/UI Toolkit/Debugger": 

Here are steps to use UIToolkit Debugger with the UI Builder:

1. In UIBuilder, click the Preview button on the toolbar of the viewport.
2. Open the UI Toolkit Debugger from ""Window/UI Toolkit/Debugger".
3. Select "Builder" in the Panel dropdown in the toolbar of the Debugger window.
4. Click the "Pick Element" button
5. Pick the element you want to inspect in the UIBuilder window.

Note: You can directly use the attached uxml file to save some time.

Actual results: 

The heights of V0, V1, {color:#de350b}V3{color} are around 100px whereas V2's height is around 15px/17px(font size)

Expected results: 

The heights of V0, V1 are around 100px whereas the height of V2 and {color:#de350b}V3{color} are around 15px/17px (font size)
8:28

Note that the expected results is based on what we should expect from html/css specs as the image below shows. However, before this regression, the actual result was not even the right one  neither but at least it was not causing the linked bug. In previous version, the result was : The heights of V0, V1, V2, V3 are all around 100px, which was not right neither.

!image-2025-06-13-08-44-50-343.png|width=444,height=410!

Reproducible with versions: 6

Not reproducible with versions: 

Can’t test with versions: 

Tested on (OS): 

Notes: