“ArgumentException” error and memory leak warnings are thrown when creating a new Sub Scene with a long name and Hierarchy V2 enabled

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Install the Entities package (com.unity.entities)
3. Make sure Hierarchy V2 is enabled (Unity > Settings > General > Use new Hierarchy window)
4. Create a new Sub Scene with a long name "New Sub SceneNew Sub SceneNew Sub SceneNew Sub SceneNew Sub SceneNew Sub SceneNew Sub SceneNew Sub Scene" in the Hierarchy window
5. Observe the Console window

Actual results: “ArgumentException” error and memory leak warnings are thrown

Expected results: No errors or warnings are thrown

Reproducible with versions: 6000.5.0a8, 6000.5.0b2, 6000.6.0a2

Not reproducible with versions: 6000.0.72f1, 6000.3.12f1, 6000.4.1f1, 6000.5.0a7

Tested on (OS): MacOS Silicon Tahoe 26.3, Windows 11

Notes:

• Requires Hierarchy V2 enabled