How to reproduce:
- Open the attached “IN-150360-repro-deadlock” project
- Open the “HeavyScene”
- Close the Editor
- Make a file required by that scene unreadable, e.g. run "chmod 000" on the scene file (HeavyScene.unity)
- Open the attached project again
Actual result: The Editor freezes on the splash screen and a window titled "Opening file failed" is created but never painted or clickable, placed at the top-left corner of the display
Expected result: The Editor opens the project without freezing; the file-open failure is logged to the Console and startup continues (or aborts with a diagnosable error)
Reproducible with: 6000.3.0a2, 6000.3.24f1, 6000.6.1f1, 6000.7.0a6
Not reproducible with: 6000.0.0f1, 6000.0.83f1, 6000.3.0a1
Reproducible on: Ubuntu 24.04 LTS, Ubuntu 26.04 LTS (by user)
Not reproducible on: macOS 26.6 (M1), Windows 10 Pro
Workaround (according to user): Delete Library/LastSceneManagerSetup.txt before each launch and open the scene manually, so any open failure happens on the main thread where the dialog can be shown and answered. Unity recreates the file whenever a scene is opened, so this must be repeated before every launch