UE 5.8.2 Editor never shows main window on macOS — UnrealEd_Layout_v1.6 tab spawn failure, survives full reinstall

General Issues and Bug Reporting (Unreal Engine)
1

Summary

On macOS, UnrealEditor 5.8.2 completes engine initialization but the main editor window never appears. The process stays alive in the background with zero visible windows. Reproduces on every project including a brand-new Blank/Blueprint project, and survives a complete uninstall + fresh reinstall of the engine.

Environment: macOS 26.5.2 (25F84), Apple M1 Max, UE 5.8.2-56702186+++UE5+Release-5.8. Reproduces with 0, 1, or 2 monitors attached.

Log:
LogSlate: The tab “Unknown” attempted to spawn in layout ‘UnrealEd_Layout_v1.6’ but failed for some reason. It will not be displayed.
LogSlate: Window ‘’ being destroyed
LogLoad: (Engine Initialization) Total time: XX.XX seconds

Steps to reproduce:

  1. Install UE 5.8.2 via Epic Games Launcher on macOS (Apple Silicon).
  2. Create a new Blank/Blueprint project, or open any existing 5.8 project.
  3. Editor initializes fully (asset registry scan completes, DDC maintenance runs) but no window ever appears.

Ruled out: not project/plugin-specific (fails on fresh Blank project), not EditorLayout.ini (fails identically deleted), not window position (NewWindowPosition corrected, no change), not multi-monitor/negative coordinates (fails with single monitor too), not a stale install (full uninstall + clean reinstall reproduces it identically on a brand-new project), not system-wide (UE 5.7.4 on the same Mac, same macOS build, opens and runs normally).

Expected: main editor window (Content Browser, Viewport, Outliner) appears after initialization, as in 5.7.4 on the same machine.
Actual: no window ever appears; process stays running invisibly until force-quit.

What Type of Bug are you experiencing?

Editor

Steps to Reproduce

  1. Install UE 5.8.2 via Epic Games Launcher on macOS (Apple Silicon).
  2. Create a new Blank/Blueprint project, or open any existing 5.8 project.
  3. Wait for engine initialization to finish (asset registry scan completes, DDC maintenance runs in the log).
  4. No editor window ever appears — the process stays running in the background with zero visible windows.

Expected Result

Steps to Reproduce:

  1. Install UE 5.8.2 via Epic Games Launcher on macOS (Apple Silicon).
  2. Create a new Blank/Blueprint project, or open any existing 5.8 project.
  3. Wait for engine initialization to finish (asset registry scan completes, DDC maintenance runs in the log).
  4. No editor window ever appears — the process stays running in the background with zero visible windows.

Expected behavior (What you think it should do):
The main editor window (Content Browser, Viewport, Outliner, etc.) should appear after initialization, exactly as it does with UE 5.7.4 on the same Mac (same macOS build, same hardware).

Observed Result

No editor window ever appears. The process stays running invisibly in the background (confirmed alive via ps/lsof) until force-quit. The log shows engine initialization completing, immediately followed by:

LogSlate: The tab “Unknown” attempted to spawn in layout ‘UnrealEd_Layout_v1.6’ but failed for some reason. It will not be displayed.
LogSlate: Window ‘’ being destroyed
LogLoad: (Engine Initialization) Total time: XX.XX seconds

Affects Versions

5.8

Platform(s)

Mac

Additional Notes

No crash dialog appears — the process runs silently with no window until force-quit. Full editor log available on request (XAVIMAC002Editor/XAVIMAC002.log, ~torder of magnitude of lines, includes the full plugin/module load sequence before the failure).

Related but non-matching reports checked before filing this: UE5.8 LogLayoutService warning on boot (Windows-only warning, not blocking) and MacOS: UE project loses screen/window (macOS window-visibility bug tied to monitor disconnects — different trigger, this reproduces with a single monitor and survives a clean reinstall).