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Thank you for taking the time to provide such a detailed report and for documenting the results of your Raycast and Karabiner-Elements testing. The results provide a useful distinction between a general keyboard redirection failure and a shortcut that is being handled locally before it can reach the remote Windows session.
Based on the behavior you described, the main issue appears to be a local macOS shortcut conflict rather than a failure of the remote Alt + Space shortcut itself.
Your Experiment C is particularly helpful. When Raycast is completely closed, Option + Space successfully reaches the remote Windows session and activates CmdPal. This indicates that Windows App can forward the shortcut when the key combination is not intercepted locally.
Apple documents that keyboard shortcuts can conflict between applications and may need to be changed when the same combination is already in use. In this scenario, because Raycast has registered Left Option + Space as a global shortcut, macOS/Raycast handles the combination locally before Windows App can use it for the remote session.
Microsoft's Windows App documentation also describes how keyboard input and certain key combinations are handled in remote sessions. However, the current documentation does not describe a configurable "capture all keyboard input" or "prioritize remote shortcuts over macOS global shortcuts" option for Windows App on macOS.
For that reason, your suggestion for a configurable keyboard-capture mode is a reasonable feature request and could improve the experience for users who frequently switch between macOS and Windows.
1. Karabiner-Elements behavior
The Karabiner-Elements behavior is worth treating as a separate issue.
Your observation that the Windows On-Screen Keyboard appears to release Alt when Space is pressed after the Karabiner remapping may indicate that the modifier key state is not reaching the remote Windows session as expected. However, the On-Screen Keyboard observation alone isn't enough to confirm that the problem is specifically within Windows App.
Because Karabiner-Elements changes the keyboard events before Windows App processes them, the issue could occur at different points in the input path:
Physical keyboard → macOS/Karabiner → Windows App → RDP keyboard redirection → Windows
If possible, it would be helpful to compare the following scenarios:
- Native Option + Space
- Karabiner-remapped Option + Space
- Left Option versus Right Option
- Scancode versus Unicode keyboard input mode, where available
- Windowed versus full-screen sessions
Capturing the Windows-side key-down and key-up events would also help determine whether Alt is actually being released before the Space event reaches Windows.
2. Conclusion
I would separate this report into two items:
- Feature request
Windows App for macOS currently does not document an option that gives the remote session exclusive or prioritized keyboard capture over conflicting macOS global shortcuts. Adding such an option, where permitted by macOS, could significantly improve the experience for users who rely on the same shortcuts across macOS and Windows.
- Potential compatibility issue
The modifier-key behavior observed with Karabiner-Elements deserves further investigation. At this stage, additional keyboard-event tracing would be needed to determine whether the modifier state is being changed by Karabiner-Elements, macOS, Windows App, or later in the remote input path.
For now, the most practical workaround would be to remove or change the conflicting Raycast shortcut. Your own testing shows that Option + Space is forwarded successfully and activates CmdPal once Raycast is no longer capturing the combination.
Moreover, I would recommend submitting the keyboard-capture behavior through the Windows App feedback channel as a feature request and including your Raycast and Karabiner-Elements reproduction steps. In particular, the difference between the behavior with Raycast enabled and the successful result after completely quitting Raycast provides useful diagnostic information.
References:
Use keyboard, mouse, touch, and pen in Windows App - Windows App | Microsoft Learn
Create keyboard shortcuts for apps on Mac - Apple Support (SG)
Mac keyboard shortcuts - Apple Support
Remap Keys and Shortcuts with PowerToys Keyboard Manager | Microsoft Learn
Compare Windows App features across platforms and devices - Windows App | Microsoft Learn
Keyboard Input Overview - Win32 apps | Microsoft Learn
Create keyboard shortcuts for apps on Mac - Apple Support (SG)
I hope this helps clarify the behavior and provides a useful direction for both the workaround and the feature request.
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