I'm running an older MacBook Air with Sonoma and when I try to stretch a document across two screens it won't cross the border from one to the other. If I drag the document so that it crosses the two screens that's ok until I try to stretch it again and then it pops back to one screen. This never used to happen. Seems like a bug has worked its way into the OS.
MacBook Air 13″, macOS 14.8
This does sound like a macOS window-management issue rather than a hardware limitation.
You are running an older 13-inch MacBook Air with macOS Sonoma 14.8 (it is worth checking whether it has been updated to the latest Sonoma release, 14.8.8).
Since you mentioned that this behaviour used to work correctly and now windows snap back to a single display when resized, it suggests that a setting change or macOS update may have affected multi-display window handling.
1 - Try the following:
Check “Displays have separate Spaces”
Open Apple menu >> System Settings
Select Desktop & Dock
Scroll down to Mission Control
Turn off: “Displays have separate Spaces”
Log out of your Mac and log back in (or restart).
This is one of the most common causes of windows refusing to span across multiple displays. When this option is enabled, macOS manages each display more independently, which can prevent a window from being resized across both screens.
Apple documentation: Use multiple spaces on your Mac
2. Check Sonoma window tiling settings
macOS Sonoma introduced additional window management features that may affect manual resizing.
Open Apple menu >> System Settings
Select Desktop & Dock
Scroll to the Windows section
Try turning off options related to window tiling, such as: Drag windows to left or right edge of screen to tile,
Drag windows to menu bar to fill screen and Hold ⌥ key while dragging windows to tile (if available)
Apple documentation: Tile, arrange, and resize windows on Mac
3. Verify your display arrangement
Open Apple menu >> System Settings
Select Displays
Choose Arrange
Confirm that the displays are positioned correctly.
If one display is much higher or lower than the other, macOS may make it difficult to drag or resize a window smoothly across the boundary.
Apple documentation: Connect one or more external displays with your Mac
4. Test whether the issue affects all applications
Try resizing a basic Apple application such as: Finder, TextEdit or Preview
If those windows can span both screens but another application cannot, the issue is likely specific to that application.
If every application snaps back to one display, the problem is more likely related to macOS window management.
5. Restart the macOS WindowServer process
Sometimes the display/window manager can get into an unusual state.
Open Terminal
Your screens will briefly go black and return. This restarts the macOS window manager without requiring a full reboot.
Because this worked before and changed after an update, I would start with Step 1 (“Displays have separate Spaces”) and Step 2 (Sonoma window tiling settings).
If those settings are already correct, the issue may be a Sonoma window-management regression rather than a limitation of your MacBook Air.
If you can provide your exact display setup (for example: MacBook screen + one external monitor, two external monitors through a dock, or a specific adapter), that can help narrow down the cause.
This does sound like a macOS window-management issue rather than a hardware limitation.
You are running an older 13-inch MacBook Air with macOS Sonoma 14.8 (it is worth checking whether it has been updated to the latest Sonoma release, 14.8.8).
Since you mentioned that this behaviour used to work correctly and now windows snap back to a single display when resized, it suggests that a setting change or macOS update may have affected multi-display window handling.
1 - Try the following:
Check “Displays have separate Spaces”
Open Apple menu >> System Settings
Select Desktop & Dock
Scroll down to Mission Control
Turn off: “Displays have separate Spaces”
Log out of your Mac and log back in (or restart).
This is one of the most common causes of windows refusing to span across multiple displays. When this option is enabled, macOS manages each display more independently, which can prevent a window from being resized across both screens.
Apple documentation: Use multiple spaces on your Mac
2. Check Sonoma window tiling settings
macOS Sonoma introduced additional window management features that may affect manual resizing.
Open Apple menu >> System Settings
Select Desktop & Dock
Scroll to the Windows section
Try turning off options related to window tiling, such as: Drag windows to left or right edge of screen to tile,
Drag windows to menu bar to fill screen and Hold ⌥ key while dragging windows to tile (if available)
Apple documentation: Tile, arrange, and resize windows on Mac
3. Verify your display arrangement
Open Apple menu >> System Settings
Select Displays
Choose Arrange
Confirm that the displays are positioned correctly.
If one display is much higher or lower than the other, macOS may make it difficult to drag or resize a window smoothly across the boundary.
Apple documentation: Connect one or more external displays with your Mac
4. Test whether the issue affects all applications
Try resizing a basic Apple application such as: Finder, TextEdit or Preview
If those windows can span both screens but another application cannot, the issue is likely specific to that application.
If every application snaps back to one display, the problem is more likely related to macOS window management.
5. Restart the macOS WindowServer process
Sometimes the display/window manager can get into an unusual state.
Open Terminal
Your screens will briefly go black and return. This restarts the macOS window manager without requiring a full reboot.
Because this worked before and changed after an update, I would start with Step 1 (“Displays have separate Spaces”) and Step 2 (Sonoma window tiling settings).
If those settings are already correct, the issue may be a Sonoma window-management regression rather than a limitation of your MacBook Air.
If you can provide your exact display setup (for example: MacBook screen + one external monitor, two external monitors through a dock, or a specific adapter), that can help narrow down the cause.
have you tried to restart the Mac to see if the issues persist?
if so you might want to give this to apple as feedback, please do so using this link
Sonoma MacBook Air: Can't stretch windows across two screens
