Repros on two Mac, running MacOS 26.0.1 (Tahoe), VS Code 1.104.2, Extension 4.1.7, Fusion 2604.1.25 arm64.
After selecting a program under "CNC Selector" with the post processor open, got notification "Post executable cannot be found. Please select your post executable."
Observing settings page, it looks like the auto post executable detection was not able to find it.
