(MAC user) Unable to open Onyx no longer

[threshprince30]

I used to be able to run Onyx but ran into an issue with "The application "FINDER" does not have permission to open "Null". I have followed the instructions to enter the prompt in TERMINAL but it says "Permission denied". Currently on 26.2 Tahoe

[masranber]

I ran into the same error on macOS Tahoe 26 and was able to narrow it down to a code signing issue affecting the app bundle.

Also I'll mention I saw the same behavior with several Onyx releases going back to 2023 which previously worked fine for me. That makes me suspect this is caused by a macOS security policy change in Tahoe.

On a completely fresh download gatekeeper reports:

spctl -a -vv Onyx.app
Onyx.app: invalid Info.plist (plist or signature have been modified)

codesign reports the same issue:

codesign --verify --deep --strict Onyx.app
Onyx.app: invalid Info.plist (plist or signature have been modified)
In architecture: x86_64

In my case removing the quarantine flag had no effect. I did however fix it by re-signing the app bundle.

Workaround

Re-sign the app bundle with codesign (built into macOS, you don't need to install anything):

codesign --force --deep --sign - Onyx.app

Optionally remove the quarantine flag to avoid the “could not verify the developer” prompt that requires manual approval in Settings -> Privacy and Security:

xattr -dr com.apple.quarantine Onyx.app

Now the app should open normally.