Summary

Arma 3 fails to launch when installed on an external APFS volume whose volume name contains a non-ASCII character (Ø).

The exact same installation launches successfully when moved to the internal SSD.

System

• OS: macOS 26.6.2

• CPU/GPU: Apple M4 Pro

• Arma 3: current Public branch

• Mac version: Tested both the default Intel/Rosetta version and the experimental Apple Silicon native version

• External drive filesystem: APFS

• External volume name: PASSAGE-Ø

• Steam library: /Volumes/PASSAGE-Ø/SteamLibrary

Steps to reproduce

1. Install Arma 3 to a Steam Library located on the external APFS volume:
   /Volumes/PASSAGE-Ø/SteamLibrary

2. Launch either:

   • ArmA3.app (Intel/Rosetta)

   • ArmA3 AS Native.app (Apple Silicon native)

3. The game fails to launch.

4. Move the same Arma 3 installation to the internal SSD.

5. Launch the game again.

Expected result

Arma 3 should launch normally from an external APFS Steam library.

Actual result

When installed on the external volume, both the Intel/Rosetta and Apple Silicon native versions fail before the game starts.

The eON log reports:

Failed to open VPFS filesystem from file '/Volumes/PASSAGE-Ø/SteamLibrary/steamapps/common/Arma 3/arma3.vpfs'!

Relevant log:

[thread 00000001][I][1]: Detected 1 Metal devices
[thread 00000001][I][1]: Device 0: 'Apple M4 Pro'
[thread 00000001][I][1]: Using device 'Apple M4 Pro'
[thread 00000001][W][1]: ShaderCache11: Failed to open shader cache file ('/Users/diippii/Library/Application Support/com.vpltd.Arma3/eONprecompiledShaders.dat') to preload shaders! (2) No such file or directory
[thread ffffffff][I][1]: Metal cache precompilation thread: start
[thread 00000001][W][1]: AppendGameMappingsFromSDLGamepadConfigFile() - Could not open SDLGamepad.config !!
[thread 00000001][E][107]: Failed to open VPFS filesystem from file '/Volumes/PASSAGE-Ø/SteamLibrary/steamapps/common/Arma 3/arma3.vpfs'!
[thread 00000001][I][107]: ===enforcing log flush===

Additional testing

The arma3.vpfs file exists and is readable by macOS.

ls -lh reports:

-rwxr-xr-x@ ... 86M ... arma3.vpfs

The external volume is:

File System Personality: APFS
Media Read-Only: No
Volume Read-Only: No

Steam's Verify Integrity of Game Files reports that all files are valid.

A normal macOS file open succeeds on the exact same path:

OPEN OK: 3

using:

python3 -c 'import os; p="/Volumes/PASSAGE-Ø/SteamLibrary/steamapps/common/Arma 3/arma3.vpfs"; f=os.open(p, os.O_RDONLY); print("OPEN OK:", f); os.close(f)'

Reading the file directly with dd also succeeds.

The application bundle itself passes code-signature verification:

ArmA3.app: valid on disk
ArmA3.app: satisfies its Designated Requirement

The two executables are:

ArmA3.app
Mach-O 64-bit executable x86_64

and:

ArmA3 AS Native.app
Mach-O 64-bit executable arm64

Both versions exhibit the same VPFS error when run from the external volume.

Important A/B test

After moving the same game installation to the internal SSD, Arma 3 launches successfully.

Therefore, the game files themselves do not appear to be corrupt.

The difference appears to be the storage location/path.

Possible cause

I suspect this may be related specifically to the non-ASCII Ø character in the external volume name:

/Volumes/PASSAGE-Ø/

However, I have not changed the volume name, so I cannot yet determine whether the problem is:

1. the non-ASCII character in the path,

2. external-volume handling in the Mac port,

3. or an interaction between the two.

It would be useful to know whether the VPFS implementation has any known limitations with external volumes or non-ASCII paths.

Conclusion

The same Arma 3 installation:

• fails from an external APFS volume named PASSAGE-Ø

• succeeds from the internal SSD

• fails with both Intel/Rosetta and Apple Silicon native versions

• has a valid arma3.vpfs

• passes Steam file verification

• can be opened/read normally by macOS

This appears to be a reproducible Mac-port compatibility issue involving the game installation path/storage location.