Hardware & OS:

MacBook Pro M3 (Apple Silicon)

macOS Sonoma (latest version)

Steam latest version

Problem Description:
I used to be able to play Spiral Knights on this MacBook as recently as August 3rd. Now, whenever I try to launch it from Steam, I get the following error:

OSError256
The application “Steam” does not have permission to open “(null)”.

The only option is to close the dialog with “OK.” No window prompts to authorize the game.

Steps Already Tried:

Verified game files in Steam.

Checked permissions on the Spiral Knights folder and Steam.app (chmod +x, recursive).

Removed macOS quarantine flags with xattr -dr com.apple.quarantine.

Installed Java (latest version) and verified via java -version.

Attempted to run any .jar file (none found; game is packaged as .app).

Tried to run Steam and the game with Rosetta enabled.

Observations:

The game worked fine before August 3rd.

macOS now blocks Steam from launching the game, giving “(null)” as the target.

Spiral Knights is packaged as .app; no .jar or separate Java launcher is exposed.

The problem persists even after fixing permissions, removing quarantine flags, installing Java, and running Steam under Rosetta.

Suspected Cause:

Incompatibility between Spiral Knights (Intel-based, Java-dependent) and Apple Silicon + macOS Sonoma.

Changes in Steam’s macOS launcher or macOS security policies may prevent the app from launching via Steam.

Request for Help:

Is there a known workaround for running Spiral Knights on Apple Silicon Macs?

Can anyone confirm if the game can still be launched via Steam on M1/M2/M3 Macs?

Are there any alternative methods to launch Spiral Knights outside of Steam while preserving saves and account connection?