After spending a whole night troubleshooting, I finally realized that many people are experiencing the same issue. Steam won’t launch on macOS after the update, regardless of whether it’s an Apple Silicon or Intel Mac, and across macOS versions 12–15. The common symptom seems to be steamwebhelper is not responding, with the crash reason EXC_CRASH (SIGKILL (Code Signature Invalid)).

This appears to be a problem with Steam version 4.0. macOS 11 did not have this issue, but it shows the message: “On October 15th, 2025, Steam will officially stop supporting macOS version 11 (Big Sur)”, which is why I upgraded to macOS 12 and then to 13

I hope this issue can be resolved as soon as possible.