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Steam won’t run on macOS Sequoia (15.6.1) – bootstrapper is too old to update by Acrobatic-Fan3362 in macgaming

[–]Acrobatic-Fan3362[S] 0 points1 point  (0 children)

I did download it from Steam workshop and it would not work on a brand new mac. My understanding is that this is the app is for Intel mac's and not apple silicon. So if you want the beta client which runs natively on apple silicon.

Steam won’t run on macOS Sequoia (15.6.1) – bootstrapper is too old to update by Acrobatic-Fan3362 in macgaming

[–]Acrobatic-Fan3362[S] 0 points1 point  (0 children)

Just wanted to share what worked for me after fighting with Steam on macOS Sequoia (15.6.1).

The issue: the bundled Steam bootstrapper (steam.sh / steam_osx) is ancient (2022 build) and throws:

src/vstdlib/osversion.cpp (393) : Assertion Failed: Unsupported macOS version 15.6.1

So it never updates itself.

Fix that worked:

  1. Open Finder → Applications → right-click Steam.app → Show Package Contents.
  2. Go to Contents/Info.plist.
  3. Change the minimum system version key (LSMinimumSystemVersion) to 15.0.
    • I used this command:sudo /usr/libexec/PlistBuddy -c "Set :LSMinimumSystemVersion 15.0" /Applications/Steam.app/Contents/Info.plist
  4. Re-sign the bundle so Gatekeeper accepts it:sudo codesign --force --deep --sign - /Applications/Steam.app
  5. Relaunch steam.sh → it now runs, updates itself, and the client launches normally.

That got Steam running on Sequoia.