I'm having the same problem

Same, I keep getting the error message "This version of 'Steam' is not compatible with macOS 14 or later and needs to be updated. Contact the app developer for more information." No matter how many times I uninstall and download the latest version of Steam.

Same problem here..
Like OP I tried running steam_osx in the terminal and got the following output:
Looks like macOS Sonoma is not officially supported. Seems like a huge oversight to me if that's the case.

.

Did anyone ever come to a solution for this? This just started happening for me on 14.4.1 Sonoma.

Edit: For me, I've uninstalled the app (and the folder in application support) and reinstalled from a fresh download straight from Steam at least 10 times. Each time trying to run the application it just bounces a couple of times and then stops, I go into the package contents and try to run the `steam_osx` file manually and this is what I see:
```
/Applications/Steam.app/Contents/MacOS/steam_osx ; exit;
➜ ~ /Applications/Steam.app/Contents/MacOS/steam_osx ; exit;
src/vstdlib/osversion.cpp (393) : Assertion Failed: Unsupported macOS version 14.4.1
src/vstdlib/osversion.cpp (393) : Assertion Failed: Unsupported macOS version 14.4.1
src/steamexe/steamglobalinstance.cpp (389) : m_NamedPipe >= 0
src/steamexe/steamglobalinstance.cpp (389) : m_NamedPipe >= 0
[2024-04-01 11:46:41] Startup - updater built Mar 15 2022 17:15:24
[1] 19513 terminated /Applications/Steam.app/Contents/MacOS/steam_osx

Saving session...completed.

[Process completed]
```

Both Steam & SteamLink worked fine on my Macbook Pro for several months until recently (last couple of weeks).

it happened on me as well

how to fix ?

It appears mine was being blocked by an anti virus. Hope this helps!

I can't even get it to install it just hangs when I run it in a terminal all I get is
assertion failed: Unsupported macOS version14.5.0
bad cpu type in executable
logout

I've probably removed this app and tried to install it 50 times, it used to just start and then disappear now it just hangs bounces and does nothing I can't figure this out and I've searched through every help I could find

Same issue. I can download and install it, but it won't open. MacOS Sonoma 14.5. Any ideas to get it running?

Having issues as well on Sonoma 14.4.1 Message that I keep getting when I try to play Civ IV from my Library "Your current macOS version is unable to run 32-bit games. This game may not run."

Any ideas? I don't know what a 32 bit game is.

I'm having this problem with macOS 14.6.1. Steam won't start anymore, it instantly closes/crashes.

I have the same issue. Is there a timeline of when it will be updated/fixed?