How can I quit Steam on macOS 10.12 without force quitting? Steam will not exit gracefully on macOS 10.12 Sierra. When selecting exit from the application menu or via secondary click on the app icon in the dock nothing happens. The process has to be terminated forcefully, and it will also stop the OS's poweroff process. On occasion the program will exit properly but I cannot see any pattern to it.

When running the application from the command line and then attempting to exit, at first nothing appears in the output, but after a minute or so the following is logged:

KQ: Error Unregistering write event KQ:Operation now in progress
Setting breakpad minidump AppID = 769
Steam_SetMinidumpSteamID:  Caching Steam ID:  76561198003850785 [API loaded no]


macOS Sierra 10.12.4, Steam API: v017, Steam package versions: 1490228413
I had this same issue. I lodged a ticket with steam support and they told me to enable beta client.

Here is a link about how to do just that that 

After signing up for beta it is now quitting for me and my double quits are gone. If you don't want to participate in the beta, hold on to your butts; a fix is probably coming soon when they get a stable beta.

-- I did say soon in my initial comment back on Apr 5 '17 so perhaps not so soon if you are here now.