Working as intended.

You can set up a second account using family share to share the games between them or you can set one or the other system to offline mode. Valve does not support one account doing this sadly.

引用自 ConceitedNobody：

PLEASE FIX: Why can't I play a game on my PC and someone on my steam deck play another game?

I'm opening COD on PC to play my son is playing a game on the steam deck. I have to refresh my sign in on pc and both games close on both devices.

This needs to be fixed ASAP

They should have their own account, use Steam Families for games that support sharing and both can play separate games online at the same time.

引用自 ConceitedNobody：

I'm opening COD on PC to play my son is playing a game on the steam deck. I have to refresh my sign in on pc and both games close on both devices.

This needs to be fixed ASAP

Actually, there is nothing to fix.

Imagine if that restriction wasn't in place. You could get a dozen people to pool their money and buy a game on one account, then they would all log into that account and play the game amongst the 12 of them, robbing the publisher of 11 additional sales.

One account = one person. It's been that way since the beginning.