Is it safe to have two separate circuits hooked to the same outlet?
Sounds like they messed up and accidentally made a &quot;ring circuit&quot;.
It's possible to have 2 circuits legally on one receptacle (the 2 sockets and frame called a &quot;yoke&quot;).  However, if you do have 2 circuits on a yoke, the breakers MUST be handle-tied with a factory provided handle-tie.
Otherwise a maintainer could plug in a radio and shut off circuits until the radio goes silent, then pull it out and get nailed by the other circuit.
A 2-pole breaker (that's a 2-pole NOT a duplex/twin/tandem) will also satisfy the requirement since its handles are tied.  They're a lot easier to obtain than handle ties.
Generally, handle-tying implies that they will be on opposite poles of 240V service (i.e. 240V between the different hots).  This is one of the very few cases where a handle-tie on a tandem would be alright, but they don't make any such thing, not least because it would be bad in any other application.