Sources close to the couple tell us ... Cardi's returning to the Atlanta home they shared before the breakup. We're told this is the first time she's been back to stay there with Offset and Kulture since December ... when she ripped into her husband for allegedly cheating.

There have been numerous signs lately of a reunion. Cardi posted last week, "I wanna go home" -- but our sources say it's a done deal now, because Offset proved himself to his wife.

We're told one of the key factors was Offset changing his phone number, in order to show Cardi he's serious about being honest and faithful. Our sources say the new digits are strictly for Cardi and business calls.

More importantly, there's a new, "no groupies" rule, which will be in full effect this weekend. We're told Offset's not allowing any female fans near him during his Super Bowl appearances in ATL. He wants Cardi to know he's serious about their marriage.

The Rams and Patriots ain't the only ones with a lot to lose this weekend.