Cassie's had a change of heart -- she's back with Diddy ... despite a domestic incident last week in which cops were called.
We broke the story ... Cassie dumped Diddy and a heated argument ensued. Diddy allegedly grabbed Cassie's phone, jumped out of the car they were in and skedaddled.
The Beverly Hills police investigated the incident and determined it was just one of those things and no crime was committed. Diddy gave the phone back and there was no violence, so it came down to a case of no harm, no foul.
Even if the cops saw it differently, Cassie made it clear she didn't want her boo prosecuted so it would have been dropped anyway.