The on-again couple, who broke up at least twice in the last year, sparked reports of another reconciliation when they were seen flirting at the holiday party at Perry's home last week.
"They are just hanging out," one source told E! "They are not putting a label on it."
While the two have apparently been spending nights together, they haven't made a public appearance since their split in March, the entertainment news outlet said.
Notable deaths of 2014 [PHOTOS]