Justin Bieber & Selena Gomez Hanging Out, All's Good With The Weeknd

Justin Bieber and Selena Gomez are back to spending time together -- most recently at her house with friends -- but don't make that leap yet ... she's still with The Weeknd.

We got pics of Selena walking into her Studio City pad Sunday evening... about 10 minutes after Justin arrived there in his white G-Wagon. Multiple sources tell us they also hung out once last week.

The get-together at her house was not a secret -- we're told they had mutual friends there too ... and The Weeknd was fully aware of it. The only reason he wasn't there is because he's on tour.

As for the exes -- we're told they were at the house with their pals until at least midnight ... and there was nothing romantic about it. They've been talking -- first reconnecting around the time Selena announced she'd undergone a kidney transplant ... but it's all copacetic.

Our Weeknd sources dispute there was any other face-to-face meeting besides Sunday ... but we're told the singer knows Selena remains friends with Justin.

Modern exes.