Finally some concrete proof that Chris Brown and Rihanna are communicating again: He wished her a Happy Birthday on Twitter!

Right around midnight last night, Brown took to his Twitter to write "HAPPY BIRTHDAY ROBYN!" -- Robyn Fenty being Rihanna's real name. 

It wasn't long after that the birthday girl, who was physically assaulted by Chris in 2009, responded "Thanks!" and re-tweeted the message. 

While Chris attended the singer's b-day bash last week, there was no evidence of them partying together because his people slapped anyone holding a camera with a confidentiality agreement.

The birthday message comes as rumors continue to swirl about the two collaborating on a remix for one of their new singles ... though neither has confirmed the story yet.

 Rihanna turns 24 today.

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