Sources close to Blac Chyna tell TMZ ... she's NOT rekindling her flame with Jay, despite social media posts to the contrary. We're told the exes are keeping things strictly platonic this time around.

The rumor mill was spinning like crazy after pics and videos showed BC and YBN hanging together at Houston restaurant Turkey Leg Hut and a nightclub ... but we're told they bumped into each other at the eatery and went to the club as old pals.

Blac Chyna was in Houston for business, not to visit YBN ... and we're told after they danced the night away at the club, they went their separate ways. No after-hours hookups.

It's been over a year since BC and YBN broke up -- they dated for several months in 2018 -- and we're told Jay is now fully entrenched in the friend zone.

There's usually no coming back from that.