It appears theres a 'stumpy booster' being assembled just outside the midbay.
— ∆lex ÐelderfiΞld 🎮🚀🟠 (@Alex_ADEdge) October 26, 2021
The unique attachment points added in the gridfin cutouts suggest this could be an in-development short-hop/tower-catch test vehicle.
📸 Thanks to @NicAnsuini & @BocaChicaGal #SpaceX #Starship #Elon pic.twitter.com/b53mHF31pm