Merging Resident Cats with New Puppy

We've had our 5 1/2 moonth rescue pup Quesadilla for about 5 weeks now, and while things were going smoothly with our two resident cats, today felt like a bit of a setback. Quesadilla barked at Xena (female cat) twice—once when she jumped onto a new hallway shelf, and again when she approached me after Quesadilla's walk. The second time, Quesa even lunged a bit while barking (no chasing or contact). I corrected her immediately, and Xena recovered quickly, but I can tell she's a little spooked. Up until now, Quesa had been pretty wary of Xena, so this may be her testing boundaries now that she's feeling more confident. I’m trying to reframe this as part of the adjustment curve, not a failure—but it’s tough. Would love any advice or just solidarity from others who’ve been through this cat-dog integration phase.