When I launch the JUCE 9.0.1 demo runner on macOS, it initialises my audio device to its lowest possible buffer size (in my case 16 samples). It used to initialise with a normal buffer size of 512 samples on JUCE 9.0.0
macOS 26.5 (25F71)
m1 machine
It happens both with an external device and my built-in MacBook Air Speakers