Since upgrading to 1.20.5, Minecraft (Java) on macOS 14.4 has become virtually unplayable as the entire game "stutters". The game freezes (FPS goes from 30–50 down to 9) for about one second every 4 to 5 seconds.

This occurs with single player, server, and Realms-based games.

This occurs regardless of what action the player is taking: walking, mining, turning in place, or even just standing still. The F3 debug screen visibly stutters (freezes) then resumes, for example.

It occurs with no mods, no resource packs, and no other customizations; strictly a "vanilla" game.

Downgrading to 1.20.4 is an instant improvement with none of the issues described above.

UPDATE: testing on a newer iMac with an M3 CPU as well as an older MacBook Pro with an Intel CPU show no problems, so the issue seems to occur only with my Mac Studio thus far.

UPDATE: see the `F3+2` charts which show the massive red lag spikes reported by @cooldogwalter, @galaxy_flutter, and myself.