Priority support was added to QQs in 4.0 but up to (including) 4.2, they worked quite differently than in CQs:
Starting with 4.3, QQ priorities are more similar to how CQs implemented them (strict priority):
https://www.rabbitmq.com/blog/2026/04/23/rabbitmq-4.3-release#32-message-priorities
In either case, you don't set x-max-priority. - you just set the priority when publishing a message and that's it.
So, it sounds like the 4.3 behaviour is what you are looking for.
We could not introduce strict priorities earlier because Ra didn't support compaction. Not consuming lower priority messages would have led
to unbounded disk usage growth since we had to keep everything since the oldest unconsumed message. Starting with 4.3, Ra
can compact the segment files to only keep what is still needed (eg. lower priority messages without all the other ones).
Best,