JRebel is fast on all Grails version, but requires a license per developer. I am not sure for Grails 4, but spent a ton time on this for the Grails 7 release and these solutions might help on 4: https://grails.apache.org/docs/7.0.7/guide/gettingStarted.html#developmentReloading

I tested the trial version of the JRebel solution, and it worked really well. I’ve reached out to them for a quote, but they’ve been slow to respond. Do you happen to know the cost of a license per developer? I need this information to present to my management team.

My contacts on the JRebel team at Perforce: Sam Wessel swessel@perforce.com Cell 612-205-5492 and Joseph Dryer jdryer02@perforce.com

I'm still investigating this issue and noticed something in the Grails source code. Specifically in

GrailsApp.groovy

, there is a section responsible for recompiling code when changes are detected. Could this be some kind of native hot reload mechanism provided by Grails? If so, why can't we rely on this for hot reloading instead of using a Java agent?

It helps, but Grails does not have hot reloading. It relied on springloaded for many years, but that ended with jdk 8.