In my webapp I replaced my trinidad jars with newer version while Idea is running. Idea seemed to pick up the changes but all tags that are defined defined in the jars were shown completey in red in the editor. I checked that the definitions were still available in trinidad-impl-1.0.3-SNAPSHOT/META-INF\tr.tld resp. tr.taglib.xml (I am using facelets). Tried to restart Idea, but no luck. Finally I closed Idea, deleted "systems" folder, restarted and browsed my favorite web sites while Idea was re-parsing all files. When finished all my *.xhtmls files looked good again. I did this often with previous EAP builds (because I implemented patches to trinidad for my app) without any problem.