At the moment, ApplicationScopedContextualInstanceStrategy uses a synchronized block to serialize access. If a user's application-scoped bean constructor stupidly does lots of I/O work and other things that it really shouldn't do, when virtual threads are in use this can pin the carrier thread. It would be nice if this synchronized block were refactored to use Locks instead, which are virtual thread friendly. I have a PR ready to submit if this is a feature that someone would be interested in. I emailed weld-dev and heard nothing and the archives site seems to think that there are no messages for the month so I'm not sure what happened, so I'm filing this JIRA.