Expected ordering of callbacks for Websocket endpoint?

[Sboddd]

Are there expectations regarding the order of callbacks for a @ServerEndpoint? I've got a @ApplicationScoped @ServerEndpoint that has @OnOpen and @OnMessage methods. I was doing a bit of setup work in the OnOpen callback, storing the results in session.getUserProperties, and then attempting to get that value out in OnMessage, but this was periodically failing in OnMessage.
It appears that OnMessage can be invoked before OnOpen completes (easy enough to test - if you set a breakpoint in both methods, you can hit both breakpoints at the same time.) This was surprising to me - is this a bug in Quarkus, or is it expected for onMessage to be invoked before onOpen has completed?

Thanks!