Never mind, synchronous XHRs during beforeunload also causes crashes Safair. Async XHRs triggered during unload and before unload don't seem to actually fire causing a delayed disconnect on the server.

I'm not sure at the moment what to try next. According to some of the comments on the issue (https://github.com/SignalR/SignalR/issues/2650#issuecomment-29136539) hooking up an async XHR in addition to the preexisting synchronous XHR stops the crashes an presumably still fires the /abort request. 

hat would be super hacky, but really not too much different than what we do for Firefox >= 11 when withCredentials is used.

@davidfowl thoughts?