[ndm]

Are you triggering U2F challenges by visiting sites that support u2f? Opening the app doesn't do anything.

[lisper]

Yes. The configuration I was using (Yubico test site on Chrome) works against hardware tokens.

Just for context, I'm pretty well versed in U2F. I actually sell a U2F token of my own (https://sc4.us/hsm) and I've published a serverless U2F test harness (https://github.com/rongarret/u2f-test).