Thanks, Matthew! That's exactly what it was. I fixed that and it worked fine, no fallbacks needed.

It's very possible that I misattributed the issue. I'll take another look at it. :) Thanks for helping me dig into it further!

I kept running in an issue where I could register a passkey with Apple Touch ID without any issues, but then the browser couldn't find my passkey. This seemed to solve that, but I bet there's a better approach.

Oh, great point! I hadn't considered multiple tabs. I'll update this.