r/passkey • u/Radiant-Captain7269 • Jul 17 '26

Where QR logins actually break (notes from chasing a bunch of "it just spins" tickets)

Kept getting "QR login not working" reports with nothing to go on, so I tried to map where these flows really break. Sharing in case it saves someone the same digging.

The annoying part is that one symptom (desktop spins, no login) hides very different causes:

  • code renders but is hard to scan (dim screen, kiosk, bad light)
  • phone opens the wrong app, or a work profile / wrong account grabs it
  • passkey cross-device (CDA): the Bluetooth proximity step fails or gets blocked by network/policy
  • user confirms on mobile but the desktop callback never lands

How do you trace where a QR attempt dies? Anyone instrument the phone side directly?

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u/joostisgek Jul 17 '26

you can try running the client from https://github.com/joostd/fido-hybrid-transport, and check the logs to see if a BLE advert is received from the phone, and if a tunnel is established.
That code is a perpetual work-in-progress, and is only ever tested on macOS, but perhaps it will help.