Authorization code with PKCE, a Sign in card in settings, and the echolot://auth
redirect handled next to the enrolment one - told apart by host, because one
spends a token and the other completes an authorization, and confusing them
would fail obscurely.
The detail that decides whether this survives a real phone: the PKCE verifier is
written to storage before the browser opens rather than held in memory. Handing
control to a browser backgrounds the process and Android may kill it, so the
callback arrives at a fresh one. An in-memory verifier works on a developer's
device and fails under memory pressure.
Pending state is cleared before the exchange is attempted, whatever the outcome:
it is single-use, and leaving it behind would let a later callback complete a
flow nobody started.
Also records an open issue the question about server requirements surfaced: two
probes hardcode the reference deployment, so a user with no server still sends
DNS and STUN traffic to fmr without being told. For a tool this careful about
what leaves the device, that is the wrong default.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
