Two defects in the storage fallback, both reproduced:
The quota fallback repointed reads at sessionStorage through module state,
which a reload discards. The next page load probed localStorage, passed
the one-byte probe, tried to promote the pair and was refused on the same
quota, swallowed that, and read an empty localStorage: the identity sat one
store over, unreadable, and the guest re-registered. Reads are now
read-through: primary store first, sessionStorage second, promoting into
the primary only when it will take the pair and leaving it where it fits
when it will not. No module state has to remember which store won.
The migration wrote the token before the profile, so a store that accepted
the first write and refused the second left a token with no profile:
x-guest-token was sent while the provider prompted to register, producing
a second row with two live tokens. Every write is now profile-first and
rolls back on failure, so a store holds the whole pair or none of it.
Paul Nothaft
7a1ea842e4