The Next.js admin UI is exported with trailingSlash: true, so the proxy
serves /ui/login at /ui/login/index.html and 308s /ui/login → /ui/login/.
The waitForURL predicate used endsWith("/ui/login"), which never matched
the canonicalized URL and timed out after 15s.
This was masked until the build artifacts were regenerated against the
AuthContext fix: the prior bundles still hit the racy redirect path that
fired before proxyBaseUrl was populated, producing /ui/login (no prefix,
no proxy round-trip, no trailing slash) which fortuitously satisfied the
predicate. The first PR to ship the corrected bundle exposed the
assertion bug.
Switch the predicate to includes("/ui/login"); the prefix assertion below
still validates the SERVER_ROOT_PATH preservation that is the actual
contract under test.
54ed5a4eb5