Opening the dev stack on a LAN address or a proxied hostname serves the
SSR HTML but never hydrates: Next.js answers /_next/*, /__nextjs_font/*,
and HMR with 403 for any host it was not started on. The page renders, so
it looks up — but no client handler is attached, and the login form's
onSubmit never fires. It reads as "login is broken" rather than as an
asset problem, and the only clue is a warning in the dev-server log.
Wire Next's allowedDevOrigins to a new DEER_FLOW_DEV_ALLOWED_ORIGINS env
var. Unset by default, so the localhost-only default is unchanged; it is
also dev-only, as Next ignores allowedDevOrigins in production builds.
Entries are reduced to the bare host that allowedDevOrigins matches
against, since an entry pasted from the address bar as
"http://192.168.1.10:2026" would otherwise match nothing and leave the
operator with the same 403 they were trying to fix.
Reported in #54 and #203.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
