The /api/auth/register handler now branches on homeInstance:
- Local path (no homeInstance): gated by registrationOpen. When closed, a
valid inviteToken bypasses the gate and is consumed atomically inside
redeemInvite()'s transaction (user insert + usedCount bump + redemption
row all commit together, or all roll back). When open, inviteToken is
silently ignored.
- Federated path (homeInstance set): gated by federatedRegistrationOpen.
Token is ignored entirely on this path -- tokens never unlock federated
creation. Closed → 403 with "Federated registration is closed".
InviteUnavailableError thrown by redeemInvite() (concurrent revoke,
last-slot race, expiry between check-invite and submit) is mapped to 403
"Invalid or expired invite". The in-txn re-derive closes the TOCTOU window.
9 new tests cover the toggle matrix from spec §5.6 + invite consumption
semantics + federated-gate independence + last-slot race rejection.
Updates docs/systems/auth.md: rewrites the Registration Gate section to
describe the three-path model (open / invite / federated), adds the toggle
matrix, adds an Invite Tokens subsection with the atomic-redemption shape,
notes that the federated stub upgrade is always gated by
federatedRegistrationOpen, never by an invite token.
Jannis Braun
0559ea369b