Seats are per person, credits are pooled, and clients never see your internals.
Invite from Team & client workspaces. They get an email link, set a password, and land in the workspace you invited them to.
Admin manages seats, billing and every workspace. Member plans and generates inside the workspaces they are given. Guest reads and comments only — no generation, no credits spent.
One balance for the whole team, with per-person usage visible on the team page. If someone is burning credits on regenerations, you will see it there before the invoice.