# Subscription currency and provider bound at purchase

Checkout lets the user choose currency per purchase (RUB via YooKassa, BYN via bePaid), but a Subscription permanently binds the currency and provider of its first successful payment, and every renewal charges that pair via its Saved Payment Method. Alternatives rejected: following the user's latest checkout currency (silently breaks auto-renew when it differs — a saved method cannot be charged in another currency or through another provider), and RUB-only subscriptions (excludes bePaid/ЕРИП customers). Topups remain freely per-checkout.

## Consequences

- BYN amounts are FX-derived (daily CBR RUB→BYN rate, cached) and frozen at invoice creation; renewals quoted early keep their quote.
- A user switching countries must let the current subscription expire (or be refunded) and repurchase in the other currency; no cross-currency migration in v1.