Parametric options
A BlockFinaX event is an expiry-settled parametric FX option. This Stellar adaptation retains the existing range payoff, event-level pool, premium-rate choice, and three participant roles. Settlement determines the entitlement; claiming transfers the payout.
The payoff function
An upward event (a Cap) has a strike below its payout limit. The rate is quoted in the event's declared direction, for example local currency per USD. A rise in that quote can represent local currency weakening. A downward event (a Floor) mirrors the geometry.
| Upward fixing | Gross payout |
|---|---|
| At or below strike | Zero |
| Above strike and below the limit | Notional multiplied by the fixing minus strike, divided by initial rate |
| At or above the limit | Notional multiplied by the limit minus strike, divided by initial rate |
For a downward event, use the positive movement from strike toward the lower limit. initialRate remains the denominator, matching the existing product. payoutCap, the limit, is a price level, not an amount of USDC. The maximum liability is calculated from the notional and the strike-to-limit distance. Claim fees, where configured, are disclosed separately from gross payout.
Amounts use integer SAC base units; rates use the event's configured fixed-point scale. Checked multiplication and deterministic downward rounding avoid floats and overflow. The Stellar port must pass the same economic test vectors as the EVM range product before release.
The lifecycle
These are proposed Soroban entry-point names. The port must preserve fee and participant accounting semantics; it cannot silently introduce different entitlement rules. Event creation validates capacity, configuration, expiry, and account authorization. An unsettled event cannot release funds promised to hedgers.
Self priced and engine priced events
Underwriters retain the choice to set their own premium rate or use the existing pricing engine as a reference. Engine pricing does not become compulsory merely because the chain changes. If optional signed attestation is supported, its Stellar payload binds the network, contract, creator, exact terms, timestamp, and nonce. EVM EIP-712 bytes are not a Soroban signature. See premium pricing.