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Trading Options

Sell orders live on-chain at the FixedPriceSell contract. Buyers browse, pick a strike, and purchase directly. The seller's key can always cancel. Partial fills create successor boxes automatically.

Seller Flow

Listing for Sale

You choose how many tokens to list, pick a stablecoin (USE or SigUSD), and set your premium price per token. The Black-Scholes model suggests a fair price based on current volatility — you can accept it or override it.

What You See
1
Click “List for Sale” on your portfolio
2
Set premium (e.g. 0.18 USE per token)
3
Choose payment currency (USE or SigUSD)
4
Sign in Nautilus
5
Tokens appear under “My Sell Orders”
Screenshot: List for Sale modal
SELLER WALLET3 option tokensfrom writing stepready to listSIGN & LISTSELL ORDER BOX3 option tokens for saleR4: seller SigmaPropR5: [premium, feeRate, txFee]R6: dApp fee ErgoTreeFixedPriceSell
On-chain detailR4 = seller's SigmaProp, R5 = [premiumPerToken, dAppFeePer1000, txFee], R6 = dApp fee ErgoTree. The contract has two guards: the buy path (validates payment) and the seller's SigmaProp (can always cancel with no restrictions).
Buyer Flow

Buying an Option

A buyer browses the option chain, sees available contracts with premiums, and clicks “Confirm Purchase.” The buyer's stablecoin goes to the seller. The option tokens go to the buyer. If there's a dApp fee configured, a small cut goes to the fee address.

What You See (as buyer)
1
Navigate to the asset's trade page (e.g. ADA/USD)
2
Click a strike row to open the trade panel
3
See: available contracts, premium, “If Exercised” breakdown
4
Set quantity, click “Confirm Purchase”
5
Sign in Nautilus
6
Option tokens appear in your portfolio
Screenshot: Option chain + trade panel
SELL ORDER3 tokens @ 0.18 USE eachFixedPriceSell contractoption tokensBUYERreceives 3 option tokensready to exercise or holdstablecoinSELLERreceives 0.54 USE (3 × 0.18)optional feeDAPP FEEif configured (dAppFeePer1000)
On-chain detailThe contract computes tokensSold = inputTokens − outputTokens, then requires the seller to receive tokensSold × premiumPerToken − uiFee in the correct stablecoin. Partial fills are supported — the successor sell box preserves R4–R6 parameters.
Partial Fills

Buy Less Than Listed

If a buyer takes fewer tokens than listed, the contract automatically creates a successor sell box with the remaining tokens. The successor preserves the original pricing parameters (R4–R6), so the listing stays active at the same price. No action required from the seller — the contract handles it.

Key Takeaway

Sell orders live on-chain at the FixedPriceSell contract. The seller's key can always cancel. Partial fills create successor boxes automatically.

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