How it works
The vault
The vault is a program address on Solana with one token account for each of the eight tokens. Only the program can move tokens out of it, and only through a redeem.
| Token | Issuer | Backed by | Program |
|---|---|---|---|
 USDC | Circle | bank cash and T-bills | SPL Token |
 USDT | Tether | T-bills, gold, bitcoin, loans | SPL Token |
 USDG | Paxos | cash and T-bills | Token-2022 |
 syrupUSDC | Maple | overcollateralized loans paid in USDC | SPL Token |
 sUSDai | USD.AI | loans against GPUs | Token-2022 |
| PAXG | Paxos | gold bars in London vaults, one ounce per token | Token-2022 |
| XAUt0 | Tether | gold bars in Swiss vaults, one ounce per token | SPL Token |
| SPYx | Backed | shares of the SPDR S&P 500 ETF | Token-2022 |
Minting
- You pick a token and an amount.
- The program reads that token's live price and counts your deposit at the low side of its price band.
- It adds your deposit to the vault, then checks three things: the token's price is fresh (and, for a dollar, above $0.98), that token now holds at most its share of the vault (25% for a dollar or credit token, 15% for gold and SPYx), and the vault minus the worst single issuer failure still covers every REALS including the new ones.
- If all three hold, you get REALS for your deposit's value less 0.05%. If any fails, the whole transaction is undone.
Redeeming
You burn REALS and pick which token to take out. The program pays you that many dollars of the token, priced at the high side of its band, less 0.05%. Only the price of the token you take out has to be fresh.
Prices
The program reads seven price accounts and one pool directly on Solana:
Pyth for USDC, USDT and USDG, and for spot gold per ounce.- Chainlink for the exchange rates of syrupUSDC (in USDC) and sUSDai (in USDai), plus USDai's own dollar price.
- SPYx's own Raydium pool against USDC: the price now and its average over at least the last 15 minutes, taken between two of the pool's own records.
A Pyth price older than 5 minutes or a Chainlink price older than 15 minutes counts as missing. Each price becomes a band:
- A dollar token is never valued above $1 and never paid out as if worth less than $1. Pyth's confidence interval widens the band further.
- Gold is counted at spot less 0.5% coming in and paid at spot plus 0.5% going out, for the gap between a token and the metal.
- SPYx is counted at the lower of its pool price now and its 15-minute average coming in, and paid at the higher going out. A swap in the same transaction moves only the price now, so it cannot raise what a deposit is worth or what a redemption pays.
All of these lean against whoever is trading with the vault, so rounding and price noise end up in the buffer.
When a market is shut
Gold stops trading from Friday night to Sunday night. Over that time the vault keeps counting its gold at Friday's price, for up to four days, so minting and redeeming with every other token carries on. Gold itself waits: nobody puts gold in or takes it out until the price moves again.
SPYx works the same way when nobody has traded its pool for 30 minutes: its last average values the vault, and SPYx in and out waits for the next swap.
Fees
0.05% on every mint and every redeem. The fee is not sent anywhere: it stays in the vault and becomes buffer.