RWA·Ethereum · Fraxtal · Base · Arbitrum
Frax USD (frxUSD / sfrxUSD)
Frax's fiat-redeemable stablecoin and its yield-bearing wrapper. frxUSD is a 1:1, fully-collateralized USD stablecoin backed by permitted cash-equivalent reserves (BlackRock BUIDL, tokenized T-Bill funds, USDC). sfrxUSD is the ERC-4626 staked variant whose share price grows from a benchmark-rate strategy (carry trade, AMOs, IORB/T-Bill rate) — distinct from the older sFRAX (which streams yield against legacy FRAX).
- 01RWA-backed dollar with fiat redemption rail
- 02yield-bearing dollar (sfrxUSD) for savings UX
- 03treasury allocation needing benchmark-rate yield onchain
- 04Fraxtal-native settlement asset
- 05replacing legacy FRAX/sFRAX with the RWA-backed successor
- pnpm add viem
| Variable | Scope | Description |
|---|---|---|
| NEXT_PUBLIC_FRXUSD_ADDRESS | Client | frxUSD ERC-20 (Ethereum mainnet canonical address; mirror on Fraxtal/Base via canonical bridge). |
| NEXT_PUBLIC_SFRXUSD_ADDRESS | Client | sfrxUSD ERC-4626 (Ethereum mainnet: 0xcf62F905562626CFcDD2261162a51fd02Fc9c5b6). |
Use Frax USD as the RWA-backed dollar layer. To stake: `IERC20(frxUSD).approve(sfrxUSD, amount); IERC4626(sfrxUSD).deposit(amount, receiver)` — share price increases from the protocol's benchmark-rate strategy (carry trade / AMO / IORB), so `convertToAssets(shares)` gives the live frxUSD-equivalent. Redeem with `IERC4626(sfrxUSD).redeem(shares, receiver, owner)` — instant against the contract's liquidity buffer; large redemptions may need to wait for AMO unwinds. Mint/redeem of frxUSD against fiat is gated to whitelisted 'enshrined custodians' (BUIDL, T-bill fund operators) — retail users buy/sell on DEXs (Curve frxUSD pools) or via the Frax app's PSM, NOT directly from the issuance contract. NOTE: do not confuse frxUSD/sfrxUSD with the older FRAX/sFRAX — same protocol, different token, different backing model.
- ⚑frxUSD ≠ FRAX — they are different tokens with different backing. Legacy FRAX (algorithmic-then-collateralized) still exists; integrators must use the correct address per product.
- ⚑Direct mint/redeem is permissioned to enshrined custodians — retail flow is DEX-based; arbitrage maintains the peg but a custodian failure is the dominant tail risk.
- ⚑sfrxUSD APY is variable (alternates between IORB / T-Bill / carry / AMO) — never advertise a fixed rate; pull `convertToAssets(1e18)` or the published trailing-7d figure.
- ⚑RWA backing (BUIDL, tokenized T-Bills) inherits TradFi settlement risk — Friday-evening / weekend redemption requests may not settle until the next business day.
- ⚑Stablecoin de-pegs in 2023-2025 (USDC SVB, USDT brief de-peg) propagated into Frax via PSM USDC reserves — surface the current backing composition.
- ⚑Cross-chain frxUSD on Fraxtal/Base/Arbitrum uses canonical bridges (LayerZero / CCTP via FraxNet) — non-canonical wrapped variants exist on other DEXs and are NOT redeemable; check the address against the canonical list.
- ⚑Some jurisdictions (US persons in particular) have restricted access to the staking flow via the official front-end — geofence and surface the regulatory note.