Fixed-Rate Lending
Fira enables fixed-rate borrowing through a lending market where BT serves as the loan token, giving borrowers predictable costs.
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Fira enables fixed-rate borrowing through a lending market where BT serves as the loan token, giving borrowers predictable costs.
Fira's fixed-rate lending allows borrowers to post collateral and borrow at a known, fixed rate. The mechanism works by using Bond Token (BT) as the loan token in a dedicated lending market. Since BT is redeemable for a known value at maturity, the borrowing cost is determined by the BT discount at the time of borrowing.
The fixed-rate lending market has no interest rate model (IRM = address(0)). The rate is implicit in the BT discount — the difference between the BT price at borrow time and its face value at maturity is the borrower's fixed cost.
The router's supplyAndBorrowSingleToken function handles the full flow in a single transaction:
Supply collateral — Collateral tokens (e.g., Pendle PT tokens) are deposited into the lending market
Borrow BT — BT is borrowed from the lending market (supplied by the LiquidityInjector)
Swap BT → FW — BT is swapped to FW via the Fira Market AMM
Redeem FW → USDC — FW is redeemed for the desired output token
The borrower receives USDC (or another token) and holds a fixed-rate debt position denominated in BT.
Pre-expiry: Input token → FW (mint) → BT (AMM swap) → repay lending market.
Post-expiry: Input token → FW (mint) → BT+CT (mint via CT contract) → repay with BT. CT is minted but has zero economic value post-expiry.
Fixed-rate markets currently support Pendle Principal Tokens (PT) as collateral:
PT-USDe (Ethena USDe, May 7 2026 expiry)
PT-sUSDe (Ethena sUSDe, May 7 2026 expiry)
PT-USDG (Paxos USDG, May 27 2026 expiry)
Positions that fall below the liquidation LTV (LLTV) can be liquidated. The liquidator repays part of the debt and receives collateral plus a liquidation incentive.
Predictable costs — Fixed rate determined at borrow time
Single-transaction flow — Collateral supply, BT borrow, swap, and redemption in one call
Whitelist-gated supply — Only the LiquidityInjector can supply BT to fixed-rate markets
Maturity grace period — 24-hour grace period after BT expiry before liquidations are enforced
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