The Counterfactual Guarantee

To understand how IRIS provides fixed rates on top of variable-rate venues, you need to understand the Solver Bond.

Solvers are profit-maximizing market makers whose economic interests are structurally aligned with borrower outcomes. They bear the risk that the ultimate underlying variable rates might spike higher than the fixed rate they guaranteed to the user. If this rate inversion occurs, the solver sustains a financial loss.

So how does the protocol cryptographically ensure they actually pay?

The Two-Tier Bond Architecture

Before a Solver can participate in the sealed-bid auction process, they must provision baseline capital into the protocol's BondManager contract.

1. Initial Lock (Maintenance Bond): When a Solver's quote wins a borrower's intent, the protocol mathematically calculates the worst-case negative carry for the exact duration of the specific loan. It then actively locks that portion of the Solver's deposited capital. This capital cannot be withdrawn or used to back other loans while the position remains open.
2. Idle Bond: Any excess un-locked capital the Solver has provisioned acts as a secondary, global buffer against catastrophic volatility across their entire portfolio of underwritten loans.

If variable rates exceed the fixed rate, the deficit comes directly out of the solver's own locked capital. A solver who systematically underestimates the risk premium or fails to execute spatial arbitrage experiences automatic bond slashing—an economically self-correcting mechanism. The smart contract acts as an impartial escrow, effectively guaranteeing the borrower's rate.

Shared Bond Capital (Solving Fragmentation)

In traditional fixed-rate automated market maker (AMM) protocols, every permutation of a lending market (e.g., Aave USDC, Compound USDC, Morpho WBTC) requires its own dedicated liquidity pool segregated by specific maturity dates. LPs must fragment their capital across dozens of shallow pools, leading to exorbitant slippage and terrible rates for borrowers.

IRIS inverts this architecture.

A solver provisions capital into a single, unified bond pool. The exact same bonded capital can simultaneously act as a counterfactual backing for loans executing across any venue, any asset pair, and any customized duration the solver algorithmically chooses to underwrite.

This is the power of the "counterfactual" guarantee: the capital exists as general-purpose commitment capacity until a specific signed intent crystallizes it into a locked liability. When a borrower's loan safely closes without default, the locked maintenance bond is instantly released back into the solver's global pool, ready to underwrite new positions.

Because Solvers can utilize and recycle their capital with maximum density, they require significantly lower profit margins. This architectural capital efficiency translates directly into substantially cheaper fixed rates for the end-user.