Fluid Finance

Built: October 7, 2023

Fluid Finance is a pair of DeFi protocols on Flow: a lending & borrowing market where you deposit crypto as collateral and borrow against it, and a staking system where rewards pay out as redeemable option tokens instead of a plain drip of coins. Both lean on something most chains don't have: Cadence, Flow's smart contract language, treats your position as a first-class resource instead of a row in someone else's ledger, something that lives in your own account storage and can't be copied, only moved.

Lending & Borrowing (L&B)

Each user's collateral is a liquidityBucket resource, tracked by UUID rather than an address-keyed balance. Every supplyTokens / borrowTokens / unSupplyTokens call runs checkIfBucketIsUnderCollateralized against that specific bucket before it's allowed to complete: under-collateralized borrows and under-collateralized withdrawals both revert, not just get flagged.

An Administrator resource controls the global borrowLimitPerBucket plus a per-token supplyTokensLimit / borrowTokensLimit map, so which assets can be supplied or borrowed, and how much of the pool they can consume, is configurable per token rather than hardcoded.

Option Liquidity Mining (OLM)

Instead of emitting a plain reward token, staking here mints option tokens (a separate OptionToken.Minter resource issues them at a configurable rewardRate) that expire after timeToExpireOtokens and are redeemable for a distinct payout token via a PayoutToken vault. A stakeAccountingKey resource (handed to the staker) is what makes a given stake claimable or unstakable at all: lose it and you lose the claim, same resource-ownership model as the L&B buckets.

Sample flows

The README doubles as a runnable walkthrough: flow transactions send / flow scripts execute commands for both protocols end to end: create a bucket → supply → borrow → repay → unsupply for L&B, and stake → claim oTokens → redeem for payout → unstake for OLM.

Stack

Cadence smart contracts on Flow
Custom FungibleToken/NonFungibleToken/MetadataViews standard implementations under cadence/contracts/standards
Flow CLI (flow emulator, flow dev) for local development against the emulator