Author: Diego Jiménez | DeFi Operations @ Odisea Labs | CFA L1
A Uniswap v4 hook that enables fixed-price swaps denominated in USDC, abstracting away gas cost volatility for institutional and retail users. Instead of paying unpredictable gas fees in ETH, users pay a flat fee (e.g., $2.99 on Mainnet, $0.99 on L2) regardless of network congestion.
The hook implements an individual savings/borrowing mechanism where users accumulate credits during low-gas periods and draw down during high-gas periods, effectively hedging their own gas cost exposure over time.
Live on Unichain Sepolia Testnet 🟢
- Hook Contract:
0xA24fEe104Fe00987AfC2714469159Cd3D8b840c0 - USDC Address:
0x31d0220469e10c4E71834a79b1f276d740d3768F - Verified: Yes ✅
- Explorer: View on Uniscan
In traditional finance, commodity costs (e.g., oil storage as % of barrels) are hedged using forward contracts to reduce variability for financial planning departments.
In DeFi:
- Gas fees are denominated in ETH (a volatile commodity)
- Network congestion causes fees to spike 10-100x during peak times
- Institutional treasury departments cannot forecast costs accurately
- CFOs require predictable operating expenses for budgeting
Example scenario:
Low congestion: Swap costs $0.50 in gas
High congestion: Same swap costs $30-50 in gas
Enterprises need fixed, predictable costs to justify DeFi integration.
Pricing:
- Mainnet (L1): $2.99 USDC per swap
- L2 (Base/Arbitrum/Unichain): $0.99 USDC per swap
Mechanism:
- Users pay a fixed USDC fee for every swap
- During low-gas periods: Surplus accumulates as "credits" in their account
- During high-gas periods: Credits are drawn down to subsidize excess costs
- Over time, users hedge their own gas exposure through temporal diversification
Combined with ERC-4337 Paymaster:
- Users sign transactions without needing ETH
- Paymaster executes transactions using pooled funds
- Users experience "zero gas" UX while maintaining cost predictability
┌─────────────────────────────────────────────────────┐
│ User │
│ Pays: Fixed $2.99 USDC (L1) or $0.99 (L2) │
└──────────────────┬──────────────────────────────────┘
│
▼
┌─────────────────────────────────────────────────────┐
│ USDC Fixed-Fee Hook │
│ • Tracks individual user balances │
│ • Accumulates credits (low gas periods) │
│ • Draws down credits (high gas periods) │
│ • Enforces credit limits based on lifetime contrib │
└──────────────────┬──────────────────────────────────┘
│
▼
┌─────────────────────────────────────────────────────┐
│ ERC-4337 Paymaster │
│ • Executes transactions on behalf of user │
│ • Pays gas in ETH from pooled treasury │
│ • Settles costs via hook accounting system │
└─────────────────────────────────────────────────────┘
mapping(address => int256) public userBalance; // Can go negative (borrowing)
mapping(address => uint256) public lifetimeContribution;
Credit limit = lifetimeContribution * 50% // Can borrow up to 50% of lifetime contributions (fees paid in USDC)Example flow:
| Swap # | Gas Cost | Fixed Fee | Surplus/Deficit | User Balance |
|---|---|---|---|---|
| 1 | $0.50 | $2.99 | +$2.49 | +$2.49 |
| 2 | $1.00 | $2.99 | +$1.99 | +$4.48 |
| 3 | $8.00 | $2.99 | -$5.01 | -$0.53 |
| 4 | $0.75 | $2.99 | +$2.24 | +$1.71 |
Average cost over 4 swaps: $2.99
Individual model advantages:
- ✅ No free-rider problem: Users only use what they've saved
- ✅ No bank-run risk: Your balance is yours
- ✅ Simpler governance: No pool management needed
- ✅ Better regulatory posture: Not pooling customer funds
- ✅ Fair attribution: Direct relationship between contribution and benefit
With credit limits:
- New users can borrow (up to 50% of lifetime contributions)
- Long-term users earn higher credit lines
- System remains solvent by design
beforeSwap: true // Collect fixed USDC fee
afterSwap: true // Calculate gas subsidy/charge
beforeSwapReturnDelta: false // NO modification of swap amounts (using transferFrom)
afterSwapReturnDelta: false // NO accounting only, no delta modificationfunction _afterSwap(...) internal override returns (bytes4, int128) {
// Estimate actual gas cost in USDC using Pool TWAP
uint256 actualGasCostUSDC = estimateGasCostTWAP();
int256 delta = int256(TARGET_FEE) - int256(actualGasCostUSDC);
if (delta > 0) {
// Surplus: User accumulates credits
userBalance[user] += delta;
lifetimeContribution[user] += delta;
} else {
// Deficit: User draws down credits
int256 deficit = -delta;
uint256 creditLimit = lifetimeContribution[user] / 2;
require(userBalance[user] >= -int256(creditLimit), "Credit limit exceeded");
userBalance[user] += delta;
}
return (BaseHook.afterSwap.selector, 0);
}- Predictable costs: Budget exactly for DeFi operations
- No ETH needed: Paymaster handles gas, users only pay USDC
- Self-hedging: Temporal diversification of gas exposure
- Stablecoin denomination: No ETH price exposure
- CFO-friendly: Fixed line item in OpEx budget
- Compliance: Easier to audit and report
- Planning: Can forecast DeFi costs quarterly/annually
- Risk management: Eliminates gas spike surprises
- Sustainable economics: Fee covers average gas + margin
- No adverse selection: Individual balances prevent gaming
- Scalable: Works for 10 users or 10,000 users
- Capital efficient: No need for massive reserve pools
Scenario: Hedge fund executes 500 swaps/month
Current Swaps:
- Gas costs: $25,000 - $75,000/month (highly variable)
- Budget uncertainty prevents allocation
With Fixed-Fee Hook:
- Gas costs: $1,495/month (500 × $2.99) on Mainnet
- Predictable, can allocate larger size
Scenario: User swaps weekly for DCA strategy
Traditional DeFi:
- Some weeks pay $2, some weeks pay $40
- Frustration during high-gas periods
With Fixed-Fee Hook:
- Always pays $0.99 (on L2)
- Builds credits during normal weeks
- Uses credits during congestion
Scenario: Monthly stablecoin transfers
Traditional DeFi:
- Unpredictable fees hurt low-income users
- Gas spikes make small transfers uneconomical
With Fixed-Fee Hook:
- Fixed $0.99 per transfer
- Budgetable for remittance services
- Design individual savings/borrowing model
- Implement hook with credit accounting
- Gas price estimation via Pool TWAP
- ERC-4337 Paymaster contract
- UserOperation validation logic
- Testing on testnet
- Frontend wallet integration (Privy)
- Deploy on Base (low gas, high throughput)
- Deploy on Arbitrum (established liquidity)
- Deploy on Unichain (native integration)
- Mainnet deployment (institutional focus)
- Deploy idle USDC to yield-bearing protocols
- AAVE for lending (3% APY on USDC)
- Circuit breakers for liquidity management
- Dynamic rebalancing based on utilization
- Risk management framework (max deployed %, withdraw limits)
- Tiered pricing (volume discounts)
- Corporate subscription plans
- Analytics dashboard for users
- Governance token for fee-sharing or voting on pricing
Deploying idle treasury USDC to AAVE for yield generation.
Assumptions:
- USDC APY on AAVE: 5%
- Gas costs for supply/withdraw operations
- Need to maintain minimum liquid balance for withdrawals
| Chain | Supply Gas | Withdraw Gas | Total Gas Cost | Min Balance (30d) | Min Balance (7d) | Min Balance (1d) |
|---|---|---|---|---|---|---|
| Mainnet | $15 | $22 | $37 | $8,880 | $38,000 | $266,400 |
| Base | $0.01 | $0.02 | $0.03 | $7 | $31 | $216 |
| Arbitrum | $0.01 | $0.03 | $0.04 | $10 | $41 | $288 |
| Unichain | $0.01 | $0.02 | $0.03 | $7 | $31 | $216 |
Interpretation:
- Mainnet: Only profitable if treasury > $50k and rebalancing weekly
- L2s: Profitable at almost any scale due to negligible gas costs
Strategy:
- L1: Keep 100% liquid until treasury > $500k
- L2: Deploy 70% to AAVE once treasury > $10k, keep 30% liquid
Fixed fee pricing is based on average gas consumption across typical swap scenarios.
| Operation | Gas Used | Notes |
|---|---|---|
| beforeSwap hook | 50,000 | USDC transfer + accounting |
| afterSwap hook | 80,000 | Gas calculation + balance update + TWAP calculation |
| Base swap (Uniswap v4) | 100,000 | Core routing logic |
| Total per swap | 230,000 | Approximate |
| Chain | Avg Gas Price | Low Congestion | High Congestion | Avg Cost per Swap |
|---|---|---|---|---|
| Mainnet | 30 gwei | 15 gwei ($0.50) | 150 gwei ($5.00) | $1.50 |
| Base | 0.005 gwei | 0.002 gwei ($0.001) | 0.02 gwei ($0.01) | $0.002 |
| Arbitrum | 0.01 gwei | 0.005 gwei ($0.002) | 0.05 gwei ($0.02) | $0.004 |
| Unichain | 0.003 gwei | 0.001 gwei ($0.0005) | 0.01 gwei ($0.005) | $0.001 |
ETH Price Assumption: $3,000
| Chain | Avg Gas Cost | Fixed Fee | Margin | Margin % |
|---|---|---|---|---|
| Mainnet | $1.50 | $2.99 | $1.49 | 99% |
| Base | $0.002 | $0.99 | $0.988 | 49,400% |
| Arbitrum | $0.004 | $0.99 | $0.986 | 24,650% |
| Unichain | $0.001 | $0.99 | $0.989 | 98,900% |
Notes:
- L1 pricing includes buffer for gas spikes (150 gwei scenarios)
- L2 pricing optimized for user acquisition (high margin but competitive)
- Revenue from margins can fund:
- Protocol development
- Insurance pool for extreme gas events
- Yield generation (reducing effective user costs)
| Parameter | Mainnet | L2s | Rationale |
|---|---|---|---|
| Max negative balance | $50 | $20 | Prevent single user from depleting treasury |
| Credit limit formula | 50% of lifetime contribution | 50% of lifetime contribution | Ensures users have "skin in the game" |
| Max subsidy per swap | $20 | $5 | Circuit breaker for extreme events |
| Parameter | Mainnet | L2s | Rationale |
|---|---|---|---|
| Min liquid treasury | 30% | 20% | Always maintain withdrawal capacity |
| Max deployed to AAVE | 70% | 80% | Reduce smart contract risk |
| Emergency mode threshold | Treasury < 10% of 30d avg | Treasury < 10% of 30d avg | Reduce subsidies during stress |
- Spread margin: Fixed fee - Average gas cost
- Yield on treasury: AAVE/Compound interest (Phase 3)
- Subscription tiers: Premium users pay monthly flat fee for unlimited swaps (Phase 4)
- Gas subsidies: High congestion periods
- Oracle costs: $0 (using internal TWAP)
- Infrastructure: Paymaster execution costs (if used)
- Development: Ongoing maintenance and upgrades
Mainnet (1000 swaps/month):
Revenue: 1000 × $2.99 = $2,990
Costs: 1000 × $1.50 = $1,500 (avg gas)
Oracle: $0
Dev: $0 (amortized)
Profit: $1,390/month (46% margin)
Base (10,000 swaps/month):
Revenue: 10,000 × $0.99 = $9,900
Costs: 10,000 × $0.002 = $20 (avg gas)
Oracle: $0
Dev: $0 (amortized)
Profit: $9,875/month (99.7% margin)
Additional yield (if $100k treasury @ 5% APY):
$100,000 × 0.05 / 12 = $417/month
Total: $10,292/month
MIT
For questions, partnerships, or enterprise integration:
- Email: diego@odisea.xyz
- Twitter: @Diegolden-com
- GitHub: github.com/Diegolden-com/usdc-fees-hook
Disclaimer: This is a design document. Smart contracts have not been audited. Use at your own risk. Gas cost estimates are approximations and may vary based on network conditions, ETH price, and contract optimizations.