Challenge 1: Sepolia Gas Cap Hell (16.7M limit)

The Bug:

Error: server returned an error response: error code -32000: 
transaction gas limit too high (cap: 16777216, tx: 25000000)

# Then when we lowered it:
Error: execution reverted: EvmError: OutOfGas (gas: 16711680)

# Foundry said "Deployed to: 0x..." but:
cast code 0xA487... --rpc-url $SEPOLIA_RPC_URL
# Returns: 0x (NO CODE!)

What Was Happening:

• Deploying

  YieldDonatingTokenizedStrategy

  implementation hit Sepolia's hard per-tx gas cap of 16,777,216
• Contract creation bytecode was too large even with optimizer enabled
• Foundry printed "Deployed to..." even when the tx reverted (misleading!)
• We tried 15.7M gas → OOG. Tried 16.7M → rejected by node. Tried 16.6M → OOG again.

How We Fixed It:

foundry.toml - AGGRESSIVE size reduction
[profile.default]
optimizer = true
optimizer_runs = 1          # Minimize runtime size
via_ir = false              # Reduce init complexity  
bytecode_hash = "none"      # Remove metadata
cbor_metadata = false       # Remove CBOR

# Force clean rebuild
forge clean && forge build -vvv

# Deploy just under cap with legacy tx
forge create YieldDonatingTokenizedStrategy \
  --gas-limit 0xFD0000 \  # 16,646,144 (under cap)
  --gas-price 2gwei \
  --legacy \              # Avoid EIP-1559 estimation quirks
  --broadcast -vvvv

VERIFY it actually exists:
cast code $IMPL --rpc-url $SEPOLIA_RPC_URL | wc -c  # > 2 = success!
cast call $IMPL "apiVersion()(string)"              # "1.0.0" ✅

Result: Successfully deployed implementation at

0xE668230D8F3289F9e252cA67Cc7dbEDaE9dB90E5

---

Challenge 2: USDC Supply Cap Full on Sepolia

The Bug:

Tried to deploy ATokenVault for USDC:
Error: call to non-contract address 0x2f39d218133AFaB8F2B819B1066c7E434Ad94E9e

Then when we used correct PoolAddressesProvider:
Deposits would fail with "supply cap reached" or liquidity issues

What Was Happening:

• Aave v3 Sepolia USDC market had supply cap limits
• Test USDC addresses on Sepolia were fragmented (multiple versions)
• PoolAddressesProvider address from mainnet docs doesn't exist on Sepolia

How We Fixed It - THE WETH PIVOT:

Switched to WETH (18 decimals, no supply cap issues)
export USDC_UNDERLYING=0xC558DBdd856501FCd9aaF1E62eae57A9F0629a3c  # WETH!
export AAVE_ADDRESSES_PROVIDER=0x012bAC54348C0E635dCAc9D5FB99f06F24136C9A  # Correct Sepolia

Deploy ATokenVault for WETH
forge script script/DeployVault.s.sol:DeployVault \
  --rpc-url $SEPOLIA_RPC_URL --broadcast -vv

SUCCESS:
ATokenVault (proxy): 0x6938238e57CBe1b4B51Eb3B51389cEf8d3a88521
ProxyAdmin: 0x119e5211b41f44362e6681e7EDF5fC07a46D7A4a
Factory: 0x86b0e29414501643320B05AfF836D699681E450e

Challenge 3: Permit2 Allowance Spender Confusion (Uniswap v4)

The Bug:

Swap reverted with custom error:
Error: custom error 0xe450d38c  # InsufficientAllowance-style error

Trace showed:
Currency0::transferFrom(deployer, PoolManager, 1e18)
└─ ← [Revert] custom error 0xe450d38c

What Was Happening:

• We granted Permit2 allowance to PoolManager as spender
• But the Router is the one that calls

  permit2.transferFrom()

  during settle
• Permit2 checks:

  allowance[user][token][spender]

  where spender = Router, not PoolManager!

How We Fixed It:

// script/03_Swap.s.sol - BEFORE (wrong):
permit2.approve(address(token0), address(poolManager), type(uint160).max, type(uint48).max);

// AFTER (correct):
// 1. Grant ERC20 approval to Permit2
token0.approve(address(permit2), type(uint256).max);

// 2. Grant Permit2 allowance with Router as spender
permit2.approve(address(token0), address(swapRouter), type(uint160).max, type(uint48).max);

// 3. Also keep direct ERC20 approval to Router (fallback)
token0.approve(address(swapRouter), type(uint256).max);

Result: Swap executed successfully, hook emitted

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