sam-goldman / ArbSepoliaGasEstimation

Arbitrum Sepolia Gas Estimation Bug

The gas estimates in the broadcast files for Arbitrum Sepolia are significantly lower than the actual gas used. This doesn't break broadcasting with forge script, but it breaks off-chain tooling that uses forge script to estimate the gas without broadcasting the transactions.

To reproduce this bug, you'll need a funded private key on Arbitrum Sepolia. Here's a faucet.

Steps to reproduce:

1. git clone [e-mail]:sam-goldman/ArbSepoliaGasEstimation.git
2. cd ArbSepoliaGasEstimation
3. forge install
4. Run the following Forge script, replacing <your_private_key> with a funded private key on Arbitrum Sepolia:

PRIVATE_KEY=<your_private_key> forge script script/Counter.s.sol --rpc-url https://sepolia-rollup.arbitrum.io/rpc --broadcast

5. Open the broadcast file, which should be at broadcast/Counter.s.sol/421614/run-latest.json
6. Go to the transactions array, then go to the second element in the array, which corresponds to the counter.increment() call. You'll see that the "transaction.gas" field is 0x6af7, which is 27383 gas.
7. In the same file, go to the second element in the receipts array (i.e. the receipt that corresponds to the increment call). The gasUsed is 0xa98c, which is 43404 gas. This is ~1.5x the estimated gas of 27383.