Constant reth::primitives::constants::MIN_PROTOCOL_BASE_FEE

pub const MIN_PROTOCOL_BASE_FEE: u64 = 7; // 7u64

The minimum tx fee below which the txpool will reject the transaction.

Configured to 7 WEI which is the lowest possible value of base fee under mainnet EIP-1559 parameters. BASE_FEE_MAX_CHANGE_DENOMINATOR https://eips.ethereum.org/EIPS/eip-1559 is 8, or 12.5%. Once the base fee has dropped to 7 WEI it cannot decrease further because 12.5% of 7 is less than 1.

Note that min base fee under different 1559 parameterizations may differ, but there’s no significant harm in leaving this setting as is.