EIP-3198 — BASEFEE Opcode

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EIP-3198: BASEFEE Opcode

EIP-1559 added a base fee to blocks. EIP-3198 added the BASEFEE opcode (block.basefee in Solidity) so contracts can read the current block's base fee. Used by fee-aware contracts and on-chain MEV mitigation logic.

Neo Equivalent

The PolicyContract native is the equivalent: contracts read fee parameters via Policy.GetFeePerByte() and Policy.GetExecFeeFactor(). The fee model is deterministic per-block but doesn't auto-adjust; values change only when committee nodes vote a change.

Live on Neo TestNet

Both implementations are deployed on Neo N3 TestNet (network magic 894710606).

Implementation	Contract Hash	Deploy Tx
Solidity (neo-solc)	0x8ed358aea7789a0d2c60a42c692c469bf1da60a0	(reused — see 0x8ed358aea7789a0d2c60a42c692c469bf1da60a0)
Neo C# (nccs)	0x32b98cb268f39b8ced382e7fe6d160833ab4f630	(reused — see 0x32b98cb268f39b8ced382e7fe6d160833ab4f630)

Cross-implementation invocations match on getLastSeenFee. Source pairs under docs/standards-mirror/deployments/eip-3198/.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

contract FeeAware {
    /// @notice Estimate cost of a method given the current base fee.
    function estimateCost(uint256 expectedGasUsed) external view returns (uint256 wei_) {
        return expectedGasUsed * block.basefee;
    }

    /// @notice Refuse to operate if base fee is unreasonably high
    /// (e.g. avoid burning user funds during a gas spike).
    modifier reasonableBaseFee() {
        require(block.basefee < 200 gwei, "base fee too high");
        _;
    }
}

using System.Numerics;
using Neo;
using Neo.SmartContract.Framework;
using Neo.SmartContract.Framework.Attributes;
using Neo.SmartContract.Framework.Native;

namespace R3E.Examples;

[DisplayName("FeeAware")]
public class FeeAware : SmartContract
{
    /// <summary>Network fee per byte from the policy contract.</summary>
    public static long FeePerByte() => Policy.GetFeePerByte();

    /// <summary>Estimate the network fee for a transaction of given size.</summary>
    public static long EstimateNetworkFee(uint txSize)
        => txSize * Policy.GetFeePerByte();

    /// <summary>Multiplier applied to per-op system fees.</summary>
    public static uint ExecFeeFactor() => Policy.GetExecFeeFactor();
}