Hardfork.isBefore

import { Hardfork, LONDON } from 'tevm'

const fork = Hardfork(config.hardfork)

if (fork.isBefore(LONDON)) {
  // Use legacy transaction format (no EIP-1559)
  return {
    type: 0,
    gasPrice: calculateGasPrice()
  }
}

// Use EIP-1559 format
return {
  type: 2,
  maxFeePerGas,
  maxPriorityFeePerGas
}

import { Hardfork, SHANGHAI } from 'tevm'

function checkPUSH0Support(fork: BrandedHardfork) {
  if (fork.isBefore(SHANGHAI)) {
    console.warn("PUSH0 opcode not available before Shanghai")
    return false
  }
  return true
}

import { Hardfork, MERGE } from 'tevm'

function validateMiningConfig(fork: BrandedHardfork, config: MiningConfig) {
  if (!fork.isBefore(MERGE) && config.mining) {
    throw new Error("Mining not supported after Merge (Proof of Stake)")
  }
}

BERLIN (10) < LONDON (11) < MERGE (14) < SHANGHAI (15) < CANCUN (16)

import { LONDON } from 'tevm'

LONDON.isBefore(LONDON)  // false - not strictly before itself

import { LONDON, CANCUN } from 'tevm'

// Less than or equal
LONDON.lte(LONDON)           // true
!LONDON.isAfter(LONDON)      // true

// Strictly less than
LONDON.isBefore(LONDON)      // false
LONDON.isBefore(CANCUN)      // true