Hardfork

import { Hardfork } from 'tevm';

const fork = Hardfork("cancun");
if (Hardfork.hasEIP4844(fork)) {
  // Blob transactions available
}

​

Hardfork Type

type BrandedHardfork = string & { __tag: "Hardfork" };

​

Core Operations

Hardfork.isAtLeast(current, target)  // current >= target
Hardfork.isBefore(current, target)    // current < target
Hardfork.compare(a, b)                // -1, 0, 1

Hardfork.hasEIP1559(fork)   // EIP-1559 base fee (London+)
Hardfork.hasEIP3855(fork)   // PUSH0 opcode (Shanghai+)
Hardfork.hasEIP4844(fork)   // Blob transactions (Cancun+)
Hardfork.isPostMerge(fork)  // Proof of Stake (Merge+)

Hardfork("cancun")        // Case-insensitive
Hardfork("paris")         // Alias → MERGE
Hardfork.toString(fork)              // Normalized name

​

API Methods

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Constructors

• fromString(value) - Parse hardfork name (case-insensitive, handles aliases)
• toString(fork) - Convert to normalized string name

​

Comparison Methods

• compare(a, b) - Three-way comparison (-1, 0, 1)
• isAtLeast(current, target) - Check if current >= target
• isBefore(current, target) - Check if current < target
• isAfter(current, target) - Check if current > target
• equals(a, b) - Equality check
• gte(a, b) - Greater than or equal (alias)
• lte(a, b) - Less than or equal (alias)
• gt(a, b) - Greater than (alias)
• lt(a, b) - Less than (alias)

​

Feature Detection

• hasEIP1559(fork) - EIP-1559 base fee mechanism (London+)
• hasEIP3855(fork) - PUSH0 opcode (Shanghai+)
• hasEIP4844(fork) - Blob transactions (Cancun+)
• hasEIP1153(fork) - Transient storage TLOAD/TSTORE (Cancun+)
• isPostMerge(fork) - Proof of Stake consensus (Merge+)

​

Collection Operations

• allNames() - Get all hardfork names (chronological order)
• allIds() - Get all hardfork IDs (chronological order)
• range(start, end) - Get hardforks between two versions (inclusive)
• min(forks) - Find earliest hardfork in array
• max(forks) - Find latest hardfork in array

​

Constants

FRONTIER, HOMESTEAD, DAO, TANGERINE_WHISTLE, SPURIOUS_DRAGON
BYZANTIUM, CONSTANTINOPLE, PETERSBURG, ISTANBUL, MUIR_GLACIER
BERLIN, LONDON, ARROW_GLACIER, GRAY_GLACIER, MERGE
SHANGHAI, CANCUN, PRAGUE, OSAKA

Hardfork.DEFAULT  // PRAGUE

​

Quick Examples

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Version Gating

import { Hardfork, CANCUN, LONDON } from 'tevm';

const fork = Hardfork("cancun");

// Check minimum version
if (Hardfork.isAtLeast(fork, LONDON)) {
  // EIP-1559 available
}

// Feature-based check
if (Hardfork.hasEIP4844(fork)) {
  // Use blob transactions
}

​

Network Configuration

import { InvalidFormatError } from 'tevm/errors'

function getNetworkCapabilities(hardfork: string) {
  const fork = Hardfork(hardfork);
  if (!fork) {
    throw new InvalidFormatError("Invalid hardfork", {
      value: hardfork,
      expected: "Valid hardfork name (e.g., 'cancun', 'london')",
      code: "INVALID_HARDFORK"
    })
  }

  return {
    consensus: Hardfork.isPostMerge(fork) ? "PoS" : "PoW",
    eip1559: Hardfork.hasEIP1559(fork),
    push0: Hardfork.hasEIP3855(fork),
    blobs: Hardfork.hasEIP4844(fork),
    transientStorage: Hardfork.hasEIP1153(fork),
  };
}

​

Upgrade Path

import { BERLIN, CANCUN, range } from 'tevm';

// Get all hardforks between two versions
const upgradePath = range(BERLIN, CANCUN);
// [BERLIN, LONDON, ARROW_GLACIER, GRAY_GLACIER, MERGE, SHANGHAI, CANCUN]

console.log(`${upgradePath.length} hardforks to upgrade through`);

​

Additional Documentation

• fundamentals.mdx - Introduction to Ethereum protocol upgrades
• hardforks.mdx - Complete hardfork timeline with all features
• usage-patterns.mdx - Common patterns and examples
• branded-hardfork.mdx - Branded type pattern
• wasm.mdx - WASM implementation status

​

Tree-Shaking

// Import specific features
import { hasEIP4844, isAtLeast, fromString } from 'tevm/Hardfork'

// Or import constants only
import { CANCUN, LONDON, BERLIN } from 'tevm/Hardfork'

// Selective imports reduce bundle size
const fork = fromString(userInput)
if (hasEIP4844(fork)) {
  // Blob logic
}

​

Performance

• Comparisons: Simple array index lookups (~10-20ns)
• Feature detection: Single comparison + branch (~15-30ns)
• String parsing: Hash table lookup (~50-100ns)
• String conversion: Array index (~20-40ns)

​

Implementation

• Type: Branded string (string & { __tag: "Hardfork" })
• Storage: Chronologically ordered array
• Comparison: Array index comparison
• Parsing: Hash table with lowercase keys
• Aliases: “paris” → MERGE, “constantinoplefix” → PETERSBURG

​

Best Practices

1. Use feature detection over version checks
   // Good - explicit about requirements
   if (Hardfork.hasEIP4844(fork)) { /* ... */ }
   
   // Less clear - couples to version
   if (Hardfork.isAtLeast(fork, CANCUN)) { /* ... */ }
   
2. Validate user input
   import { InvalidFormatError } from 'tevm/errors'
   
   const fork = Hardfork(userInput);
   if (!fork) {
     throw new InvalidFormatError("Invalid hardfork", {
       value: userInput,
       expected: "Valid hardfork name",
       code: "INVALID_HARDFORK"
     })
   }
   
3. Normalize for storage
   const normalized = Hardfork.toString(fork);
   
4. Use convenience forms for readability
   if (fork.supportsBlobs()) { /* ... */ }
   

​

Related Primitives

• Hardfork (Effect) - Effect.ts integration with Schema validation
• Network - Chain ID and network configuration
• Transaction - Transaction type selection based on hardfork
• Block - Block structure changes per hardfork