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Overview

Each entry under chains: in dokrypt.yaml defines a local blockchain node. You can run multiple chains simultaneously for multi-chain development.

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Basic Configuration

chains:
  ethereum:
    engine: anvil
    chain_id: 31337

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Engines

Dokrypt supports three EVM node engines:
EngineDescriptionBest For
anvilFoundry’s AnvilDefault. Fastest, most features.
hardhatHardhat NetworkHardhat ecosystem compatibility
gethGo-EthereumClosest to production
chains:
  ethereum:
    engine: anvil     # or hardhat, geth

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Chain ID

chains:
  ethereum:
    chain_id: 31337   # Any integer
Common local chain IDs: 31337 (Hardhat/Anvil default), 1337 (Geth default).

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Block Time

Controls how frequently blocks are produced. 
chains:
  ethereum:
    block_time: "2s"  # Produce a block every 2 seconds
ValueBehavior
"0s" or omittedInstant mining (mine on every transaction)
"1s" - "12s"Timed block production
"12s"Simulates Ethereum mainnet

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Mining Modes

chains:
  ethereum:
    mining:
      mode: auto       # auto | interval | manual
      interval: "2s"   # Only for interval mode
ModeBehavior
autoMine a block on every transaction
intervalMine at fixed intervals
manualOnly mine when explicitly requested via dokrypt chain mine

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Accounts

chains:
  ethereum:
    accounts: 10                        # Number of test accounts
    account_balance: "10000"            # Balance in ETH
    # OR
    balance: "10000000000000000000000"  # Balance in wei

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EVM Configuration

chains:
  ethereum:
    gas_limit: 30000000       # Block gas limit
    base_fee: 1000000000      # Base fee in wei (1 gwei)
    hardfork: shanghai        # london | shanghai | cancun
    code_size_limit: 24576    # Max contract code size
    auto_impersonate: false   # Auto-impersonate all accounts

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Forking

Fork a live network on startup: 
chains:
  ethereum:
    fork:
      network: mainnet          # Network name
      block_number: 18500000    # Fork at specific block (0 = latest)
With a custom RPC URL: 
chains:
  ethereum:
    fork:
      rpc_url: "${ALCHEMY_URL}"
      block_number: 18500000
Supported network names: mainnet, ethereum, sepolia, goerli, polygon, arbitrum, optimism, base, bsc, avalanche.

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Genesis Accounts

Pre-fund specific addresses at genesis: 
chains:
  ethereum:
    genesis_accounts:
      - address: "0x1234567890abcdef1234567890abcdef12345678"
        balance: "1000000000000000000000"  # 1000 ETH in wei
      - address: "0xabcdef1234567890abcdef1234567890abcdef12"
        balance: "500000000000000000000"   # 500 ETH in wei

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Auto-Deploy

Deploy contracts automatically when the chain starts: 
chains:
  ethereum:
    deploy:
      - artifact: "contracts/MyToken.sol:MyToken"
        constructor_args: ["MyToken", "MTK", 1000000]
        label: "token"
      - artifact: "contracts/Registry.sol:Registry"
        label: "registry"

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Multi-Chain Setup

Run multiple chains for cross-chain development: 
chains:
  ethereum:
    engine: anvil
    chain_id: 31337
    block_time: "2s"
  polygon:
    engine: anvil
    chain_id: 137
    block_time: "2s"
  arbitrum:
    engine: anvil
    chain_id: 42161
    block_time: "1s"
Use --chain flag to target a specific chain: 
dokrypt chain info --chain polygon
dokrypt chain mine 10 --chain arbitrum
dokrypt fork mainnet --chain ethereum

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Default Ports

Each chain gets a unique RPC port (assigned dynamically). The first chain typically gets port 8545.
Chain (in order)Default RPC Port
First chain8545
Second chain8546
Third chain8547