Hardhat Precompile Registry

The Hardhat Precompile Registry serves as a middleware layer within the Hardhat Network environment, emulating the behavior of Arbitrum's native precompiled contracts. This system intercepts calls to specific reserved addresses (0x0...64 through 0x0...6c) and executes local handlers, allowing developers to test Arbitrum-specific logic, such as cross-chain messaging and gas estimation, without connecting to a live node.

Registry Architecture

The registry operates by injecting an L2-specific context into the execution environment.

PrecompileContext: Every call receives an enhanced context containing the current block number, chain ID, L1 base fee estimates, and access to the L1 message queue.
Handler Resolution: The registry maps target addresses to specific PrecompileHandler instances.
L1 Message Queue: A specialized queue that captures messages sent via sendTxToL1, simulating the Arbitrum Inbox behavior for local testing.

ArbGasInfo (`0x000000000000000000000000000000000000006c`)

The ArbGasInfo precompile provides essential information regarding gas scheduling, pricing components, and accounting parameters on Arbitrum Nitro.

Configuration

The handler supports runtime configuration via a node_state/gas_config.json file. This allows for the simulation of various network conditions (e.g., congestion, high L1 fees).

Configuration Schema:

JSON

{
  "l1BaseFee": "20000000000",
  "gasPriceComponents": {
    "l2BaseFee": "100000000",
    "l1CalldataCost": "16",
    "l1StorageCost": "0",
    "congestionFee": "0"
  },
  "gasAccounting": {
    "speedLimitPerSecond": "120000000",
    "gasPoolMax": "32000000",
    "maxTxGasLimit": "32000000",
    "amortizedCostCapBips": "10000"
  }
}

Supported Functions

Function	Selector	Description
`getPricesInWei()`	`0x41b247a8`	Returns a 6-tuple of gas components including L1 byte price, L2 base fee, and congestion fees.
`getPricesInArbGas()`	`0x02199f34`	Returns gas prices denominated in internal ArbGas units (3-tuple).
`getCurrentTxL1GasFees()`	`0xc6f7de0e`	Estimates L1 gas fees for the transaction using a local compression heuristic.
`getL1BaseFeeEstimate()`	`0xf5d6ded7`	Returns the current estimated L1 base fee (in wei).
`getL2BaseFeeEstimate()`	`0xb246b565`	Returns the current L2 base fee (in wei).
`getL1GasPriceEstimate()`	`0x055f362f`	Returns the estimated L1 gas price (typically matches L1 base fee).
`getGasAccountingParams()`	`0x612af178`	Returns the Speed Limit, Gas Pool Max, and Max Tx Gas Limit.
`getMinimumGasPrice()`	`0xf918379a`	Returns the minimum gas price required for a transaction.
`getAmortizedCostCapBips()`	`0x7a7d6beb`	Returns the amortized cost cap in basis points.
`getL1BlobBaseFeeEstimate()`	`0x67037bec`	Returns the estimated L1 blob base fee (EIP-4844 support).

L1 Cost Estimation

The getCurrentTxL1GasFees method implements a compression heuristic to approximate Mainnet behavior:

Zero Bytes: Charged at 4 gas per byte.
Non-Zero Bytes: Charged at the configured l1CalldataCost (default 16 gas).
Compression Discount: The total is discounted by a factor of 0.9 to simulate Brotli compression savings.

ArbSys (`0x0000000000000000000000000000000000000064`)

The ArbSys precompile acts as the primary interface for interacting with the underlying Arbitrum chain, providing system information and L2-to-L1 messaging capabilities.

Supported Functions

Function	Selector	Description
`arbChainID()`	`0xd127f54a`	Returns the configured Arbitrum chain ID (defaults to 42161).
`arbBlockNumber()`	`0xa3b1b31d`	Returns the current L2 block number.
`arbOSVersion()`	`0x051038f2`	Returns the current ArbOS version.
`sendTxToL1(address, bytes)`	`0x6e8c1d6f`	Sends a message to the L1 chain. In Hardhat, this queues a message in the `L1MessageQueue`.
`mapL1SenderContractAddressToL2Alias(address)`	`0xa0c12269`	Calculates the aliased L2 address for a given L1 contract address.

L2-to-L1 Messaging

The sendTxToL1 function is a core component for cross-chain communication (e.g., withdrawals). In the Hardhat environment, calling this function does not produce a real L1 transaction but instead:

Parses the destination address and data payload.
Generates a mock L2-to-L1 message.
Pushes the message into the PrecompileContext.l1MessageQueue.
Logs the event to the console for debugging visibility.

Address Aliasing

The mapL1SenderContractAddressToL2Alias function implements the standard Arbitrum aliasing formula used when L1 contracts initiate calls to L2:

TEXT

L2_Alias = L1_Address + 0x1111000000000000000000000000000000001111

This ensures that L1 contract addresses do not collide with native L2 EOA addresses.

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