Regolith

Table of Contents

• Overview

Overview

The Regolith upgrade, named after a material best described as "deposited dust on top of a layer of bedrock", implements minor changes to deposit processing, based on reports of the Sherlock Audit-contest and findings in the Bedrock Optimism Goerli testnet.

Summary of changes:

• The isSystemTx boolean is disabled, system transactions now use the same gas accounting rules as regular deposits.
• The actual deposit gas-usage is recorded in the receipt of the deposit transaction, and subtracted from the L2 block gas-pool. Unused gas of deposits is not refunded with ETH however, as it is burned on L1.
• The nonce value of the deposit sender account, before the transaction state-transition, is recorded in a new optional field (depositNonce), extending the transaction receipt (i.e. not present in pre-Regolith receipts).
• The recorded deposit nonce is used to correct the transaction and receipt metadata in RPC responses, including the contractAddress field of deposits that deploy contracts.
• The gas and depositNonce data is committed to as part of the consensus-representation of the receipt, enabling the data to be safely synced between independent L2 nodes.
• The L1-cost function was corrected to more closely match pre-Bedrock behavior.

The deposit specification specifies the deposit changes of the Regolith upgrade in more detail. The execution engine specification specifies the L1 cost function difference.

The Regolith upgrade uses a L2 block-timestamp activation-rule, and is specified in both the rollup-node (regolith_time) and execution engine (config.regolithTime).