Pectra Blob Schedule Derivation

Table of Contents

• If enabled
• If disabled (default)
• Motivation and Rationale

If enabled

If this hardfork is enabled (i.e. if there is a non nil hardfork activation timestamp set), the following rules apply:

When setting the L1 Attributes Deposited Transaction, the adoption of the Pectra blob base fee update fraction (see EIP-7691) occurs for L2 blocks with an L1 origin equal to or greater than the hard fork timestamp. For L2 blocks with an L1 origin less than the hard fork timestamp, the Cancun blob base fee update fraction is used (see EIP-4844).

If disabled (default)

If the hardfork activation timestamp is nil, the blob base fee update rules which are active at any given L1 block will apply to the L1 Attributes Deposited Transaction.

Motivation and Rationale

Due to a consensus layer bug, OPStack chains on Holesky and Sepolia running oficially released op-node software did not update their blob base fee update fraction (for L1 Attributes Deposited Transaction) in tandem with the Prague upgrade on L1.

These chains, or any OPStack chain with a sequencer running the buggy consensus code¹ when Holesky/Sepolia activated Pectra, will have an inaccurate blob base fee in the L1Block contract. This optional fork is a mechanism to bring those chains back in line. It is unnecessary for chains using Ethereum mainnet for L1 and running op-node v1.12.0 or later before Pectra activates on L1.

Activating by L1 origin preserves the invariant that the L1BlockInfo is constant for blocks with the same epoch.