Cardano Ledger Adds Leios Endorser Block Rules

The Cardano ledger development team has merged rules for processing Ouroboros Leios endorser blocks. Pull request #6215, titled “Add EB and EBLEDGERS,” was merged into the cardano-ledger repository’s master branch on October 30.

The update is part of the work preparing Cardano’s ledger for Leios, a proposed protocol extension designed to increase transaction throughput. Leios remains under development and is not active on Cardano mainnet.

How the New Cardano Ledger Rules Work

The ledger checks whether blocks and transactions are valid and determines how they change the network’s recorded state. The newly merged rules apply to the planned Dijkstra era and address how the ledger processes an endorser block and its transactions.

The first rule, EB, checks whether the hash of the block being applied matches the latest endorser block announcement recorded in the ledger state. It also rejects the block if no announcement is present.

The second rule, EBLEDGERS, processes the block’s transactions. In its initial form, it follows the existing LEDGERS rule used for transaction processing. The merged pull request also includes tests for the new rules.

Leios Certificates and Stake Pool Voting

Leios introduces endorser blocks alongside the existing Praos chain. The design allows these blocks to reference additional transactions, with a stake pool committee voting before those transactions can be incorporated into the ledger.

Under the current CIP-0164 proposal, the committee consists of the largest pools by active stake and is selected for an epoch. Votes are weighted by stake and combined using BLS signatures. The proposal describes a certificate threshold of 75% of total active stake as a feasible parameter value.

The ledger team merged a separate LEIOSCERT rule on October 27 to validate certificates and their timing. On October 29, it also merged a certificate validation interface intended for the consensus layer. The related development task describes a way to check a certificate when the information needed for validation is available but the endorser block itself has not yet been received.

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From Ledger Changes to the Dijkstra Hard Fork

The new ledger rules were merged after the cardano-node 11.2.0 pre-release. That version includes Dijkstra development features and groundwork for Leios, while the Leios functionality remains disabled by default.

According to minutes from Intersect’s Hard Fork Working Group, node 11.3 is planned to include linear Leios. The group described it as the first candidate that could be promoted to version 12.0, which would be capable of crossing the hard fork, provided testing does not identify blocking issues.

Input Output’s published rollout plan includes the Dijkstra hard fork, BLS key registration by stake pool operators, mainnet load exercises and later capacity increases through protocol parameter updates. Its initial target is approximately three to five times the current Praos ceiling of 4.5 kilobytes of transactions per second. Later updates target around ten to fifteen times that ceiling, subject to testing and governance decisions.