Cardano develops a two-phase Dijkstra upgrade plan: Leios in 2026 and Peras in 2027

Cardano aims to implement Dijkstra Phase 1 in the fourth quarter of 2026, introducing Linear Leios and new ledger capabilities. Dijkstra Phase 1 will increase throughput with complementary Endorser Blocks and certifications. Ouroboros Peras plans to accelerate settlement through equity pool voting in the second quarter of 2027. Both phases require testnet deployment and governance approval before the main network can be activated.

Cardano sets the Dijkstra Phase 1 target for the fourth quarter of 2026.

Cardano plans to carry out a two-phase Dijkstra upgrade, with the first phase aiming to complete code in the fourth quarter of 2026 and the second phase planned to be in the second quarter of 2027. This upgrade will introduce Ouroboros Linear Leios and subsequently activate Ouroboros Peras. Phase 1 will also bring nested transactions, guard scripts, account address improvements, and other ledger changes. Phase 2 will focus on achieving faster settlements through the voting layer of the equity pool. Both phases require testing and on-chain governance approval to be activated on the main network.

Cardano's first Dijkstra phase will establish a new era of ledgers under version 12 of the protocol. The upgrade will activate Ouroboros Linear Leios while preparing Peras. The code completion target is the fourth quarter of 2026, but this date does not represent the final mainnetwork activation time.

Linear Leios will improve throughput with complementary Endorser Blocks and existing Praos Ranking Blocks. These Endorser Blocks reference additional transactions that can be processed by the network after authentication. As a result, Cardano can increase transaction capacity without relying on larger blocks or faster time slots.

An interest-based committee will authenticate Endorser Blocks through aggregate signatures. Certification requires a quorum of 75% of active interests, and then endorsed transactions can enter the ledger. If there is no certified Endorser Block, Ranking Blocks will continue to process transactions through standard Praos methods.

Phase 1 will also introduce structural changes required by Peras. These include codec extensions and protocol parameters that cannot be added in the hard forks of the era. Therefore, the Dijkstra era provided the basis for the activation of Peras in the second phase.

Dijkstra adds new transaction and ledger capabilities

The first phase will introduce a number of changes beyond Linear Leios. Nested transactions allow transactions to contain sub-transactions with independent witness and execution contexts. This provides additional flexibility for on-chain applications and supports more expressive transaction structures.

Dijkstra will also introduce guard scripts that can observe the validity of transactions without having to be executed as part of the cost or casting. This change supports transaction guards and serves as a dependency on the Plutus V4 script context.

Account address improvements will establish ledger level definitions for account-based addresses. At the same time, the upgrade will remove the isValid field from transactions and introduce non-separated block body serialization. These changes support updated ledgers and transaction structures.

Cardano will also simplify pledge reward withdrawals and remove DRep delegation requirements. In addition, rewards based on pledge leverage will introduce a leverage parameter. However, its default setting will maintain the current reward behavior until governance selects another value.

Peras activation is planned for the second quarter of 2027

The second Dijkstra phase is targeted for the second quarter of 2027 and will activate Ouroboros Peras. Unlike Phase 1, this change will use the intra-era hard fork within Dijkstra. Therefore, a new ledger era is not needed to activate Peras.

Peras will add a voting coverage layer to the existing Ouroboros Praos chain selection mechanism. The Equity Pool Committee will vote on the nearest chain tip, allowing chain tips with sufficient support to reach settlements faster. The agreement will not change the way blocks are produced.

Both Dijkstra phases will follow the deployment of Preview and Pre-production test nets. Phase 1 includes operator testing, Endorser Block propagation checks, integration verification, and throughput benchmarking. Phase 2 will include tests focusing on voting and settlement delays.

Mainnet activation requires governance approval and involves DRep, equity pool operators and the Constitutional Council. The announced fourth quarter 2026 and second quarter 2027 goals remain estimates of code completion and readiness. The actual hard fork date will depend on testing, governance and network readiness.