Cardano Confirms Two-Phase Dijkstra Roadmap: Leios in 2026, Ouroboros Peras in 2027

Cardano developers are sticking to a two-stage plan for the long-awaited Dijkstra upgrade, with Linear Leios and Nested Transactions slated for the first phase and Ouroboros Peras reserved for a separate activation in 2027. Intersect’s Aug. 14 update says the project remains on scope and schedule, and is now shifting focus toward ecosystem readiness, testnet reporting and support for alternative node implementations. What’s planned (and when) - Phase 1: introduces the Dijkstra ledger era, Linear Leios and Nested Transactions, plus new transaction/block serialization, PlutusV4 adjustments and several protocol parameters. Intersect lists Q4 2026 as the code-completion target; Haskell node teams are aiming for mainnet delivery by the end of 2026. Phase 1 will also install codec extensions and parameters that Peras will need—without activating Peras itself. - Phase 2: activates Ouroboros Peras via an intra-era hard fork, currently targeted for Q2 2027. That phase will require its own Preview and Pre-production deployments and a separate governance vote. The roadmap explicitly notes these dates are estimates, not guarantees: extensive testing and on-chain governance can push activation later. What Linear Leios and Peras actually do - Linear Leios: the main scaling element in Phase 1. It adds “Endorser Blocks” that can reference and certify extra transactions via stake-based committees. The design aims to raise throughput while keeping Cardano’s existing consensus guarantees (rather than replacing Praos). - Ouroboros Peras: adds a voting layer enabling committees of stake pool operators to vote on recent chain tips, helping the network reach settlement faster than relying solely on Praos chain-depth rules. Peras depends on the ledger structures and parameters installed by Phase 1. Node diversity and Amaru Dijkstra is also intended to broaden Cardano’s node-client ecosystem. Intersect highlighted Amaru, an open-source Rust node implementation that is already relay-capable and can validate and sync with the chain tip. Amaru’s development tracker lists these milestones: - General block-producer release: Sept. 30, 2026 - Dijkstra-compatible block producer: Oct. 29, 2026 - Leios-compatible release: Nov. 26, 2026 Mainnet block production for Amaru is targeted for November 2026. Intersect emphasizes these are development milestones, not guarantees of mainnet activation dates. The project is inviting alternative node teams into its weekly Hard Fork Working Group and is preparing a Dijkstra readiness tracker for testnet and ecosystem preparedness. Governance and constitutional changes Dijkstra introduces protocol parameters that cannot be altered by governance unless they are explicitly listed within the Constitution’s guardrails. Input Output (IO) plans a narrow constitutional amendment to add the relevant parameters and permitted ranges—without changing governance roles, voting thresholds or constitutional principles. The target is to submit that governance action no later than Epoch 655, which begins Sept. 11, 2026. Intersect’s Constitutional Amendment Portal had received four initial community submissions by Aug. 14. Context and caveats Cardano’s van Rossem hard fork moved mainnet to Protocol Version 11 in July, setting technical groundwork for Dijkstra and Leios. Intersect’s update (Weekly Update #124) reiterates that near-term work centers on finishing Dijkstra code, establishing readiness criteria and progressing Phase 1 through Preview and Pre-production before any mainnet governance vote. The primary caveat remains timing: while teams are targeting Q4 2026 and Q2 2027 for Phase 1 and Peras respectively, testing, governance, and broader ecosystem readiness could extend those timelines. Bottom line: Cardano’s Dijkstra upgrade is on a clear two-phase path—Leios and ledger work first, Peras later—with node diversity, testnets and constitutional housekeeping all moving in parallel as the community prepares for the next major evolution of the protocol.