Cardano will split its Dijkstra ledger upgrade into two hard forks: a Q4 2026 fork that activates Ouroboros Linear Leios, and a Q2 2027 fork that switches on Ouroboros Peras. The first phase builds the ledger changes both scaling mechanisms need, so the second can launch without a new ledger era.
Cardano will roll out its Dijkstra era upgrade in two stages, activating Ouroboros Linear Leios through a Q4 2026 hard fork and Ouroboros Peras through a Q2 2027 upgrade. Both changes fall under the same ledger overhaul, but each has its own rollout date.
Phase one sets up both scaling mechanisms
The first phase introduces Dijkstra as a new ledger era under Protocol Version 12, letting Cardano deploy the block structures, serialization changes and protocol parameters that Leios and Peras both need. As a result, Peras can then switch on through an intra-era hard fork because its codec extensions and parameters will already be in place.
Linear Leios adds parallel blocks
Linear Leios, the headline feature of phase one, aims to boost network throughput by letting block producers publish supplementary Endorser Blocks alongside existing Praos Ranking Blocks. These Endorser Blocks reference additional transactions, which a stake-based committee certifies before they enter the ledger. The upgrade is intended to increase transaction capacity without requiring larger regular blocks or faster block production.
Dijkstra will also include Nested Transactions, a new script type for transaction validity observation, along with Phase 1 account address improvements, PlutusV4 script context changes, updated transaction serialization, reference-script pricing and limits, and changes to staking reward withdrawals.
Rollout still needs governance approval
Both phases will follow the same path through Preview testnet, Pre-production testnet and mainnet, with governance actions required before each hard fork. Cardano said the Q4 2026 and Q2 2027 dates are estimated code-completion and mainnet-ready targets that do not include testing, governance or community approval timelines.
Source: Crypto Briefing
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