Cardano's Van Rossem upgrade — Protocol Version 11 — reached its mainnet enactment target of May 21, 2026, making it the first hard fork in the blockchain's history to be ratified and activated through the on-chain Chang governance system rather than decided unilaterally by Input Output Global.
The enactment today follows a two-step governance sequence. A Plutus cost model parameter update was submitted to the PreProd testnet and ratified by Delegated Representatives and the Constitutional Committee on May 16. That vote cleared the path for the mainnet enactment now underway. The full hard fork governance action on PreProd is on-chain and targeting a separate ratification vote for May 29, per Intersect's Hard Fork Working Group.
What Protocol V11 changes
The upgrade is an intra-era hard fork, meaning it does not shift Cardano into a new era but adjusts protocol parameters within the Conway era. The core change is a Plutus cost model update — recalibrating the computational cost tables that govern how smart contract execution is priced on-chain. Node v11.0.1, released as mainnet-ready ahead of today's date, is now mandatory: node operators still running v10.7.1 cannot progress beyond the Protocol Version 11.0 hard fork boundary and must upgrade to continue operating, according to Intersect's weekly update published May 8.
The upgrade also advances governance mechanism tooling. DB-Sync 13.7.0.5, promoted to a full mainnet-ready release alongside node v11.0.1, is required for indexing services and explorers to remain compatible after the fork.
Why this fork is different
Every previous Cardano hard fork was initiated by IOG. Van Rossem is the first where DReps and the Constitutional Committee voted on-chain to approve the upgrade under the Chang governance architecture introduced by the Plomin hard fork. The governance action for the Plutus cost model was submitted, deliberated, and ratified through that process, with the resulting enactment date a product of community votes rather than an engineering release schedule set by the founding entity.
Intersect's Hard Fork Working Group has coordinated the activation sequence and published daily readiness tracking at cardanoupgrades.docs.intersectmbo.org throughout the approach.
Who Van Rossem was
The Hard Fork Working Group proposed naming the upgrade after Max van Rossem, a Dutch DRep who died before the fork bearing his name was initiated. Van Rossem ran the AmsterdamNode stake pool, organised four consecutive Cardano Summits in the Netherlands from 2021 through 2024, helped Amsterdam's first bar accept ADA, and served as co-lead of the Constitutional Committee Election Working Group that helped form Cardano's first elected Constitutional Committee. The Intersect tribute describes him as someone who "believed in planting digital trees in whose shade he would never sit." The community naming vote ran between January 13 and February 14, 2026.
What comes next
The harder governance test is the May 29 PreProd hard fork governance action vote, which must clear DRep and CC thresholds before mainnet hard fork enactment can follow. Midnight, Cardano's programmable privacy sidechain, launched on mainnet on March 30, 2026. Ouroboros Leios — the throughput-scaling overhaul — is entering testnet and is the next major protocol milestone on the 2026 roadmap.
ADA rose roughly 3% in the days ahead of the May 21 date, according to market data cited in community channels, though price has not moved sharply on the enactment itself — a pattern consistent with governance milestones that are well-telegraphed rather than surprise catalysts.