A hard fork is one of the most visible and celebrated moments in Cardano development, but rarely is it the work of a single team or a single decision.
By the time a hard fork reaches Mainnet, there will have been months of intense testing, coordination, trials, errors, governance discussions, infrastructure upgrades, and debates.

The van Rossem upgrade has been no exception to the above. While much of the conversation surrounding it understandably focuses on the technical changes being introduced, following the journey to enactment provides a useful insight into Cardano's governance processes working in practice across developers, infrastructure providers, DReps, SPOs, founding entities, and our wider community.

With this in mind, it is an appropriate time to thank all of those that have been involved in the Hard Fork Working Group (HFWG) to get us to this point. Including contributors from Input Output, Cardano Foundation, Emurgo, Midnight and Ensurable Systems, among so many others. All coordinating under the Intersect Hard Fork Working Group, in collaboration with the Intersect Technical Steering Committee. A reminder that the role of an MBO works well for technical coordination and managing a stable upgrade.

The state of play

Progress towards the van Rossem hard fork on Cardano Mainnet has been continuing across the Preview and Preprod test networks throughout the months of May and June 2026. The process has primarily involved two governance actions; a Plutus Cost Model (PCM) parameter update action and a hard fork initiation action.

Why two governance actions?

The Plutus Cost Model parameter update brings two key changes that take effect at two different stages. First of all, it contains increases in the cost model of some existing primitives. These take effect immediately after enactment and so it is vital that DApps and developers are prepared and have adjusted their settings accordingly if needed. Secondly, the update is preferred before the hard fork as it provides the settings for new primitives enabled by the hard fork itself, allowing them to be utilized immediately after hard fork enactment.

What has happened so far?

Following the Plutus Cost Model parameter update on April 17, 2026 at 00:00 UTC and the release of cardano-node-11.0.1 and db-sybc-13.7.0.5 early in May, the Preview test network hard forked to protocol version 11 on May 8, 2026 at 00:00 UTC.

On the Preprod test network, the Plutus Cost Model parameter update was enacted on May 16, 2026 at 00:00 UTC with DApps and developers highly encouraged to test their setups against the recent increases in a small number of existing primitives before progression to Mainnet. Although the hard fork initiation action was submitted to Preprod on May 8, 2026, ratification was held back while a resolution regarding Ogmios and Kupo tooling hard fork compatibility could be found.

The decision was made for Intersect to host forks of Ogmios and Kupo that could be made hard fork compatible, allowing testing to continue on Preprod. This seemingly small operational detail was a reminder that successful upgrades often depend not only on protocol development, but the many tools, services and contributors that support the wider ecosystem. Hard fork ratification then proceeded on June 5, with enactment taking place on June 10, 2026 at 00:00 UTC.

The remaining road on mainnet

Following successful enactments across Preview and Preprod networks, the Plutus Cost Model parameter update action was submitted to Mainnet on May 26, 2026. DReps and CC members ratified the update on June 13, 2026 with 68.57% DRep approval and 5/7 Constitutional Committee member votes. Enactment is scheduled for June 18, 2026 at 21:45 UTC.

When Mainnet?

Following a special meeting of the Hard Fork Working Group on June 15, 2026, the decision was made to approve the submission of the Mainnet hard fork initiation governance action in Epoch 637, with the support of the Intersect Technical Steering Committee. A proposed date of June 16, 2026 was agreed.

On-chain governance

Until now, a large focus of communications has been infrastructure releases, integrations and testing. Following the hard fork initiation governance action is submitted to Mainnet, the focus will shift to the Constitutional Committee, DReps and SPOs, the stakeholders responsible for executing Cardano’s decentralized on-chain governance system.

While the hard fork initiation action has been approved for submission in Epoch 637, it is acknowledged that some readiness targets remain in progress and some outstanding edge cases are also being investigated but are not considered to critically compromise progress. Therefore it is essential that DReps, SPOs and CC members voting on this action do so with as much information as possible. A link to the current Cardano constitution and useful readiness trackers are included below:

• Cardano constitution
• General: van Rossem upgrade readiness page
• SPO readiness: PoolTool | Cexplorer | ADAtool
• Exchange readiness: CardanoScan | Cexplorer

For long-time community members, the van Rossem hard fork is representative of a significant moment in Cardano's journey as the decisions around it have increasingly been made through the governance structures established by the Constitution and on-chain governance framework. The technical work remains essential, but the decision to proceed ultimately rests with the community's governance bodies. This article hopes to bring the wider ecosystem up to speed ahead of such votes, without burdening the reader with too much technical detail.

The proposals themselves will cover much of that but the hope is that this will at least help lay the groundwork for understanding the context of what has happened and what lies ahead.

Dates for the diary

June 16 - Mainnet - van Rossem HFGA submission - hard fork initiation

June 18 - Mainnet - Plutus Cost Model enactment - parameter update

Potential hard fork ratification dates:
June 23, 28
July 3, 8, 13, 18

Potential hard fork enactment dates: 
June 28
July 3, 8, 13, 18, 23

July 18 - Mainnet - van Rossem HF GA expiration- hard fork initiation

Additional Resources

Plutus Cost Model proposal metadata on Preview GovTool
Hard fork proposal metadata on Preview GovTool
Plutus Cost Model proposal metadata on PreProd AdaStat
Hard fork proposal metadata on PreProd AdaStat
Plutus Cost Model proposal metadata on Mainnet GovTool
Hard fork proposal metadata on Mainnet GovTool