Migration Guide

How to migrate from Kleros V1 to V2

Migration Guide: V1 to V2

This guide covers the key differences between Kleros V1 and V2 and what changes are needed for jurors, developers, and users migrating to the new protocol.

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For Jurors

What Changed

Aspect	V1 (Ethereum)	V2 (Arbitrum)
Network	Ethereum Mainnet (+ xDAI)	Arbitrum One
PNK Staking	PNK stays in wallet	PNK transfers to KlerosCore contract
Gas Costs	High (Ethereum gas)	Low (Arbitrum gas)
Minimum Stake	Varies (e.g., 1,000 PNK for Onboarding)	Varies per court (check live court UI)
Vote Privacy	Basic commit-reveal	Commit-reveal (Shutter encryption in development)

Migration Steps

1. Bridge PNK to Arbitrum

   Use the Arbitrum Bridge or a cross-chain bridge to move PNK from Ethereum to Arbitrum One.

2. Bridge ETH for gas

   You need a small amount of ETH on Arbitrum for transaction fees. Bridge or send ETH to your Arbitrum address.

3. Stake in V2 Court

   Visit court.kleros.io, connect your wallet on Arbitrum, and stake PNK in your chosen court. You will need to approve PNK spending first.

In V2, staking PNK transfers tokens to the KlerosCore contract. This is different from V1 where PNK remained in your wallet. Your staked PNK is still yours and can be unstaked, but it is held by the contract while staked.

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For Developers

Key Architecture Changes

V2 significantly simplifies integration compared to V1:

Responsibility	V1	V2
Evidence handling	Arbitrable contract	Handled by Court
Appeal logic	Arbitrable contract	Handled by Court
Crowdfunding appeals	Complex arbitrable logic	Built into Court
Dispute creation	Direct call to arbitrator	Direct call to KlerosCore
Ruling reception	Same (rule() callback)	Same (rule() callback)

The core change for developers: evidence submission and appeal management are now handled entirely by the Court. Your arbitrable contract no longer needs to implement these.

Interface Changes

V1 used the ERC-792 arbitration standard. V2 uses an updated interface:

• IArbitrableV2 replaces IArbitrable
• DisputeTemplate replaces MetaEvidence for defining dispute context
• Evidence is submitted directly to the Court, not logged by the arbitrable
• extraData encoding includes court ID and number of jurors

For detailed integration guidance, see the Developers section.

Cross-Chain Support

V2 supports disputes from any EVM chain via the VEA bridge. If your application is on Ethereum Mainnet or another chain, disputes can be bridged to Arbitrum for resolution, with rulings bridged back. Applications natively on Arbitrum interact directly with KlerosCore without bridging.

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For Product Users

Most Kleros products now have V2 versions:

• Court: Use court.kleros.io (V2 on Arbitrum)
• Escrow: Use escrow.kleros.io (V2 on Arbitrum)
• Curate: Use curate.kleros.io (V2 on Arbitrum)

Products that still use V1 (Scout, Reality, PoH) will provide migration paths when their V2 versions are ready.

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Need Help?

For migration support, contact the Kleros team at [e-mail] or ask in the Discord.