Fusaka-enabled Parent Upgrade Notice
This upgrade notice explains what you need to do if you operate a chain or a node running on a Fusaka-enabled Parent.
Note
For ArbOS 50 release information, please visit our Arbos release notes
Date of required actions
Dec 3rd 2025 for L2 chains that post L2 assertions Ethereum Mainnet
- L1 Mainnet upgrades to Fusaka:
Dec 3rd 2025- Applicable to Arbitrum (Orbit) chains and Arbitrum One/Nova operators
- L1 Sepolia upgrades to Fusaka:
October 14th 2025- Applicable to Arbitrum (Orbit) chains and Arbitrum One/Nova operators
- Arb One/Nova upgrades to ArbOS 50
- Learn more about the ArbOS 50 release
Required Node/Client Configurations for Orbit chains and ArbOne/Nova operators on Fusaka enabled parent chain
| Layer | Data Availability | Fallback to blobs enabled | Nitro version | Consenus Layer Client |
|---|---|---|---|---|
| L2 | Rollup | N/A | 3.8.0 or 3.7.6 | See table below |
| L2 | AnyTrust / AltDA | Yes > Fallback to blobs | 3.8.0 or 3.7.6 | See table below |
| L2 | AnyTrust / AltDA | No > Fallback to Calldata or disabled | No action required | No action required |
| L3 | Rollup | No action needed | No action required | No action required |
| L3 | AnyTrust / AltDA | No action needed | No action required | No action required |
Required configuration if you post blobs to a Fusaka-enabled parent chain
Consensus Client / Nitro Flags for operators (orbit or one/nova) chains that
| Client | Compatible with Nitro | Required Nitro Flag | Required Beacon Node Flag |
|---|---|---|---|
| Prysm | ✅ | None | --subscribe-all-data-subnets |
| Lighthouse | ✅ | None | --supernode |
| Teku | ✅ | --parent-chain.blob-client.dangerous.skip-blob-proof-verification | --p2p-subscribe-all-custody-subnets-enabled |
| Lodestar | ✅ | None | --supernode |
| Erigon Caplin | ❌ |
To read more about PeerDAS changes and why Layer 2 network operators must connect to an Ethereum beacon chain node with historical blob data, see the historical blobs docs.