Base Activates Cobalt Hard Fork with Enhanced B20 Token Standard
Base, Coinbase's Ethereum Layer-2 network, is set to activate its Cobalt hard fork on mainnet on September 30. This upgrade comes after a successful test run on Base's Sepolia testnet on September 23. The Cobalt hard fork expands the B20 token standard with new features such as scheduled multipliers, transfer-blocking, and Union/Intersect policies.
The update also introduces validity transactions that enable conditional swaps, withdrawals, and other state-dependent actions. This means that users can now perform actions on the network only when certain conditions are met, such as a user's balance or storage requirements.
Cobalt also includes dynamic upgrades through an Ethereum smart contract that stores upgrade timestamps for Base nodes. This allows for live updates to be applied smoothly without disrupting the network. Additionally, the prover registration flow has been changed, making it faster and more secure using AWS Nitro attestations and P-384 hints.
This is the third protocol update in 2026 for Base, following Azul and Beryl upgrades. The next upgrade, Denim, is targeting October with native 200-millisecond blocks that replace Flashblocks with canonical block and RPC streams.