Base activates Cobalt: conditional transactions and B20 seize-with-memo go live

Base activated Cobalt, its third mainnet upgrade after Beryl, on September 30, 2026, according to a Base team announcement picked up by The Block and confirmed by Cryptobriefing and Cointelegraph. The upgrade shipped after activation on the Sepolia testnet earlier this month.

What Cobalt ships

Two feature sets landed in one hardfork:

• Validity Transactions. Time-bound orders that stay dormant until the sequencer sees the on-chain condition the sender specified. Example given by the Base team: a swap that only becomes eligible for inclusion when a pool price reaches a target USDC value before a given block. If the condition is not met before the deadline, the transaction is never included. Submissions stay private in the API until they land.
• B20 token-standard enhancements. B20 is the compliance-oriented token standard Base shipped with Beryl in June for issuers of regulated assets. Cobalt adds three functions:
  • Composite Policies — allowlists and blocklists can now be combined with OR/AND logic, so issuers can enforce KYC and sanctions screening in a single rule.
  • Schedule Multiplier Updates — aligns B20 with the draft ERC-8056 standard, letting issuers schedule balance-display changes such as stock splits or reverse splits without redeploying the token.
  • seizeWithMemo — authorized administrators can reassign balances (court order, sanctions freeze) while writing a memo on-chain, rather than burning tokens to a sink address. Unchained notes this replaces the burn-and-reissue pattern issuers previously used.

Context

Cobalt is Base's third named upgrade in 2026. The June Beryl hardfork added the B20 precompile, cut the L1 withdrawal delay from 7 to 5 days, and landed Reth V2. Beryl also produced the two-hour Base sequencer stall at block 47,806,542 on the day it activated.

Base's team says the next milestones after Cobalt are block times from 2 seconds down to 200ms, native smart accounts with gas sponsorship, and pulling in EVM changes from Ethereum's upcoming Glamsterdam upgrade. None of those are in this hardfork.

What to watch

1. Validity Transaction adoption on Base DEXs. Uniswap, Aerodrome and BaseSwap are the obvious first integrations; the feature's utility depends on the aggregators wiring conditional orders into their routers.
2. B20 issuer uptake. The seizeWithMemo function is regulator-shaped: watch whether US-regulated tokenized-security issuers (Ondo, Backed, Franklin Templeton's BENJI already lives on Base) migrate away from burn-based seizure to the new function.
3. ERC-8056 finalization. Cobalt's schedule-multiplier feature ships against a draft ERC. If the standard changes materially before finalization, Base will need to ship a compatibility path.

Base's docs at docs.base.org/upgrades/overview list the full Cobalt changelog and the sequence of prior hardforks. The Base team's release notes are the primary source; Coinbase leadership has not published a separate comment on Cobalt at the time of writing.