Base Cobalt upgrade adds conditional transactions and B20 controls

Base activated its Cobalt upgrade on mainnet on September 30, adding transactions that wait for specified conditions and new controls for B20 tokens. The changes let users set conditions for transaction inclusion and give issuers more ways to apply transfer rules and manage balances, according to The Block’s report on the launch.

How does a validity transaction wait for the right conditions?

A user signs a transaction and submits it with conditions drawn from onchain state; Base checks those conditions before deciding whether the transaction can enter a block. Base’s Cobalt overview says the predicates can check contract storage, block numbers and Flashblock positions. If every condition matches, the transaction competes for inclusion under normal fee rules. If not, it waits; a block deadline can make it expire.

For example, a trader can set a swap to become eligible only if a pool reaches a specified price before a given block. That works like a timed instruction: the user submits it once, and the network checks whether its terms hold before including it. The Block reported that the submitted transaction remains private until it lands; the conditions themselves are not recorded onchain, according to Base’s documentation.

What new rules can B20 issuers combine?

Issuers can combine two to four existing allowlists or blocklists using AND or OR logic, so a transfer can depend on more than one policy. For instance, an issuer can require a recipient to pass a KYC check while also not appearing on a sanctions blocklist. Base says the combined rule reads the underlying lists when a transfer is checked, avoiding the need to keep a separate offchain copy synchronized.

Cobalt also lets issuers schedule a change to a B20 asset’s display multiplier for a future time. Base’s documentation describes this as useful for corporate actions such as stock splits: the displayed balance changes when the scheduled time arrives, while the underlying token balance and transfer functions remain unchanged.

When can an administrator reassign a holder’s B20 balance?

The new seizeWithMemo function lets an issuer-authorized administrator move a balance to another address in one operation and record a memo onchain. It is a transfer, not a burn, so the token’s total supply does not change. Base’s documentation says the function is opt-in for each token: the issuer must configure a policy identifying seizable holders and authorize administrators before it can be used.

The change to watch is whether B20 issuers adopt these policy and balance-management functions, alongside use of validity transactions for conditional actions. Cobalt is live on mainnet; the new rules give issuers and users different controls over eligibility, balance display and transaction timing.