Base’s Cobalt Upgrade Adds a New Rule Affecting Token Balances

Optional seizure controls are introduced by Base’s Cobalt upgrade, allowing B20 issuers to reassign holder balances under separate permissions.

Scheduled for mainnet rollout on September 30 at 18:00 UTC, Base’s Cobalt upgrade will let B20 token issuers configure balance seizures independently of standard transfer restrictions. For any token activating this capability, holders could retain normal transfer freedom while remaining subject to administrative reassignment.

Asset and Stablecoin variants make up B20, which is Base’s native ERC-20-compatible token standard. Administrative control over roles and policies governing balance movements is already granted by it, and oversight regarding administrative powers over those balances will now be managed as well.

Designated roles specify who can wield a specific power, whereas policy settings dictate which accounts are impacted by an operation. Separate permission checks are required for modifying a token’s rules versus executing a balance operation.

Separate Seizure Permissions#

Called seizeWithMemo, the new administrative operation is designed to shift a specific amount from a holder to another address, ensuring the total supply is preserved while standard transfer policies and holder allowances are bypassed.

Exemption statuses protecting accounts from balance loss must be configured by issuers before tokens can be taken via the function. When left unset, the SEIZE_EXEMPT_POLICY setting grants a blanket exemption to everyone. Setting up eligibility alone is not enough, as execution requires the SEIZE_ROLE, an active seizure function, an authorized recipient, and adequate funds.

Destination routes for confiscated tokens are dictated by a separate recipient policy, and leaving that rule unassigned permits any standard valid destination. Neither seizure-policy question is answered by a holder’s capacity to execute a regular transfer.

Sender and receiver addresses, along with the executor handling transfers on behalf of another account, are evaluated by B20’s existing transfer policies, which can be modified by administrators. Although a spender is approved, transfer checks are not bypassed, yet those standard transfer permissions are maintained completely separate from Cobalt’s seizure rules.

Already featured in B20 is the burnBlocked function, which allows designated callers to destroy tokens held by any account blocked under the transfer sender policy. While deprecated by Cobalt, that function remains callable with its original behavior intact.

Different methods for stripping a holder’s balance are left available to issuers, where tokens are kept in circulation at a separate address via reassignment, while wiping out the seized supply demands a subsequent burn action. Separate administrative roles and pause controls are maintained by seizure and burning functions.

Listed on Base’s status page as scheduled, the mainnet upgrade is slated for maintenance between 18:00 and 20:00 UTC, while Sepolia’s live status since Sept. 23 and the mainnet delivery on Sept. 30 are detailed in the upgrade overview.

Cobalt mainnet support is introduced in the v1.4.2 release, which directs node operators to complete their upgrades by September 30 at 18:00 UTC.