Base's Cobalt upgrade, set for mainnet on September 30, will let B20 token issuers split seizure permissions from normal transfer rules. This brings new ways to control token balances and exemptions.
B20 tokens on Base are about to get a new feature. With the Cobalt upgrade going live on mainnet September 30 at 18:00 UTC, token issuers will be able to set up administrative seizure rules that work separately from normal transfer restrictions. This changes how administrators can move or take away token balances.
Seizure and transfer now work separately
Cobalt introduces the seizeWithMemo function, allowing authorized administrators to reassign B20 token balances with an on-chain memo, independent of standard transfer permissions.
Several steps are needed for a seizure to happen. The issuer must give someone the SEIZE_ROLE, make sure the seizure function is not paused, pick a recipient who is allowed, and check that the account being targeted is not exempt. The SEIZE_EXEMPT_POLICY setting decides which accounts are protected. By default, all accounts are exempt unless the issuer changes this. Just setting up eligibility does not turn on seizure-explicit permissions and an active status are both needed.
Issuer controls and policy layers
B20 tokens already let administrators set roles and policies for moving balances. Cobalt goes further, letting issuers manage seizure and burning powers on their own. Transfer policies check the sender, receiver, and sometimes the executor, but these checks are separate from the new seizure rules. The burnBlocked function, which destroys tokens held by accounts blocked by the sender policy, is now deprecated but can still be used. Issuers now have several tools: they can reassign balances with seizure, destroy tokens with a burn, or allow transfers. Each tool has its own permissions and pause controls.
Cobalt is Base's third major upgrade in 2026, expanding tokenized asset infrastructure with Conditional and Validity Transactions, as well as new policy mechanisms for B20 tokens. The update also introduces Composite Policies and Schedule Multiplier Updates, while deprecating the older burnBlocked approach.
Upgrade timeline and node requirements
The Cobalt upgrade is set for mainnet on September 30, with maintenance planned from 18:00 to 20:00 UTC. Sepolia testnet has already been running Cobalt since September 23. Node operators must upgrade to version 1.4.2 by the mainnet deadline to stay compatible. EgonCoin says this upgrade is part of a wider move toward more detailed token controls, as seen in other recent protocol changes reported earlier.
B20 tokens come in Asset and Stablecoin types, and both are affected by these new controls. Seizure is off by default. Issuers must set up both eligibility and permissions before any seizure can happen. The upgrade does not change the total token supply unless a burn is done after seizure.
Market and security implications
The Cobalt upgrade does not change token prices or liquidity directly. But it does bring new operational and governance risks for holders. Once an issuer enables administrative seizure, balances can be reassigned without the holder's consent, even if normal transfers are still allowed. This split between transfer and seizure permissions may help issuers with compliance or enforcement, but it also raises questions about user trust and how transparent token governance really is.
Base's mainnet upgrade is scheduled, and node operators must update by September 30 at 18:00 UTC. Sepolia testnet has been running Cobalt since September 23, giving issuers and developers a live place to test the new features before mainnet launch.
Administrative seizure in token contracts is not new. But letting issuers separate seizure from transfer permissions is a real change. This gives issuers more ways to enforce compliance or meet regulatory demands, but it also adds complexity that many users may not notice. For U.S. investors and token holders, it is more important than ever to understand what administrative powers are built into a token contract, especially as more protocols add these detailed controls. As token standards change, the push and pull between issuer authority and holder freedom will keep shaping how digital assets work.
