Base activates Cobalt upgrade adding Validity Transactions and B20 seizure rules
Base activated Cobalt on mainnet on September 30, adding Validity Transactions and letting B20 issuers reassign holder balances to another wallet with an onchain note.
Why it matters
Token issuers on Base gain administrative control over holder balances that previously existed only as a burn, so custody, exchange and asset-management products built on B20 tokens have new rules to account for. Bitcoin Insider said developers building on the chain should account for the change. Validity Transactions apply to the network generally rather than to B20 alone, so the effect on non-B20 assets is limited.
Where the sources disagree
Whether a scheduled B20 adjustment touches the underlying balance
displayed share count changes, underlying balance unchanged
Cointelegraph
displayed token balances change at a future time
Crypto.News
Cointelegraph says a scheduled stock split changes the shares shown in wallets and apps without minting, burning or altering the underlying balance, while Crypto.News says a scheduled multiplier changes displayed token balances at a future time.
Whether the B20 seizure rules are already in force
seizure rules scheduled and not yet described as active
CryptoSlate
upgrade live on mainnet Wednesday
Cointelegraph, Unchained
CryptoSlate describes the seizure configuration as something issuers 'will' be able to set, while Cointelegraph and Unchained report the upgrade as activated on mainnet on Wednesday.
How much technical detail the reporting provides on the new rule
mechanism and affected token categories unspecified
Bitcoin Insider
seizeWithMemo on B20, which has Asset and Stablecoin variants
CryptoSlate
Bitcoin Insider says the reporting does not specify the technical mechanism behind the new rule or which categories of token are affected, while CryptoSlate names the mechanism as seizeWithMemo on B20, which exists in Asset and Stablecoin variants.
Key facts
Base activated Cobalt on mainnet at 18:00 UTC on September 30, with the status page marking the maintenance window complete at 20:00 UTC.
Reported by Cointelegraph
Cobalt is the third major upgrade Base has shipped, following Beryl, which introduced B20.
Reported by Cointelegraph
Validity Transactions let users submit a transaction that becomes eligible for inclusion only when preset onchain conditions are met, with a deadline after which it expires, and submissions can stay private until they are included.
Reported by Cointelegraph
The new B20 operation seizeWithMemo moves a holder's balance to another address with an onchain note instead of destroying it, preserves total supply and skips ordinary transfer policies and holder allowances.
Reported by Unchained
Base deprecated burnBlocked from the Beryl upgrade but left it callable, and the blocked-account burn still destroys tokens.
Reported by Unchained
Issuers can combine two to four existing allowlists or blocklists, including lists kept by a KYC provider, into one rule using AND or OR logic, which Crypto.News describes as two composite policy types named Union and Intersect.
Reported by Cointelegraph
A scheduled multiplier can change displayed token balances at a future time without each holder signing a transaction.
Disputed figureReported by Cointelegraph
Seizure stays disabled until an issuer configures which accounts are exempt and grants seize permission to specific administrators, and Base states it does not initiate or direct such a transfer.
Reported by Cointelegraph
What happened
Base activated Cobalt, its third major upgrade, on its Ethereum layer-2 mainnet at 18:00 UTC on September 30, with Cointelegraph, Unchained and Bitcoin.com News all describing it as live that Wednesday. The upgrade carries two main pieces: Validity Transactions, which let a user hold a signed transaction until a preset onchain condition is met and set an expiry after which it dies, and an expansion of the B20 token standard introduced with the earlier Beryl upgrade. Unchained, CryptoSlate and Crypto.News all identify the same issuer power as the headline change, a B20 operation called seizeWithMemo that moves a holder's balance to another address with a public note recorded onchain instead of destroying it; Base's developer documentation calls it 'A transfer, not a burn'. CryptoSlate adds that it preserves total supply and skips ordinary transfer policies and holder allowances. Issuers can now combine two to four existing allowlists or blocklists, including lists held by a KYC provider, into one AND or OR rule, which Crypto.News describes as two composite policy types named Union and Intersect. Seizure is opt-in per token: it does nothing until an issuer names eligible holders and grants the permission to specific administrators, and Base says issuers control whether it is enabled while Base itself does not initiate or direct the transfer. Two points are not fully reconciled: Cointelegraph says a scheduled stock split changes displayed shares without minting, burning or altering the underlying balance, while Crypto.News says a scheduled multiplier changes displayed token balances, and CryptoSlate still writes the seizure rules in the future tense although the other outlets report them as active.
How the story developed
- First report
First report by Cointelegraph
Base completes Cobalt upgrade, adds new tools for tokenized assets
- Update
First reports of Cobalt landing on Base mainnet
Cointelegraph and Unchained publish within seconds of each other on the activation, and both point to a Base announcement.
- Official statement
Base publishes the upgrade announcement and developer documentation
The blog post and developer docs describe Validity Transactions, B20 composite policies and the opt-in seizure permission.
- Independent corroboration
Independently corroborated by Unchained
Base’s Cobalt Upgrade Lets Token Issuers Move Seized Balances Instead of Burning Them
- Official statement
Base status page marks the mainnet maintenance window complete
The window was listed for 18:00 UTC and marked complete at 20:00 UTC.
- Official statement
Official statement from Bitcoin.com News
Coinbase-Backed Base Gives Users More Control With Cobalt Upgrade
- Update
CryptoSlate details separate seizure permissions and role-versus-policy checks
The report sets out that changing a token's rules and executing a balance operation are distinct permission checks, and that the blocked-account burn still destroys tokens.
- Update
Cobalt reaches Sepolia a week ahead of mainnet
The Cobalt upgrade specification records a Sepolia activation seven days before the mainnet one.
- Update
Crypto.News records the spec details outside B20
Mainnet node minimum was v1.4.2, a scheduled fee payment in B20 tokens was removed from this fork, and the fork adds a monitoring-mode registry for future upgrade scheduling plus an onchain method for registering certain trusted-execution-environment prover signers.
How coverage built up
Independent sources over time, counted the way the consensus panel counts them: a republication of a wire story does not move the line.
- 30 Sept 2026, 19:00 UTC: Cointelegraph — 1 independent source, 1 reports
- 30 Sept 2026, 19:00 UTC: Unchained — 2 independent sources, 2 reports
- 30 Sept 2026, 21:40 UTC: Bitcoin.com News, official — 3 independent sources, 3 reports
- 1 Oct 2026, 07:30 UTC: CryptoSlate — 4 independent sources, 4 reports
- 1 Oct 2026, 09:44 UTC: Crypto.News — 5 independent sources, 5 reports
- 1 Oct 2026, 09:45 UTC: Bitcoin Insider — 6 independent sources, 6 reports
Affected entities
Also mentioned: Optimism
Original sources
| Publisher | Report | Role | Published |
|---|---|---|---|
| Bitcoin.com News Company, official | Coinbase-Backed Base Gives Users More Control With Cobalt Upgrade | Independent | |
| Cointelegraph Crypto media | Base completes Cobalt upgrade, adds new tools for tokenized assets | Original | |
| Unchained Crypto media | Base’s Cobalt Upgrade Lets Token Issuers Move Seized Balances Instead of Burning Them | Independent | |
| CryptoSlate Crypto media | Base’s Cobalt upgrade adds another rule to affect token balances | Independent | |
| Crypto.News Crypto media | Base Cobalt upgrade puts new controls inside tokenized assets | Independent | |
| Bitcoin Insider Aggregator | New Rule in Base’s Cobalt Upgrade Will Affect Token Balances | Syndicated |
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