Base's Cobalt Upgrade Ships Validity Transactions, B20 Compliance Tools

Base's Cobalt upgrade went live on mainnet Sept. 30 at 18:00 UTC, according to Base's own documentation and CryptoBriefing's report on the activation — two weeks after Base lead Jesse Pollak called Validity Transactions a new primitive coming to Base, quote-tweeting a post that pegged the feature's arrival at an estimated end of month. @base confirmed the mainnet activation the same day, calling Cobalt the network's third upgrade of 2026.

Validity Transactions: conditional execution, not a conditional order book

Cobalt's core addition is Validity Transactions: signed transactions Base only includes once onchain conditions are met, keyed on "storage, block-number, and Flashblock-index predicates," per Base's documentation. A fourth predicate, balance, was part of that list at launch; Base pulled it from Validity Transactions entirely in a documentation update merged Oct. 1, stripping every balance-predicate reference from the Cobalt overview, the Validity Transactions spec, and the base_sendRawTransactionValidity RPC docs. The commit that merged the removal states why, in its own message on PR 2053: "The balance predicate is being disabled; account-state predicates enable targeting individual users. Storage, block_number, and flashblock_index remain supported." Cointelegraph describes the mechanism in practice: a trader could submit a swap that only becomes eligible for inclusion once an asset reaches a specified price, with a block-number deadline after which the order expires. The transaction itself isn't a resting order sitting on an exchange book — it's signed and submitted like any other transaction, just one Base won't execute until its conditions clear.

B20 issuers get compliance and corporate-action tools

Cobalt also expands B20, the token standard Base introduced with its Beryl upgrade on June 25 — B20 fully activated on July 8, after Base pushed the rollout back following two network outages, one of which froze the sequencer for roughly two hours. Per Base's documentation, the update adds new "Union" and "Intersect" policies to B20; Cointelegraph reports B20 lets an issuer stack several compliance checks onto a single asset — identity verification, accredited-investor status, and sanctions-list screening among them. Issuers can also schedule "multiplier" updates, which Cointelegraph's reporting says Base uses to run corporate actions such as stock splits: adjusting the share count a wallet displays without minting or burning tokens.

A more consequential addition: Cobalt lets an issuer designate administrators who can move tokens out of a flagged holder's wallet without that holder's approval and attach a public memo to the transfer, Cointelegraph reports. Unchained reports this replaces burnBlocked, a blunter Beryl-era tool that could only burn a blocked holder's tokens outright — Cobalt's version moves the balance instead to a new address such as a recovery wallet, a mechanism Unchained reports Base's own developer documentation describes as "a transfer, not a burn." The capability is opt-in per token: nothing happens until an issuer names which holders can be seized and which administrators are allowed to act.

Cobalt also changes how Base's own infrastructure upgrades

Two changes in Cobalt affect Base's own operations rather than token mechanics. A smart contract now stores upgrade timestamps that Base nodes query to apply protocol changes automatically, instead of coordinated manual rollouts — currently running in "metrics-only mode" on mainnet while Base validates it, per Base's documentation. Cobalt also migrates TEE signer registration to onchain attestation verification: AWS Nitro attestations are now verified fully onchain, replacing what the documentation describes as the prior RISC Zero and Boundless proving flow. Node operators were required to update to Base v1.4.2 ahead of the Sept. 30 activation, per CryptoBriefing, and Binance paused Base network transfers during the upgrade window as a precaution.

Where B20 is already carrying tokenized stocks

Coinbase's tokenized stocks are issued on Base as B20 tokens, per Base's own listings page. Cointelegraph reports Coinbase launched the lineup on Base on Aug. 25, starting with Apple, Nvidia, Meta, and Alphabet; Base's listings page now carries 10 tickers — also including Amazon, Microsoft, Tesla, MicroStrategy, SanDisk, and SpaceX — describing the tokens as 1:1-backed by shares in regulated custody and issued under Regulation S to holders outside the U.S. Neither source says which of B20's compliance policies, if any, Coinbase has turned on for these tokens: the listings page states no identity-verification, accredited-investor, or sanctions-screening requirement for them, and Cointelegraph frames those checks as options an issuer could enable, never as ones Coinbase has. The listings page's FAQ explains how dividends and splits are handled for these assets: through an onchain multiplier rather than a change to a holder's token balance — the raw token count stays the same while the multiplier scales to reflect dividends, reinvested after applicable withholding and fees, and splits, so the share-equivalent value updates without breaking a DeFi position built on the token. The compliance build-out lands on top of a tokenized-assets push Base has been visibly accelerating, including Descout's coverage of the SEC's conditional exemption for onchain tokenized-stock trading and of Aave V4's Base Equities Hub, which already lets eligible users post seven Coinbase-issued tokenized stocks like these as collateral to borrow USDC.

What's still open

Base's own roadmap lists Denim as the next upgrade, replacing Flashblocks with native 200-millisecond blocks: Base Sepolia is targeting October 2026, while Base Mainnet — the network this piece covers — is targeting November 2026. Validity Transactions can key off a Flashblock-index predicate; neither Base's documentation nor the coverage of Cobalt's launch says whether a Flashblock-indexed Validity Transaction still resolves the same way once Flashblocks are retired — that becomes testable once Denim ships. Unchained's reporting lays out how the seize-and-transfer tool works, but no source identifies an issuer that has turned it on, or a case where it has actually been used — also testable, as future B20 issuers either adopt it or don't. And Base has not published a tokenized-stock volume or corporate-action figure since Cobalt activated: no source shows a split or dividend event having actually run through the multiplier yet, and what Cobalt added here is the ability to schedule multiplier updates, not the multiplier mechanism itself.