Solana starts testing upgrade that could cut finality from 12.8 seconds to 150 milliseconds
Alpenglow would let exchanges, bridges and merchants treat payments as irreversible almost immediately.
A planned upgrade to make Solana even faster has moved to a testnet, where developers will try to cut the time a payment takes to become irreversible from about 13 seconds to 0.15 seconds.
That moment is known as finality. Exchanges wait for it before crediting deposits, bridges wait before releasing money on another blockchain and merchants need it to know that a payment cannot be taken back.
The upgrade, called Alpenglow, is now being introduced on Solana’s public test network, a copy of the blockchain that uses tokens with no monetary value. Developers can test the migration, find problems and restart the network without putting users’ money at risk.
Solana currently uses a system called TowerBFT to reach consensus, the process through which validators agree on which transactions belong in the permanent record. Validators record their votes on the blockchain and stack enough of them across 32 slots before a block becomes final.
Alpenglow replaces that system with a voting protocol called Votor. Validators send votes directly to one another and can settle on a block after one or two rounds, removing the long chain of onchain votes.
Applications keep executing transactions as they do today, and users will not need to change wallets or how they send funds.
Alpenglow has spent more than four months running on a smaller network created specifically for the upgrade. Moving it to Solana’s established testnet checks whether the broader group of computers and services already running the blockchain can switch together.
Validators taking part need Agave 4.3. Agave is the main software used to run Solana and is maintained by Anza, one of the companies responsible for developing the network.
Anza recommended Agave 4.3 to all mainnet validators on Sept. 21 after first rolling it out to operators responsible for 10% and then 25% of the SOL used to secure the network.
Those alternatives are intended to reduce Solana’s reliance on a single piece of software, so a fault in Agave does not affect every validator at once. Their absence from the test means the first Alpenglow migration will run entirely through Agave.
Sept. 28 appears in Anza’s schedule as the tentative date for turning on features included in Agave 4.3 on the main network. It is not a confirmed Alpenglow launch date, and Anza’s tracker still listed the testnet switch itself as pending early Wednesday.
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Asanat Analysis — Why it matters
Alpenglow represents a meaningful technical pivot for Solana's throughput-to-finality tradeoff. Current 12.8-second finality already outpaces Ethereum Layer 1 (~13 minutes), but sub-200ms settlement would eliminate the practical difference between on-chain and centralized systems for point-of-sale transactions. This matters because payment rails (Stripe, Square competitors) have historically avoided crypto due to rollback risk; near-instant finality removes that friction.
The upgrade signals Solana is doubling down on merchant adoption rather than competing solely on raw TPS. Exchanges and bridges benefit most immediately—today they batch settle to manage finality risk. However, the second-order effect is architectural: achieving 150ms finality without sacrificing decentralization or requiring new validator hardware would validate Solana's core design thesis against criticism that its speed comes at centralization cost. If successful, it narrows the technical argument for alternative L1s.
Historical context: Solana's network has suffered multiple outages tied to validator load; tighter finality could either exacerbate this (more frequent state commits) or solve it (clearer consensus guarantees). The testing phase matters more than the announcement—real-world performance under load will determine whether this becomes competitive moat or incremental marginal gain.