Solana is moving its Alpenglow consensus upgrade into public testnet testing as developers work on a major change that could make transactions reach finality much faster.
The upgrade is designed to reduce Solana’s transaction finality time from around 13 seconds to about 150 milliseconds. Finality is the point when a transaction is considered permanent and cannot normally be reversed under the network’s consensus rules.
This is especially important for exchanges, blockchain bridges, and other services that need to know when a transaction is safely confirmed before completing another action.
Alpenglow will replace Solana’s current TowerBFT consensus system with a new protocol called Votor. Instead of relying on a long series of onchain votes, validators will be able to communicate directly and reach agreement through one or two voting rounds.
Under the current system, validators build up enough votes across multiple slots before a block reaches finality. Alpenglow is designed to remove much of that waiting time while keeping the way users and applications send transactions mostly unchanged.
The move to public testnet comes after Alpenglow spent more than four months being tested on a smaller community network. The public testnet will give more validators, infrastructure providers, and developers a chance to test the upgrade under broader conditions.
Because the public testnet uses tokens with no real monetary value, developers can restart the network, test the upgrade, and fix problems without putting real funds at risk.
Anza, one of Solana’s main development teams, first began community validator testing in May. The team described Alpenglow as one of the biggest changes to Solana’s consensus system.
The new Votor system is designed to reach finality through one of two paths depending on how much validator participation is available. When enough stake participates, finality could be reached after one voting round. A second round provides another path when participation is lower.
Anza estimates that Alpenglow could bring median finality down to around 150 milliseconds. Earlier testing also showed that finality could potentially reach around 100 milliseconds under favorable conditions.
For regular Solana users, the biggest changes will happen behind the scenes. Wallets and applications will continue using the network in much the same way, while validators will use the new system to communicate and agree on the permanent state of the blockchain.
The Alpenglow test requires validators to run Agave 4.3, the latest version of Solana’s main validator software maintained by Anza.
Anza recommended Agave 4.3 for wider mainnet validator adoption on September 21. The software rollout has been gradual, with selected validators upgrading first before the recommendation was expanded.
A September 28 date appears in Anza’s Agave 4.3 schedule for a possible resumption of mainnet feature activation. However, that date should not be treated as a confirmed launch date for Alpenglow.
Alpenglow still has to complete its testing and activation process before it can be considered for Solana’s main network.
The upgrade is also separate from Solana’s recent work to reduce slot times.
Solana recently reduced its target slot time from 300 milliseconds to 250 milliseconds through SIMD-0525. The network is eventually targeting 200-millisecond slots, although no confirmed mainnet activation date has been set for that final stage.
Slot time and transaction finality are not the same thing. Slot time measures how quickly new slots are produced, while Alpenglow changes how quickly validators can agree that a block is final.
Another important point is that Firedancer and Frankendancer, validator clients developed by Jump Crypto, do not currently support the Alpenglow test.
That means the first public testing phase will rely on Agave validators. Solana has been working toward greater client diversity, since having multiple independent validator implementations can reduce the risk that a software problem affects the entire network.
Firedancer has already begun producing blocks on Solana’s mainnet after years of development. Frankendancer is a hybrid implementation that combines parts of Firedancer with existing Solana software.
For now, however, neither client is listed as supporting the Alpenglow upgrade.
The next stage will give developers and validators a much broader environment to test the new consensus system. If testing goes well and the required network upgrades and validator support are completed, Alpenglow could eventually bring a major reduction in the time Solana needs to finalize transactions.
