Solana Moves Alpenglow Upgrade to Public Testnet for 150ms Finality

Solana has moved its Alpenglow consensus upgrade to a public testnet, testing a new system designed to reduce transaction finality from roughly 13 seconds to about 150 milliseconds.

Finality is the point at which a blockchain transaction is treated as irreversible. Exchanges generally wait for that point before crediting deposits, while cross-chain bridges use it before releasing funds.

Alpenglow is designed to replace TowerBFT with Votor, a voting protocol that lets validators exchange votes directly and reach agreement in one or two rounds. TowerBFT records validator votes on-chain and requires 32 slots, or about 13 seconds, before a block becomes final.

The public testnet follows more than four months of operation on a smaller dedicated network. It uses test tokens with no real value, allowing developers to test, debug and reset the network without affecting user funds.

Validators participating in the migration must run Agave 4.3, Solana’s main validator software maintained by Anza. Firedancer and Frankendancer, alternative validator clients developed by Jump Crypto, do not yet support the Alpenglow test.

As a result, the initial testing phase depends on a single validator client. Operators representing 10% and 25% of total Solana (SOL) stake are scheduled to upgrade in stages before broader deployment.

The upgrade does not change Solana’s virtual machine, transaction formats, programs, fees or account model. Validators, indexers and other infrastructure connected to consensus may need updates.

The public testnet expands on Solana’s earlier Alpenglow activation plan, which outlined the same finality target while preserving the network’s existing application environment.

Alpenglow’s mainnet activation is tentatively scheduled for Sept. 28.