Solana has begun testing its Alpenglow upgrade on the public testnet, with developers targeting a reduction in transaction finality from roughly 13 seconds to 150 milliseconds.

The change could allow crypto exchanges, bridges and merchants to confirm transactions as irreversible almost immediately.

Finality is the point at which a transaction is considered permanent and cannot be reversed. Exchanges typically wait for that confirmation before crediting deposits, bridges depend on it before releasing assets on another chain, and merchants use it to verify that payments are final.

The Alpenglow test is taking place on Solana’s public testnet, a version of the network that uses tokens without monetary value. Developers can use the environment to test the migration, uncover potential failures and restart the network without risking real funds.

Solana currently relies on TowerBFT to coordinate validator consensus. Validators vote on transactions and record those votes onchain, with enough support accumulating across 32 slots before a block becomes final.

Alpenglow would introduce Votor in place of TowerBFT. The new protocol allows validators to exchange votes directly and potentially finalize blocks within one or two rounds, eliminating much of the existing onchain voting process.

The underlying user experience is expected to remain unchanged. Applications can continue submitting transactions normally, and users will not need to modify their wallets or change how they send assets.

Before reaching the public testnet, Alpenglow had been operating for more than four months on a smaller network built specifically for development and testing. The latest stage will determine whether Solana’s larger validator and infrastructure ecosystem can migrate to the new system together.

Validators participating in the test need to install Agave 4.3, the primary software implementation used by Solana validators. Anza, one of the companies working on Solana development, maintains Agave.

Anza recommended the software for mainnet validators on Sept. 21 after progressively deploying it to operators representing 10% and then 25% of the SOL securing the network.

Alternative validator implementations Firedancer and Frankendancer, both developed by Jump Crypto, have yet to support the Alpenglow test.

Those clients are designed to give Solana greater software diversity and reduce reliance on a single validator implementation. Their absence means the first Alpenglow migration will be tested exclusively through Agave.

Anza’s roadmap currently identifies Sept. 28 as a tentative date for activating the features bundled into Agave 4.3 on mainnet. It is not a confirmed date for the Alpenglow launch, and the company’s tracker continued to show the public testnet activation as pending as of early Wednesday.