Solana Begins Testing Alpenglow Upgrade Targeting 150-Millisecond Finality

Solana’s Alpenglow consensus upgrade entered public-testnet testing on Sept. 23, according to CoinDesk. The rollout lets developers assess the consensus changes under network conditions before broader deployment.

Alpenglow is proposed to cut transaction finality from about 12.8 seconds to roughly 150 milliseconds, a design target also cited by the Solana Foundation. The testnet move is not a confirmed activation on Solana’s main network.

Alpenglow enters Solana public testnet

Alpenglow’s move into public-testnet testing is the latest disclosed milestone for the proposed upgrade. It has a 150-millisecond finality target, compared with approximately 12.8 seconds for the current system, which would substantially shorten the time to finality. The testnet move does not establish that the target has been achieved on Solana mainnet or set a final mainnet activation date.

Agave v4.3 is required, while Firedancer remains unsupported

Validator software compatibility is an immediate constraint for the test. Anza’s feature-gate tracker, updated Sept. 22, lists Alpenglow under SIMD-0326 as a testnet feature requiring Agave v4.3.0.

The tracker also says Firedancer and Frankendancer are not yet supported for the activation. Participation is therefore presently tied to the specified Agave client version rather than extending across those alternative validator-client implementations.

September 28 is tentative feature activation, not a confirmed mainnet launch

Anza’s v4.3 release schedule recorded a general-adoption recommendation for Agave v4.3 on Solana mainnet. It listed feature activation as tentative for Sept. 28, but did not describe that date as a confirmed Alpenglow mainnet launch.

The schedule leaves a separation between software-release planning, feature activation and the full deployment of the consensus upgrade. In its Sept. 14 update, the Solana Foundation said Alpenglow remained on track for a mainnet release later in 2026. Anza’s release tracker is more specific on the tentative Sept. 28 feature-activation entry, but does not provide a confirmed mainnet launch date for Alpenglow.

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