Anza's Alpenglow goes live on Solana, cutting finality to 150 milliseconds

Solana Solana (SOL) validators replaced the network’s original consensus protocol on Wednesday, cutting transaction finality to milliseconds in a live-network upgrade.

In a statement shared with The Block, Solana core engineering firm Anza said its Alpenglow consensus protocol reached mainnet-beta at slot 459,653,000 at approximately 14:00 UTC. The deployment retires TowerBFT, the consensus protocol Solana had operated since its March 2020 launch.

The protocol shift condenses Solana's previous two-step transaction confirmation process into a single step, bringing finality down from 12.8 seconds to about 150 milliseconds for exchanges crediting deposits and merchants processing payments, according to Anza.

"This is the largest, most ambitious blockchain upgrade since 'The Merge,' and Anza took it from a white paper to running on mainnet in under 18 months," Anza CEO Brennan Watt said.

Anza first published the Alpenglow design in May 2025. It said the upgrade underwent public testing, which included red teaming, penetration testing, repeated migration rehearsals, and a security competition before the mainnet deployment.

Notably, the team outlined several further changes, though none have a confirmed release date. Rotor would change how block data moves across the network, while geographically aware leader rotations are intended to reduce delays between block producers, Anza said.

A separate research design, Quantumglow, would replace Alpenglow’s elliptic-curve cryptography with hash-based signatures to address post-quantum security while preserving its finality speed, according to the statement.

Jump Crypto’s Firedancer team proposed removing Solana’s 60 million compute-unit block limit in September 2025, after the planned Alpenglow upgrade. Proposal SIMD-0370 would let block capacity scale with validator hardware, rather than remain capped at a fixed limit.