What Is Alpenglow in Solana?
Alpenglow is Solana’s next-generation consensus protocol designed to replace Tower BFT. It introduces a two-phase approach — Vouch (fast pre-confirmation) and Roast (threshold signature finality) — targeting sub-second finality.
How Alpenglow differs from Tower BFT
| Aspect | Tower BFT | Alpenglow |
|---|---|---|
| Finality time | ~12 seconds | Sub-second (target) |
| Mechanism | Exponential lockout voting | Vouch + Roast threshold signature |
| Fork choice | Stake-weighted lockout | Simplified vouch-based |
Phases
- Vouch: Validators send vouch messages for blocks they consider valid, similar to votes but lighter weight.
- Roast: Once 2/3+ of stake has vouched, validators produce a single threshold signature that marks the block as final.
Impact on developers
For most applications, Alpenglow is transparent — RPC methods, commitment levels, and transaction formats remain the same. The main benefit is that finalized commitment resolves much faster. See the developer guide for details.
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