Solana switches to Alpenglow consensus tonight; Upbit halts SOL deposits and withdrawals

Solana (SOL) will replace TowerBFT, the consensus mechanism it has run since launch, with a new design called Alpenglow on the night of Oct. 21, Korea time. Anza, Solana's core developer, said on X on Oct. 13 that "Alpenglow goes live on mainnet-beta Wednesday, October 21," calling it "18 months of work for a migration that happens in one slot." In South Korea, crypto exchange Upbit will suspend deposits and withdrawals of SOL and 38 other Solana-based assets, 39 in all, from 6 p.m. KST on Oct. 21 to accommodate the upgrade.

Deposits and withdrawals of 39 assets, including SOL and USDC, stop at 6 p.m.

In a notice posted Oct. 20, Upbit said it will halt deposits and withdrawals from 6 p.m. KST on Oct. 21 until the network is confirmed stable, citing the Solana network upgrade. The 39 affected assets include Solana (SOL), USD Coin (USDC), Official Trump (TRUMP), Jupiter (JUP), Pudgy Penguins (PENGU), Render (RENDER) and Pyth Network (PYTH). Withdrawals of Bonk (BONK) and Drift (DRIFT), which were already delisted and open for withdrawal only, will also stop. Trading continues without interruption.

Votes move off-chain, cutting finality to 0.15 seconds

Under TowerBFT, validators submit on-chain vote transactions for each block, and it takes about 12.8 seconds from block creation to finality. Votor, Alpenglow's voting module, keeps votes off the chain and has validators exchange them directly as signed messages. A block is finalized in one round of voting if 80% of stake responds, or in two rounds if 60% responds. Anza expects finality of about 150 milliseconds (0.15 seconds) at the median, and as fast as 100 milliseconds. Those figures come from simulations based on the current mainnet stake distribution and exclude computation overhead.

The 150 milliseconds is the time to finality, not the block interval. Separately, the block interval, or slot time, was cut from 400 milliseconds to 200 milliseconds in four stages completed in October. According to Solana's official guide, the execution environment (SVM), transaction formats and fees do not change, and wallets and apps work as they do today. Because vote transactions leave blocks, however, on-chain transaction counts and transactions-per-second (TPS) figures will appear lower even though actual activity has not dropped. Rotor, the second module that will handle data dissemination, is planned for a later release once Votor is adopted and has not yet been scheduled.

A one-slot handoff after five months of rehearsals

The migration feature activates at the start of epoch 1064. Anza initially pointed to around 14:50 UTC on Oct. 21, or about 11:50 p.m. KST. Because epoch start times shift with block production speed, Solana's official upgrade page now estimates the epoch will begin around 10:20 p.m. KST on Oct. 21. The network will keep running TowerBFT for about 18 minutes before blocks stop carrying user transactions from slot 459,653,000. Once a block backed by 82% of stake is designated as Alpenglow's genesis block, later blocks are rolled back and user transactions resume under the new system. Anza said the handoff takes a few hundred milliseconds and that no user-signed transactions are lost in the process.

Anza rehearsed for five months on a community validator cluster. It ran nine successful migrations at scale and also simulated the switch across 1,500 nodes. The bug bounty exceeds 25,000 SOL. Validators must run version 4.3.2 of Agave, Jito-Solana or Harmonic Salsa, and Firedancer-based clients are not supported during the migration. Instead of vote fees, validators pay a 0.8 SOL Validator Admission Ticket (VAT) each epoch from their vote accounts.

SOL trades at 141,100 won on Upbit ahead of the switch

As of 3:32 p.m. KST on Oct. 21, SOL traded at 141,100 won on Upbit's Korean won market. At the same time it was $106.14 on Binance, up 1.4% from 24 hours earlier. Upbit's price was 0.17% above the overseas price converted into won (about 140,866 won), a small kimchi premium (the gap between prices on Korean exchanges and global markets). Upbit's 24-hour trading value was about 18.5 billion won. SOL's 52-week high on Upbit was 303,300 won on Oct. 27, 2025, and its low was 91,800 won on June 6 this year.