Helius hSOL$107.66+0.2% opened its Solana preconfirmation stream to every paid plan on 16 October 2026. In a post at 23:06 UTC, Helius said preconfs "are now live for all paid plans" and listed four new filters for the preconfSubscribe WebSocket subscription: signer (include or exclude), signatures, instructions, and a source filter that picks Helius's own feed, BAM (Block Assembly Marketplace), or both. The preconfSubscribe docs now list the Developer, Business, Professional and Enterprise plans as eligible. Free plans are not.
When Helius launched preconfirmations on 22 July, the feature was "live now for Professional plans and above". Twelve weeks later, Developer and Business customers get the same stream.
What a Helius preconfirmation shows
A Helius preconfirmation is a message sent the moment a block leader commits to executing a transaction, before the transaction is packed into entries and cut into shreds, the small data packets Solana uses to spread a block across the network. Helius claims this arrives 5 to 50 milliseconds before shredding and calls it the earliest point a transaction can be observed on Solana. Both are Helius's own claims.
The stream draws on two sources. Helius emits messages from leaders that forward their execution stream to it, and those messages can report whether the transaction failed or succeeded. Helius also ingests signals from validators running BAM, the block-building marketplace from Jito JTO$0.346+3.8%, through Jito's regional endpoints, according to the Helius overview docs. BAM messages are sent when the validator commits to a transaction, before it runs, so they always report status "unknown." The new source filter lets a subscriber take one feed and skip the other.
Helius's docs call preconfirmations its lowest-latency transaction signal, earlier than its Shred Delivery product and processed-commitment streams. Helius followed the July launch with another early feed in August, preprocessedSubscribe, a pre-execution transaction stream.
preconfSubscribe filters and pricing
The four new filters narrow what a subscriber receives and pays for. Helius's docs cap signer filters at 10,000 addresses and signature filters at 1,000, and instruction filters match on program ID, data size or byte patterns. They sit alongside the existing account, region and failed-transaction filters.
Billing is per covered slot. A slot with no delivered messages costs nothing. When at least one message arrives, each open subscription is charged the greater of 300 credits or 10 credits per message, so 100 messages in one slot cost 1,000 credits, per the docs. Tighter filters mean fewer billable messages.
Preconfirmation limits: coverage gaps, no guarantee
Helius's docs say plainly that "a preconfirmation is an early signal, not a guarantee. The transaction has not yet landed onchain and could still be dropped." Coverage is partial too. Messages arrive only in slots led by a validator that forwards to Helius or runs BAM, and the docs tell developers to "expect slots with no messages." Helius pays validators to forward their preconfs to close those gaps, and the docs point traders to its Sender Max service (minimum tip 0.001 SOL) to act on what they see.
Jito's 9 October changelog put BAM at 164 million SOL across 385 validators, 37% of network stake as of epoch 1050, and said BAM validators "continue to earn 35% of preconfirmation revenue." That share lines up with our staking data, which shows about 443 million SOL actively staked in epoch 1050. By Jito's count, then, leaders holding close to two-thirds of stake sit outside BAM and appear in the stream only if they forward to Helius. Helius's overview gives BAM coverage of over 34% of stake at launch, near the level at which BAM preconfirmations went live.
BAM maintenance mode before Alpenglow
The same Jito changelog says "all mainnet BAM Nodes will be placed in Maintenance Mode during the days leading up to activation" of Alpenglow, the consensus switch Anza scheduled for about 14:50 UTC on 21 October, as we covered when the date was set. The changelog names two BAM-native features as unavailable in that period and says nodes return gradually after activation. Helius's docs do not say whether the BAM feed inside preconfSubscribe pauses during that window.
