Solana validators can now hand the ordering of their blocks to competing builders. Gravity Block Exchange (GBX), an open marketplace for Solana blockspace, went live on mainnet on 11 November 2026, with two block builders competing for the slots of every validator connected to it. Builder firms Astralane and Gattaca each said GBX is already running on validators that hold 5% of Solana's stake.
A block builder is the software that picks which pending transactions go into a block and in what order. That order decides who gets filled first in a busy market, and how much the validator earns in fees and tips for producing the block. On GBX, builders compete for that job round by round, and the validator takes whichever sequence pays it most.
How the GBX auction works inside a Solana slot
GBX splits each leader slot, the short window in which one validator produces the block, into auction rounds, according to the GBX architecture docs. Incoming transactions stream to every connected builder through the slot. Each builder submits a candidate sequence built from the latest flow, and at the round deadline GBX forwards the submission with the highest reward for the validator.
The losing builders then receive the sequence that was executed, update their own view of the chain, and compete again in the next round. A finished block is stitched together from the winners of many rounds. GBX says every submission is scored the same way, by the rewards it produces for the validator, with no preference for any builder, and the auction keeps running if one builder is slow or offline.
The validator gives up only the ordering. It still verifies and executes transactions, votes and broadcasts the block to the network, the docs say.
What Solana validators need to run the Gravity Connector
Validators join through the Gravity Connector, an open-source sidecar program released under Apache-2.0 and MIT licences. It runs as a separate process beside the validator, so operators keep their usual client with no custom fork to maintain. The repository supports Anza's Agave client and Jito JTO$0.318-5.1%'s Jito-Solana client at version 4.3 on its main branch, with 4.4 on a separate branch.
The GBX setup guide asks operators for:
- one CPU core dedicated to the Connector, which runs it at about full load
- scheduler bindings switched on in the validator
- access to the validator's ledger directory and identity keypair
- an outbound connection to one of GBX's relays in Amsterdam, Frankfurt, London or Tokyo
Access is granted per validator: operators send the Gravity team their identity key, client version and region. If the external sequencing path goes down, the Connector steps out of the way and the validator falls back to its own scheduler, so a GBX outage does not stop block production. Validators running Jito-Solana point their block-engine traffic at a local proxy inside the Connector while it is active. Support for the Firedancer validator client is in development.
Bifrost and Titan Builder: the first two competing block builders
Astralane said its own builder, Bifrost, "is in every auction", calling GBX "one set of rules for all". A day earlier Astralane had posted that "Solana has had only two block builders", alongside a summit talk on what it takes to build the next one.
Gattaca wrote that Solana needs an open, competitive market for sequencing that gets validators the most value from their blockspace and improves execution for users, and that GBX brings competitive building to Solana. The firm announced that its Titan Builder was live from day one, "building blocks and competing in every auction". Titan Builder's Solana documentation shows what that means for traders and bots that send it transactions:
- bundles of up to five signed transactions, sent to endpoints in the same four regions as GBX's relays
- a minimum tip of 5,000 lamports, with higher tips getting higher priority
- bundles land only in the slots of validators connected to GBX
The interface definitions sit in a public repository under Gattaca's GitHub organisation.
How multi-builder auctions compare with Jito, Harmonic and Flowra
GBX joins a busy field. Searchers, the bots that hunt for MEV (the extra value from ordering transactions well), already send tipped bundles of trades to Jito's block engine. GBX does not ask validators to drop that setup: Jito-Solana operators keep their client and route block-engine traffic through the Connector.
Other newcomers have taken narrower routes. Temporal's Harmonic marketplace opened a backrun-only searcher network to public beta on 5 November with identity-checked searchers, and Seoul-based Flowra launched an open orderflow auction for Solana block building in August. GBX's design point is different from both: several whole builders compete for each round of a slot under one published scoring rule.
The prize is the fee and tip revenue that block ordering decides. In epoch 1083, which ended on 10 November 2026, priority fees came to about 5,500 SOL and Jito tips about 1,700 SOL, together roughly 10% of the 69,800 SOL earned by validators and stakers that epoch, according to Solana Compass reward data. Newly issued SOL made up nearly all of the rest.
Day to day, priority fees outweigh tips. Over the 14 days to 11 November, Solana Compass fee data shows about 60,000 SOL in priority fees against about 23,000 SOL in Jito tips.
Priority fees, which go to the block's leader, ran about 2.6 times Jito tips over the two weeks to 11 November, the revenue that block ordering decides.
View on Solana Compass →For delegators, the gain from a better-built block depends on what their validator passes on. Priority fees go to the block's leader by default, while Jito tips are shared with stakers after the validator's MEV commission. Our hub explains how each kind of reward reaches a delegator, and Solana Compass's tool lets holders collect the Jito tips that build up in their stake accounts without unstaking.
What to watch as Solana block building opens up
The launch figure of 5% comes from the builders taking part. Several things will show whether competitive building spreads on Solana:
- Firedancer support, which would open GBX to validators on that client
- a third builder joining Bifrost and Titan Builder
- whether GBX opens access beyond request-based onboarding, and on what terms for validators and builders
- reward figures from connected validators that others can check against on-chain data
Astralane said more details on Bifrost are coming soon.
