What are Solvers?
Market makers that front their own capital to fill intents in seconds, and are reimbursed at settlement.
In the Nexus protocol, solvers are professional market makers that supply liquidity on the destination chain to fill user intents.
Once the user's funds are deposited into the Vault contracts on the source chains, a solver fronts its own capital on the destination chain and fills the intent — this is why users receive funds in seconds, without waiting for cross-chain finality.
The solver takes on the fill and is made whole afterwards: the protocol settles with solvers who have completed intents, releasing the user's locked source-chain funds to them through an on-chain settlement. Settlements are authorized by Nexus validators — the network settles on a sovereign rollup sequenced on Avail DA, where validators independently re-execute and verify state, and sign settlements with threshold signatures.
Currently, Avail runs the solvers for Nexus, but the solver network will be progressively decentralized in time. In a decentralized setup, multiple solvers compete to fill published intents, and competition keeps solver fees low.
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Fill here means the action of the solver providing the liquidity to the user, basically "filling" the intent's request for funds.