How it works

Bins

Liquidity sits in discrete bins, one price each, spaced a fixed step apart. Bin step 50 means each bin is 0.50 % above the one below it. A trade inside one bin has zero price impact; a trade that empties a bin moves the price one step to the next.

The active bin

The active bin is the one bin that holds both tokens and the one place a trade happens: the keystone. Every bin below it holds USDC only, every bin above it holds the token only. When a swap empties one side of the active bin, the next bin becomes active and the price moves one step.

Shapes

An LP picks a contiguous range of at most 120 bins and one of three shapes. Spot spreads the deposit evenly over the range. Curve piles it at the active bin and thins towards the edges, which is the arch above. Bid-Ask is heavy at both ends and thin in the middle. Auto-fill computes the paired amount from the active bin price; switching it off makes the deposit single-sided.

Fees

A swap pays the pool's LP fee plus a protocol fee. The LP fee is the base fee plus a variable part that rises with volatility and decays over time. Protocol fee 0.50 % of the input. Fees accrue to a separate claimable balance and do not compound. Fees vest 60 seconds after the last deposit. A deposit pays no fee, except 0.50 % on the part that lands in the active bin at a different composition than the bin's own.

Positions

A position is a range, a shape and the shares it holds in each bin. In range, it earns the pool's fees on every trade that prices its bins. Out of range earns nothing until the price returns to the range. Claim takes the fees. Withdraw takes the liquidity and the fees together.

Arc

Arc is Circle's USDC-native chain. USDC is the gas token and the quote of every pool, so every price on these screens is a USDC price and reads as dollars. Every pool is TOKEN / USDC. Creating a pool costs 5 USDC. Finality is under a second.

Contracts and transactions are on testnet.arcscan.app. Testnet USDC comes from faucet.circle.com.