How it works
Bins, the active bin, shapes, fees, positions, Arc, routing.
01 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.
02 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.
03 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.
04 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.
05 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.
06 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.
07 Routing
The Swap screen is a router. It quotes every venue on Arc that has a pool for the pair, ARCH bins among them, and takes the plan with the most output after each venue's own fees. Three venues in this version: ARCH, Uniswap v4 and Arcpools. USDC is the hub: a pair no venue serves directly goes through USDC in two hops, never three. Within a hop the input splits across up to three venues in whole 5 % steps, so a share always reads as a round number. ARCH bins are one venue, not the default: the screen prints what every venue alone would have paid, and the word best lands on the venue that won, or on the route when a split did.