Swap Against a StablePair Pool

Swapping against a StablePair pool uses the standard v4 swap path. The only difference is the fee: it is set by the hook at swap time, so it cannot be read from the pool key.

Build the pool key

The pool uses v4's dynamic fee flag rather than a fixed fee tier. Code that assumes a static tier will not find the pool.

PoolKey memory key = PoolKey({
    currency0: Currency.wrap(USDC),
    currency1: Currency.wrap(USDT),
    fee: LPFeeLibrary.DYNAMIC_FEE_FLAG, // 0x800000, not a fee tier
    tickSpacing: 1,
    hooks: IHooks(0x0000113dCf4ADd69999Fad8F20F2b63F979bfcC0)
});

Read the current fee

PoolKey.fee holds the dynamic flag, not a rate. Instead, the hook exposes a view function returning the exact LP fee a swap will be charged in the current block, per direction:

function getFee(PoolKey calldata key) external view returns (uint24 feeE6ZeroForOne, uint24 feeE6OneForZero);

Both values are returned in 1e6 precision, matching v4's own fee units.

For routers and aggregators this makes quoting substantially cheaper: the fee can be computed locally rather than simulated per size. Two properties are why.

• Size-independent. The fee never depends on the swap amount, so the same value applies to every size. getFee never reads a swap amount, and so never reverts on the basis of one.
• Fixed for the block. Both values are computed from the start-of-block price the next swap will see, so one read per pool per block covers every quote in that block. See Block Price Caching.

The two directions differ, often substantially (outside the band one of them is zero), so quote the direction being swapped.

getFee reverts with PoolNotInitialized if the pool was not initialized through the hook.

Execute the swap

Swap through the standard v4 router or PoolManager unlock flow. StablePair holds no return-delta permissions, so it never alters swap amounts. It only overrides the fee.

Where to Go Next

• Dynamic Fees
• Provide Liquidity on StablePair