Approved workflow

Release Last Buyer (token symbol LBUY) on Sepolia as a univ4_hook launch. Token: Last Buyer (LBUY), total supply 1,000,000,000 LBUY with 18 decimals, minted once to the deployer. Hook: LastBuyerJackpotHook, a Uniswap v4 hook on the token's native-ETH pool. Deployment: the constructor takes one argument, the Sepolia PoolManager 0xE03A1074c86CFeDd5C142C4F04F1a1536e203543, passed as a literal in launch.json constructorArgs; getHookPermissions() returns exactly afterSwap and afterSwapReturnDelta and every other flag false (address bits 0x0044 under mask 0x3FFF), validated in the constructor; the factory mines the CREATE2 salt. The factory's pool is currency0 = native ETH, currency1 = LBUY, LP fee 3000, tickSpacing 60, seeded with LBUY only, so the first buy lands in a pool holding no ETH and must work. State is keyed by PoolId; pools whose currency0 is not native ETH get zero deltas and no state. Callbacks are PoolManager-only (override BaseHook's internal _before/_after functions). No owner, admin, pause or upgrade path. Tests swap through a real PoolManager; the Identity-md/univ4hook-start-template harness (BaseHookTest) provides the launch pool. A Sepolia test toy with no value; say so on the site. Behaviour: every exact-input buy (zeroForOne, amountSpecified < 0) pays 1% (100 bps, floor) of its LBUY output into the pool's jackpot: afterSwap returns that fee as a positive hookDeltaUnspecified and settles it by minting the hook ERC-6909 claims (poolManager.mint(address(this), currency1.toId(), fee)), so the jackpot is held as LBUY claims at the PoolManager, as the context requires. Sells and exact-output buys pay nothing and change nothing. A buy qualifies for the round when |amountSpecified| >= 0.001 ETH and hookData is exactly 32 bytes that abi-decode to a non-zero address: that address becomes lastBuyer and lastBuyAt = block.timestamp. Any other hookData (empty, wrong length, zero address) never reverts the swap; the buy still pays the fee but does not qualify. As the context requires, there is no fallback to the router sender: a router cannot claim. hookData is unauthenticated, so a buyer may name any address; that only gifts the round to that address. For wallets, the hook also offers buy(PoolKey key, uint256 minOut) payable: an exact-input buy of msg.value through poolManager.unlock that passes abi.encode(msg.sender) as hookData (so the buyer is authenticated on this path), settles the ETH it spent, refunds any unspent ETH, sends the LBUY to msg.sender and reverts if it receives less than minOut. claim(PoolKey key): anyone, once lastBuyer != 0 and block.timestamp >= lastBuyAt + 3,600; resets jackpot and lastBuyer and increments the round first, then through poolManager.unlock burns the jackpot's claims and takes that LBUY to lastBuyer. With no qualifying buy the jackpot simply grows. Views: jackpot(poolId), lastBuyer(poolId), lastBuyAt(poolId), round(poolId), claimableAt(poolId). Events: JackpotFed(poolId, amount), NewLeader(poolId, buyer, round), JackpotClaimed(poolId, winner, amount, round). Tests must show: the fee on exact-input buys only, qualification for each hookData shape and the 0.001 ETH edge, the timer at 3,599 and 3,600 seconds, a buy in the claim block resetting the timer, claim paying lastBuyer whoever calls, buy() with minOut, and the invariant PoolManager.balanceOf(hook, currency1 id) == sum of jackpots. The independent adversarial review must attack: hookData decoding (a malformed payload must not brick swaps), delta sign, spoofed buyers, claim timing races, buy() and claim() settlement in the unlock callback (which must tell the two apart), and any way to drain the jackpot. Then a small website that shows the jackpot in LBUY, the last buyer, the countdown, a buy form that calls buy() (ETH amount, slippage-based minOut) and a claim button. Read state from hook views and events via a public Sepolia RPC with no backend; keep it to one small page; the static export has index.html in dist/.

Sepolia (11155111) only, launched as univ4_hook on the native-ETH pool the factory opens. GitHub publication and IPFS hosting are approved. Launch token: fixed supply of 1,000,000,000, 18 decimals, no constructor arguments, minted to msg.sender, no mint or admin. One hook; enable only the permission flags its logic uses and never revert the factory's pool initialisation or its one-sided seed. Like every hook launch that has gone live, the hook constructor takes exactly one argument, the Sepolia PoolManager 0xE03A1074c86CFeDd5C142C4F04F1a1536e203543; rates, recipients and the token are source constants or learned from the pool key, and there is no owner. Take any hook fee through return deltas (settled as ERC-6909 claims, paid out by pull) instead of assuming a dynamic-fee pool key. Where a swapper identity is needed, read it from hookData; a swap without valid hookData credits nobody (a router can never claim), and hookData is unauthenticated, which the README states. No external oracles or VRF, no proxies, delegatecall or selfdestruct. foundry.toml sets bytecode_hash = "none". Any website is a static export with index.html in dist/. Site label lab-jackpot-hook.

Build LBUY and LastBuyerJackpotHook (afterSwap + afterSwapReturnDelta; 1% of each exact-input buy's LBUY output feeds a last-buyer jackpot, identity from hookData or the hook's own buy()) with tests against a real PoolManager and an independent review, deploy them, then build the website against the live pool.

Jackpot, last buyer, countdown, a buy form through the hook's buy() and a claim button.