HalcyonHook on Ethereum

Uniswap v4 Hook Contract 0x313ea55aa2df26138b1df5cf04fef6af030e98c0 on Ethereum · Launchpad · Verified contract

Volume (24h)
$128
Value locked (TVL)
$4.69K
All-time volume
$783.72K
Pools using this hook
18
Swaps (24h)
9 (5 traders)
Total swaps
3,981

What it does

A Halcyon launchpad hook where early buyers pay a launch fee falling from up to 90% to 1% within a day, sellers pay a fixed 1% to 5%, buys otherwise pay 1%, and only the locker can provide liquidity.

How it works step by step

  • Serves Halcyon launchpad pools (ETH paired with a new coin) and only allows pools the launchpad has prepared.
  • Charges a launch anti-sniper fee on buys that starts as high as the creator chose (up to 90%) and falls in a straight line to 1% over a window of up to 1 day.
  • Charges a permanent sell fee chosen by the creator between 1% and 5%; buys pay 1% after the launch window.
  • During the launch window, caps how many coins a single swap can receive (if the creator set a cap).
  • Only the Halcyon locker contract can add liquidity, so all pool fees go to the locked position.
Swap behaviour
Each swap gets a fee override: buys pay a decaying launch fee (up to 90% at launch, down to 1% by the end of the window), then 1%; sells pay the creator-set 1% to 5%. During the window, a swap that receives more coins than the per-swap cap reverts.
Liquidity behaviour
Only the Halcyon locker can add liquidity; anyone else's add reverts. The hook never runs on withdrawals, but liquidity is held by the locker contract rather than individual LPs.
Fee behaviour
LP fee is 1% on buys after launch, 1% to 5% on sells (fixed per pool), and up to 90% on early buys decaying linearly to 1% within at most 1 day. All fees go to the pool's liquidity position held by the Halcyon locker.
Owner & admin controls
The launchpad (looked up from the fees contract) sets each pool's rules once before launch within the caps (launch fee up to 90%, sell fee 1% to 5%, window up to 1 day), and can toggle an exemption that gives a pool base 1% fees and no swap cap. Rules cannot be changed after preparation except the exempt flag.

Enabled Uniswap v4 callbacks

afterInitialize, beforeAddLiquidity, beforeSwap, afterSwap

afterInitialize: records launch start time and checks the pool was prepared by the launchpad; beforeAddLiquidity: restricts adding liquidity to the locker; beforeSwap: sets the dynamic buy/sell fee; afterSwap: enforces the per-swap max during the launch window.

Security & trust assessment

Risk level: medium (verified source, high confidence).

Who controls it: The launchpad address, resolved through an external fees contract, configures pool rules once and can toggle a fee/cap exemption. It cannot raise fees above the hard caps or touch pool funds.

Risk to user funds: The hook holds no funds and cannot take tokens via deltas; traders pay 1% to 5% normally and up to 90% on buys during the launch window of at most 1 day. Withdrawals are never blocked by the hook, though liquidity belongs to the locker.

Security findings

  • [medium] High launch fee on early buys: Buys right after launch can pay up to 90%, decaying linearly to 1% over at most 1 day; this is a disclosed anti-sniper mechanism, bounded in time.
  • [low] Launchpad-controlled exemption: The launchpad can toggle an exempt flag at any time, giving everyone the 1% base fee and lifting the swap cap; it cannot raise fees.
  • [info] Single locked liquidity provider: Only the locker can add liquidity, so public LPs cannot participate; withdrawals are not hooked.
  • [info] Fixed sell fee cap: Sell fees are fixed per pool between 1% and 5% and cannot be changed after preparation.

Contract details

Verified source
Yes (HalcyonHook)
Compiler
solc 0.8.28+commit.7893614a
Bytecode size
6,126 bytes
Upgradeable proxy
No
Detected patterns
launchpad

Pools using HalcyonHook