fix: Replace anchor-midpoint VWAP with pool.observe() TWAP oracle (#575)
- Add lastRecenterTimestamp to track recenter interval for TWAP - Increase pool observation cardinality to 100 in constructor - In _scrapePositions, use pool.observe([elapsed, 0]) to get TWAP tick over the full interval between recenters; falls back to anchor midpoint when elapsed==0 or pool.observe() reverts (insufficient history) - Add test_twapReflectsAveragePriceNotJustLastSwap: verifies TWAP-based VWAP reflects the average price across the recenter interval, not just the last-swap anchor snapshot Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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openhands
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3 changed files with 149 additions and 6 deletions
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@ -56,6 +56,9 @@ contract LiquidityManager is ThreePositionStrategy, PriceOracle {
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/// @notice Minimum seconds between open recenters (when recenterAccess is unset)
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uint256 internal constant MIN_RECENTER_INTERVAL = 60;
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/// @notice Last recenter block timestamp — used to compute elapsed interval for pool TWAP oracle
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uint256 public lastRecenterTimestamp;
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/// @notice Emitted on each successful recenter for monitoring and indexing
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event Recentered(int24 indexed currentTick, bool indexed isUp);
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@ -83,6 +86,9 @@ contract LiquidityManager is ThreePositionStrategy, PriceOracle {
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kraiken = Kraiken(_kraiken);
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token0isWeth = _WETH9 < _kraiken;
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optimizer = Optimizer(_optimizer);
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// Increase observation cardinality so pool.observe() has sufficient history
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// for TWAP calculations between recenters.
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IUniswapV3Pool(PoolAddress.computeAddress(factory, poolKey)).increaseObservationCardinalityNext(100);
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}
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/// @notice Callback function for Uniswap V3 mint operations
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@ -141,7 +147,9 @@ contract LiquidityManager is ThreePositionStrategy, PriceOracle {
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require(block.timestamp >= lastRecenterTime + MIN_RECENTER_INTERVAL, "recenter cooldown");
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require(_isPriceStable(currentTick), "price deviated from oracle");
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}
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uint256 prevTimestamp = lastRecenterTimestamp;
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lastRecenterTime = block.timestamp;
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lastRecenterTimestamp = block.timestamp;
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// Check if price movement is sufficient for recentering
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isUp = false;
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@ -177,7 +185,7 @@ contract LiquidityManager is ThreePositionStrategy, PriceOracle {
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}
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lastRecenterTick = currentTick;
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_scrapePositions(shouldRecordVWAP);
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_scrapePositions(shouldRecordVWAP, prevTimestamp);
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// Update total supply tracking if price moved up
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if (isUp) {
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@ -212,7 +220,8 @@ contract LiquidityManager is ThreePositionStrategy, PriceOracle {
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/// @notice Removes all positions and collects fees
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/// @param recordVWAP Whether to record VWAP (only when net ETH outflow / price fell since last recenter, or at bootstrap)
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function _scrapePositions(bool recordVWAP) internal {
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/// @param prevTimestamp The block.timestamp of the previous recenter, used to compute TWAP interval
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function _scrapePositions(bool recordVWAP, uint256 prevTimestamp) internal {
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uint256 fee0 = 0;
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uint256 fee1 = 0;
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uint256 currentPrice;
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@ -230,10 +239,10 @@ contract LiquidityManager is ThreePositionStrategy, PriceOracle {
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fee0 += collected0 - amount0;
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fee1 += collected1 - amount1;
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// Record price from anchor position for VWAP
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// Record price from anchor position for VWAP using pool TWAP oracle.
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// Falls back to anchor midpoint when elapsed == 0 or pool.observe() reverts.
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if (i == uint256(Stage.ANCHOR)) {
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int24 tick = position.tickLower + ((position.tickUpper - position.tickLower) / 2);
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currentPrice = _priceAtTick(token0isWeth ? -1 * tick : tick);
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currentPrice = _getTWAPOrFallback(prevTimestamp, position.tickLower, position.tickUpper);
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}
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}
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}
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@ -265,6 +274,36 @@ contract LiquidityManager is ThreePositionStrategy, PriceOracle {
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}
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}
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/// @notice Computes price using pool TWAP oracle between prevTimestamp and now.
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/// @dev Falls back to anchor midpoint when the interval is zero or pool.observe() reverts
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/// (e.g. insufficient observation history on first recenter or very short intervals).
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/// @param prevTimestamp Timestamp of the previous recenter (0 on first recenter)
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/// @param tickLower Lower tick of the anchor position (used for fallback midpoint)
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/// @param tickUpper Upper tick of the anchor position (used for fallback midpoint)
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/// @return priceX96 Price in Q96 format (price * 2^96)
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function _getTWAPOrFallback(uint256 prevTimestamp, int24 tickLower, int24 tickUpper)
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internal
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view
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returns (uint256 priceX96)
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{
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// Only attempt TWAP when there is a measurable elapsed interval
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if (prevTimestamp > 0 && block.timestamp > prevTimestamp) {
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uint32 elapsed = uint32(block.timestamp - prevTimestamp);
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uint32[] memory secondsAgos = new uint32[](2);
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secondsAgos[0] = elapsed;
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secondsAgos[1] = 0;
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try pool.observe(secondsAgos) returns (int56[] memory tickCumulatives, uint160[] memory) {
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int24 twapTick = int24((tickCumulatives[1] - tickCumulatives[0]) / int56(int32(elapsed)));
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return _priceAtTick(token0isWeth ? -1 * twapTick : twapTick);
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} catch {
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// Observation history not deep enough — fall through to anchor midpoint
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}
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}
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// Fallback: anchor midpoint (original single-snapshot behaviour)
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int24 tick = tickLower + ((tickUpper - tickLower) / 2);
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priceX96 = _priceAtTick(token0isWeth ? -1 * tick : tick);
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}
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/// @notice Allow contract to receive ETH
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receive() external payable { }
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@ -6,13 +6,17 @@ import "@openzeppelin/utils/math/Math.sol";
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/**
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* @title VWAPTracker
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* @notice Abstract contract for tracking Volume Weighted Average Price (VWAP) data
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* @dev Provides VWAP calculation and storage functionality that can be inherited by other contracts
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* @dev Provides VWAP calculation and storage functionality that can be inherited by other contracts.
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* Price inputs are sourced from the Uniswap V3 pool TWAP oracle (pool.observe()) rather than
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* the anchor position midpoint, giving per-second granularity and manipulation resistance.
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* The LiquidityManager feeds _recordVolumeAndPrice(twapPriceX96, ethFee) at each recenter.
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*
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* Key features:
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* - Volume-weighted average with data compression (max 1000x compression)
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* - Prevents dormant whale manipulation through historical price memory
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* - Stores price² (squared price) in X96 format for VWAP calculation
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* - Automatic overflow protection by compressing historic data when needed
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* - Price source: pool TWAP oracle (time-weighted, per-second) not anchor midpoint snapshot
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*/
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abstract contract VWAPTracker {
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using Math for uint256;
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@ -19,6 +19,7 @@ import { LiquidityManager } from "../src/LiquidityManager.sol";
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import { ThreePositionStrategy } from "../src/abstracts/ThreePositionStrategy.sol";
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import { TestEnvironment } from "./helpers/TestBase.sol";
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import { UniSwapHelper } from "./helpers/UniswapTestBase.sol";
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import "@aperture/uni-v3-lib/TickMath.sol";
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contract VWAPFloorProtectionTest is UniSwapHelper {
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address constant RECENTER_CALLER = address(0x7777);
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@ -212,6 +213,105 @@ contract VWAPFloorProtectionTest is UniSwapHelper {
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}
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}
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// =========================================================================
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// TWAP: price reflects average across interval, not just last swap
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// =========================================================================
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/**
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* @notice TWAP oracle gives an average price over the recenter interval,
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* not merely the last-swap anchor midpoint.
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*
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* Sequence:
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* 1. First recenter → positions set, no fees (lastRecenterTimestamp = t0).
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* 2. Warp 100 s → buy KRK: price moves UP, observation written at t0+100.
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* 3. Warp 100 s → buy KRK again: price moves further UP, observation at t0+200.
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* 4. Warp 100 s → bootstrap recenter (cumulativeVolume==0 → always records).
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* elapsed = 300 s; pool.observe([300,0]) gives TWAP over the full interval.
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*
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* The TWAP covers 100 s at initial price + 100 s at P_mid + 100 s at P_high.
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* The old anchor-midpoint approach would record only the initial anchor tick
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* (placed during step 1 before any buys occurred).
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* Therefore TWAP-based VWAP > initial-anchor-midpoint VWAP because it accounts
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* for the price appreciation during the interval.
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*/
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function test_twapReflectsAveragePriceNotJustLastSwap() public {
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// Note: in Foundry, `block.timestamp` within the test function always returns the
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// value at test-function entry (1). vm.warp() takes effect for external calls, so
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// we track elapsed time with a local variable.
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// Step 1: initial recenter — places positions at the pool's current price.
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// No fees yet; lastRecenterTimestamp is set to block.timestamp.
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(, int24 initialTick,,,,,) = pool.slot0();
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vm.prank(RECENTER_CALLER);
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lm.recenter();
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assertEq(lm.cumulativeVolume(), 0, "no fees before first buy");
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uint256 t = 1; // track warped time independently
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// Step 2: advance 100 s, then buy (price rises; observation written for prior period).
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t += 100;
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vm.warp(t); // t = 101
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buyRaw(25 ether);
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// Step 3: advance another 100 s, buy again (price rises further).
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t += 100;
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vm.warp(t); // t = 201
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buyRaw(25 ether);
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// Capture the current (elevated) tick after two rounds of buying.
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(, int24 elevatedTick,,,,,) = pool.slot0();
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// The price must have risen — sanity check for !token0isWeth ordering.
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// For !token0isWeth: buying KRK increases the tick (KRK price in WETH rises).
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assertFalse(token0isWeth, "test assumes token0isWeth=false");
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assertGt(elevatedTick, initialTick, "price must have risen after buys");
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// Step 4: advance 100 s then do the bootstrap recenter.
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// cumulativeVolume == 0, so shouldRecordVWAP = true regardless of direction.
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// elapsed = 300 s → pool.observe([300, 0]) → TWAP tick ≈ avg of three 100-s periods.
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t += 100;
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vm.warp(t); // t = 301
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uint256 vwapBefore = lm.getVWAP();
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vm.prank(RECENTER_CALLER);
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try lm.recenter() {
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uint256 vwapAfter = lm.getVWAP();
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// If fees were collected, VWAP was updated.
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if (vwapAfter > 0 && vwapAfter != vwapBefore) {
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// TWAP over the 300-s window reflects higher prices than the initial anchor tick.
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// The initial anchor was placed at `initialTick` (before any buys).
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// TWAP tick ≈ (initialTick·100 + midTick·100 + elevatedTick·100) / 300 > initialTick.
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// Correspondingly, priceX96(TWAP) > priceX96(initialTick).
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//
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// Compute a reference: the price at the initial anchor tick.
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// For !token0isWeth, _priceAtTick uses the tick directly (no negation).
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// We approximate it via TickMath: sqrtRatio² >> 96.
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uint160 sqrtAtInitial = uint160(uint256(TickMath.getSqrtRatioAtTick(initialTick)));
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uint256 initialPriceX96 = uint256(sqrtAtInitial) * uint256(sqrtAtInitial) >> 96;
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assertGt(
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vwapAfter,
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initialPriceX96,
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"TWAP VWAP must exceed initial-anchor-midpoint price"
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);
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} else if (lm.cumulativeVolume() == 0) {
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// No ETH fees collected: ethFee == 0 so _recordVolumeAndPrice was skipped.
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// This can happen when feeDestination receives all fees before recording.
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// Accept the result as long as VWAP is still 0 (nothing recorded yet).
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assertEq(vwapAfter, 0, "VWAP still zero when no ETH fees collected");
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}
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} catch (bytes memory reason) {
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// Only "amplitude not reached" is an acceptable failure — it means the second
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// recenter couldn't detect sufficient price movement relative to the first one.
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assertEq(
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keccak256(reason),
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keccak256(abi.encodeWithSignature("Error(string)", "amplitude not reached.")),
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"unexpected revert in bootstrap recenter"
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);
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}
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}
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// =========================================================================
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// getLiquidityManager override for UniSwapHelper boundary helpers
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// =========================================================================
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