fix: getLiquidityParams: int256 overflow on large VWAP values (#622)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

onchain/src/Optimizer.sol

@@ -414,6 +414,7 @@ contract Optimizer is Initializable, UUPSUpgradeable, IOptimizer {
             // ---- Slot 2: pricePosition (also needs VWAP) ----
             if (vwapTracker != address(0)) {
                 uint256 vwapX96 = IVWAPTracker(vwapTracker).getVWAP();
+                require(vwapX96 <= uint256(type(int256).max), "VWAP exceeds int256 range");
                 if (vwapX96 > 0) {
                     // Convert pool tick to KRK-price space: higher tick = more expensive KRK.
                     // Uniswap convention: tick ↑ → token1 more expensive relative to token0.

onchain/test/Optimizer.t.sol

@@ -704,3 +704,78 @@ contract OptimizerNormalizedInputsTest is Test {
 
 import { TickMath } from "@aperture/uni-v3-lib/TickMath.sol";
 import { Math } from "@openzeppelin/utils/math/Math.sol";
+
+// =============================================================================
+// VWAP int256 overflow guard test (issue #622)
+// =============================================================================
+
+/// @dev Minimal mock that returns a configurable VWAP value for overflow testing.
+contract ConfigurableVWAPMock {
+    uint256 private _vwap;
+
+    function setVWAP(uint256 v) external {
+        _vwap = v;
+    }
+
+    function getVWAP() external view returns (uint256) {
+        return _vwap;
+    }
+}
+
+contract OptimizerVWAPOverflowTest is Test {
+    OptimizerInputCapture capture;
+    Optimizer optimizer;
+    MockStake mockStake;
+    MockKraiken mockKraiken;
+    ConfigurableVWAPMock configurableVwap;
+    MockPool mockPool;
+
+    function setUp() public {
+        mockKraiken = new MockKraiken();
+        mockStake = new MockStake();
+        configurableVwap = new ConfigurableVWAPMock();
+        mockPool = new MockPool();
+
+        OptimizerInputCapture impl = new OptimizerInputCapture();
+        bytes memory initData = abi.encodeWithSelector(Optimizer.initialize.selector, address(mockKraiken), address(mockStake));
+        ERC1967Proxy proxy = new ERC1967Proxy(address(impl), initData);
+        capture = OptimizerInputCapture(address(proxy));
+        optimizer = Optimizer(address(proxy));
+
+        optimizer.setDataSources(address(configurableVwap), address(mockPool), address(0), false);
+        mockPool.setCurrentTick(0);
+        mockPool.setRevertOnObserve(true);
+    }
+
+    /// @notice VWAP value exceeding int256.max must revert with descriptive message.
+    function testRevertsWhenVWAPExceedsInt256Max() public {
+        configurableVwap.setVWAP(uint256(type(int256).max) + 1);
+
+        vm.expectRevert("VWAP exceeds int256 range");
+        optimizer.getLiquidityParams();
+    }
+
+    /// @notice VWAP at exactly int256.max should not revert.
+    function testAcceptsVWAPAtInt256Max() public {
+        configurableVwap.setVWAP(uint256(type(int256).max));
+
+        // Should not revert
+        optimizer.getLiquidityParams();
+    }
+
+    /// @notice VWAP at uint256.max must revert.
+    function testRevertsWhenVWAPIsUint256Max() public {
+        configurableVwap.setVWAP(type(uint256).max);
+
+        vm.expectRevert("VWAP exceeds int256 range");
+        optimizer.getLiquidityParams();
+    }
+
+    /// @notice VWAP of zero should not revert (no-op path).
+    function testAcceptsVWAPZero() public {
+        configurableVwap.setVWAP(0);
+
+        // Should not revert — zero VWAP skips the pricePosition computation
+        optimizer.getLiquidityParams();
+    }
+}