diff --git a/src/list.js b/src/list.js
index 3ebb622..78f3aa7 100644
--- a/src/list.js
+++ b/src/list.js
@@ -1,12 +1,14 @@
 import { Component, NewState, Util, Hash } from '@web/state'
 
-export const VirtualScroll = () => {
+export const VirtualScroll = (options = {}) => {
 	const itemHeights = new Map()
 	const groupHeights = new Map()
 	let groupItemCount = 1
 	const avg = Util.newAvg()
 	let padTop = 0, rowGap = 0, topMargin = 0, itemMarginTop = null, itemMarginBottom = null, listInited = false
 
+	const providedItemHeight = options.itemHeight || null;
+
 	return {
 		reset: (list, container) => {
 			listInited = false; itemHeights.clear(); groupHeights.clear(); avg.clear(); topMargin = 0; itemMarginTop = null; itemMarginBottom = null;
@@ -14,12 +16,33 @@ export const VirtualScroll = () => {
 			const size = list.length; groupItemCount = Math.ceil(Math.sqrt(size)) || 10;
 			const style = window.getComputedStyle(container);
 			padTop = parseFloat(style.paddingTop) || 0; rowGap = parseFloat(style.rowGap) || 0;
-			return list.slice(0, Math.min(30, size));
+			// Optimization: Give a reasonably large initial buffer instead of just 30 to prevent the
+			// "first scroll unresponsiveness" where the user scrolls past the small initial slice
+			// before the init() callback has time to map all heights.
+			const visibleCount = Math.max(10, Math.ceil((container.clientHeight || 100) / (providedItemHeight || 32)));
+			return list.slice(0, Math.min(visibleCount * 3, size));
 		},
 		init: (list, refreshCallback) => {
 			if (listInited) return;
-			const size = list.length, defaultHeight = avg.get() || 32;
-			for (let i = 0; i < size; i++) if (!itemHeights.has(i)) itemHeights.set(i, defaultHeight);
+			const size = list.length;
+			let defaultHeight = providedItemHeight || avg.get() || 32;
+			
+			// Optimization: If the first item declares a fixed height, use it as the global baseline.
+			// This completely bypasses the need for DOM measurement (node.offsetHeight) in fixed-height scenarios.
+			if (size > 0 && typeof list[0] === 'object' && list[0] !== null && list[0]._itemHeight) {
+				defaultHeight = list[0]._itemHeight;
+			}
+			
+			avg.add(defaultHeight);
+			if (itemMarginTop === null) { itemMarginTop = 0; itemMarginBottom = 0; }
+
+			for (let i = 0; i < size; i++) {
+				if (!itemHeights.has(i)) {
+					// Fallback to individual item height if specified, otherwise global default
+					const ih = (typeof list[i] === 'object' && list[i] !== null && list[i]._itemHeight) ? list[i]._itemHeight : defaultHeight;
+					itemHeights.set(i, ih);
+				}
+			}
 			for (let i = 0; i < size; i += groupItemCount) groupHeights.set(i, Math.min(groupItemCount, size - i) * defaultHeight);
 			listInited = true; refreshCallback();
 		},