diff --git a/tools/sprite-generation/gui/src/pages/SpriteTheaterPage.tsx b/tools/sprite-generation/gui/src/pages/SpriteTheaterPage.tsx
index a16ce001..b7d55773 100644
--- a/tools/sprite-generation/gui/src/pages/SpriteTheaterPage.tsx
+++ b/tools/sprite-generation/gui/src/pages/SpriteTheaterPage.tsx
@@ -21,6 +21,7 @@ const MIN_CARD_WIDTH = 220
 const GRID_GAP = 12
 const GRID_PADDING = 16
 const FALLBACK_INFO_HEIGHT = 68
+const HEADER_HEIGHT = 49
 
 const CARD_ENTER_MS = 400
 const CARD_SHIFT_MS = 300
@@ -71,38 +72,54 @@ interface GridDims {
 
 function useGridDimensions(
   containerRef: RefObject<HTMLDivElement | null>,
+  cardRefs: RefObject<Map<number, HTMLDivElement>>,
   onResize: () => void,
-): GridDims {
+): GridDims & { recompute: () => void } {
   const [dims, setDims] = useState<GridDims>({ cols: 0, rows: 0, cardWidth: 0 })
   const onResizeRef = useRef(onResize)
   onResizeRef.current = onResize
+  const measuredCardHeight = useRef(0)
+
+  const compute = useCallback((): void => {
+    const el = containerRef.current
+    if (!el) return
+
+    const rect = el.getBoundingClientRect()
+    const usableW = rect.width - 2 * GRID_PADDING
+    const usableH = rect.height - 2 * GRID_PADDING
+    if (usableW <= 0 || usableH <= 0) return
+
+    const cols = Math.max(1, Math.floor((usableW + GRID_GAP) / (MIN_CARD_WIDTH + GRID_GAP)))
+    const cardWidth = (usableW - (cols - 1) * GRID_GAP) / cols
+
+    // Measure actual card height from a rendered card if available
+    const firstCard = cardRefs.current?.values().next().value as HTMLDivElement | undefined
+    if (firstCard) {
+      measuredCardHeight.current = firstCard.getBoundingClientRect().height
+    }
+    const cardHeight = measuredCardHeight.current > 0
+      ? measuredCardHeight.current
+      : cardWidth + FALLBACK_INFO_HEIGHT
+
+    const rows = Math.max(1, Math.floor((usableH + GRID_GAP) / (cardHeight + GRID_GAP)))
+    setDims(prev => {
+      if (prev.cols === cols && prev.rows === rows && Math.abs(prev.cardWidth - cardWidth) < 1) return prev
+      return { cols, rows, cardWidth }
+    })
+    onResizeRef.current()
+  }, [containerRef, cardRefs])
 
   useEffect(() => {
     const el = containerRef.current
     if (!el) return
 
-    const compute = (): void => {
-      const rect = el.getBoundingClientRect()
-      const usableW = rect.width - 2 * GRID_PADDING
-      const usableH = rect.height - 2 * GRID_PADDING
-      const cols = Math.max(1, Math.floor((usableW + GRID_GAP) / (MIN_CARD_WIDTH + GRID_GAP)))
-      const cardWidth = (usableW - (cols - 1) * GRID_GAP) / cols
-      const cardHeight = cardWidth + INFO_HEIGHT
-      const rows = Math.max(1, Math.floor((usableH + GRID_GAP) / (cardHeight + GRID_GAP)))
-      setDims(prev => {
-        if (prev.cols === cols && prev.rows === rows && Math.abs(prev.cardWidth - cardWidth) < 1) return prev
-        return { cols, rows, cardWidth }
-      })
-      onResizeRef.current()
-    }
-
     const ro = new ResizeObserver(compute)
     ro.observe(el)
     compute()
     return () => ro.disconnect()
-  }, [containerRef])
+  }, [containerRef, compute])
 
-  return dims
+  return { ...dims, recompute: compute }
 }
 
 /* ── score badge ───────────────────────────────────────────────── */
@@ -129,10 +146,9 @@ interface CardProps {
   v: RecentVariant
   isNew: boolean
   index: number
-  cardWidth: number
 }
 
-const Card = memo(forwardRef<HTMLDivElement, CardProps>(function Card({ v, isNew, index, cardWidth }, ref) {
+const Card = memo(forwardRef<HTMLDivElement, CardProps>(function Card({ v, isNew, index }, ref) {
   const labeled = isLabeled(v)
   const conf = useMemo(() => confidence(v), [v.notes])
   const scores = useMemo(() => parseScores(v.notes), [v.notes])
@@ -164,7 +180,6 @@ const Card = memo(forwardRef<HTMLDivElement, CardProps>(function Card({ v, isNew
         border: cardBorder,
         position: 'relative',
         boxShadow: cardShadow,
-        width: cardWidth,
         willChange: 'transform',
         ...animStyle,
       }}
@@ -241,11 +256,9 @@ const Card = memo(forwardRef<HTMLDivElement, CardProps>(function Card({ v, isNew
 function LeavingCard({
   v,
   rect,
-  cardWidth,
 }: {
   v: RecentVariant
   rect: DOMRect
-  cardWidth: number
 }): ReactNode {
   return (
     <div
@@ -259,7 +272,7 @@ function LeavingCard({
         animation: `fadeOut ${FADE_OUT_MS}ms ease forwards`,
       }}
     >
-      <Card v={v} isNew={false} index={0} cardWidth={cardWidth} />
+      <Card v={v} isNew={false} index={0} />
     </div>
   )
 }
@@ -302,9 +315,37 @@ export default function SpriteTheaterPage(): ReactNode {
   variantsRef.current = variants
 
   const onResize = useCallback(() => { isResizeRef.current = true }, [])
-  const { cols, rows, cardWidth } = useGridDimensions(gridRef, onResize)
-  const visibleCount = cols * rows
+  const { cols, rows, recompute } = useGridDimensions(gridRef, cardRefs, onResize)
   const getCardRef = useCardRefCallbacks(cardRefs)
+  const hasRecomputedRef = useRef(false)
+  const [loadedRows, setLoadedRows] = useState(0)
+  const sentinelRef = useRef<HTMLDivElement>(null)
+  const totalCountRef = useRef(0)
+
+  // Reset loaded rows when viewport rows change (resize), seed with viewport fit
+  useEffect(() => {
+    if (rows > 0) setLoadedRows(rows)
+  }, [rows])
+
+  // Lazy-load more rows when sentinel enters viewport
+  useEffect(() => {
+    const sentinel = sentinelRef.current
+    if (!sentinel || cols === 0) return
+
+    const io = new IntersectionObserver(
+      (entries) => {
+        if (entries[0].isIntersecting) {
+          const totalRows = Math.ceil(totalCountRef.current / cols)
+          setLoadedRows(prev => Math.min(prev + rows, totalRows))
+        }
+      },
+      { root: gridRef.current, rootMargin: '200px' },
+    )
+    io.observe(sentinel)
+    return () => io.disconnect()
+  }, [cols, rows])
+
+  const visibleCount = cols > 0 ? loadedRows * cols : 20
 
   // Clear "new" flags after animation
   useEffect(() => {
@@ -320,6 +361,13 @@ export default function SpriteTheaterPage(): ReactNode {
     return () => clearTimeout(timer)
   }, [leaving])
 
+  // Recompute grid once actual card height is measurable
+  useEffect(() => {
+    if (hasRecomputedRef.current || cardRefs.current.size === 0) return
+    hasRecomputedRef.current = true
+    requestAnimationFrame(recompute)
+  }, [variants, recompute])
+
   // Capture current rects before state update
   const captureRects = useCallback((): void => {
     const rects = new Map<number, DOMRect>()
@@ -360,14 +408,18 @@ export default function SpriteTheaterPage(): ReactNode {
 
   // Memoize sorted + visible to prevent effect re-fire
   const sorted = useMemo(
-    () => [...variants].sort((a, b) =>
-      new Date(b.created_at).getTime() - new Date(a.created_at).getTime()
-    ),
+    () => {
+      const s = [...variants].sort((a, b) =>
+        new Date(b.created_at).getTime() - new Date(a.created_at).getTime()
+      )
+      totalCountRef.current = s.length
+      return s
+    },
     [variants],
   )
 
   const visible = useMemo(
-    () => visibleCount > 0 ? sorted.slice(0, visibleCount) : sorted.slice(0, 20),
+    () => sorted.slice(0, Math.min(visibleCount, sorted.length)),
     [sorted, visibleCount],
   )
 
@@ -486,7 +538,7 @@ export default function SpriteTheaterPage(): ReactNode {
         </div>
         <div style={{ display: 'flex', alignItems: 'center', gap: 16 }}>
           <span style={{ fontSize: 11, color: colors.muted }}>
-            {cols}&times;{rows} grid &middot; {visibleCount} visible
+            {cols}&times;{rows} grid &middot; {visible.length}/{sorted.length}
           </span>
           <a href="/" style={{ color: colors.muted, textDecoration: 'none', fontSize: 13 }}>
             Dashboard
@@ -494,24 +546,32 @@ export default function SpriteTheaterPage(): ReactNode {
         </div>
       </div>
 
-      {variants.length === 0 ? (
-        <div style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center' }}>
-          <div style={{ textAlign: 'center', color: colors.muted }}>
-            <div style={{ fontSize: 48, marginBottom: 16 }}>Waiting for sprites...</div>
-            <div>Generate sprites with <code style={{ color: colors.text }}>./run tools spritegen generate</code></div>
-            <div style={{ marginTop: 8 }}>New images will appear here in real-time</div>
+      <div
+        ref={gridRef}
+        style={{
+          flex: 1,
+          overflowY: 'auto',
+          overflowX: 'hidden',
+          padding: GRID_PADDING,
+          boxSizing: 'border-box',
+          position: 'relative',
+        }}
+      >
+        {variants.length === 0 ? (
+          <div style={{
+            position: 'absolute',
+            inset: 0,
+            display: 'flex',
+            alignItems: 'center',
+            justifyContent: 'center',
+          }}>
+            <div style={{ textAlign: 'center', color: colors.muted }}>
+              <div style={{ fontSize: 48, marginBottom: 16 }}>Waiting for sprites...</div>
+              <div>Generate sprites with <code style={{ color: colors.text }}>./run tools spritegen generate</code></div>
+              <div style={{ marginTop: 8 }}>New images will appear here in real-time</div>
+            </div>
           </div>
-        </div>
-      ) : (
-        <div
-          ref={gridRef}
-          style={{
-            flex: 1,
-            overflow: 'hidden',
-            padding: GRID_PADDING,
-            boxSizing: 'border-box',
-          }}
-        >
+        ) : (
           <div style={{
             display: 'grid',
             gridTemplateColumns: cols > 0 ? `repeat(${cols}, 1fr)` : `repeat(auto-fill, minmax(${MIN_CARD_WIDTH}px, 1fr))`,
@@ -525,19 +585,21 @@ export default function SpriteTheaterPage(): ReactNode {
                 v={v}
                 isNew={newIds.has(v.variant_id)}
                 index={i}
-                cardWidth={cardWidth > 0 ? cardWidth : MIN_CARD_WIDTH}
               />
             ))}
           </div>
-        </div>
-      )}
+        )}
+        {/* Sentinel — triggers lazy loading of next batch of rows */}
+        {visible.length < sorted.length && (
+          <div ref={sentinelRef} style={{ height: 1 }} />
+        )}
+      </div>
 
       {leaving.map(({ v, rect }) => (
         <LeavingCard
           key={`leave-${v.variant_id}`}
           v={v}
           rect={rect}
-          cardWidth={cardWidth > 0 ? cardWidth : MIN_CARD_WIDTH}
         />
       ))}
     </div>