diff --git a/packages/core/src/core.types.ts b/packages/core/src/core.types.ts
index 27214fb76..c3d069d31 100644
--- a/packages/core/src/core.types.ts
+++ b/packages/core/src/core.types.ts
@@ -19,8 +19,6 @@ export interface Asset {
 export type TimelineElementType = "video" | "image" | "text" | "audio" | "composition";
 export type MediaElementType = "video" | "image" | "audio";
 
-export type CanvasResolution = "landscape" | "portrait" | "landscape-4k" | "portrait-4k";
-
 export const CANVAS_DIMENSIONS = {
   landscape: { width: 1920, height: 1080 },
   portrait: { width: 1080, height: 1920 },
@@ -28,6 +26,15 @@ export const CANVAS_DIMENSIONS = {
   "portrait-4k": { width: 2160, height: 3840 },
 } as const;
 
+// Single source of truth: derive the type from the table so adding a preset
+// extends the union automatically. Avoids the prior `as readonly CanvasResolution[]`
+// cast on `VALID_CANVAS_RESOLUTIONS` quietly drifting if the table grew but
+// the union didn't.
+export type CanvasResolution = keyof typeof CANVAS_DIMENSIONS;
+
+// `Object.keys` ordering matches insertion order in `CANVAS_DIMENSIONS` on
+// every supported JS engine; tests pin the order in `index.test.ts`. Reorder
+// the table above with care.
 export const VALID_CANVAS_RESOLUTIONS = Object.keys(
   CANVAS_DIMENSIONS,
 ) as readonly CanvasResolution[];
diff --git a/packages/engine/src/services/videoFrameInjector.ts b/packages/engine/src/services/videoFrameInjector.ts
index f2c957b0f..187a08f19 100644
--- a/packages/engine/src/services/videoFrameInjector.ts
+++ b/packages/engine/src/services/videoFrameInjector.ts
@@ -70,8 +70,12 @@ function createFrameSourceCache(
   function evictOldest(): void {
     const oldestKey = cache.keys().next().value;
     if (!oldestKey) return;
-    totalBytes = Math.max(0, totalBytes - (cache.get(oldestKey)?.length ?? 0));
+    // Snapshot the value before deleting so the byte-size derivation can't
+    // accidentally read post-delete (a future reorder would silently lose
+    // accounting and surface as `totalBytes` drifting out of sync).
+    const dropped = cache.get(oldestKey);
     cache.delete(oldestKey);
+    totalBytes = Math.max(0, totalBytes - (dropped?.length ?? 0));
     evictions++;
   }