diff --git a/frontend/libs/components/video-editor/src/lib/media/thumbnail.spec.ts b/frontend/libs/components/video-editor/src/lib/media/thumbnail.spec.ts
new file mode 100644
--- /dev/null
+++ b/frontend/libs/components/video-editor/src/lib/media/thumbnail.spec.ts
@@ -0,0 +1,31 @@
+import { expect, it } from "vitest";
+import { thumbnailSize } from "./thumbnail";
+
+it.each([
+  [8192, 1, 1280, 1],
+  [1, 8192, 1, 720],
+  [96, 48, 96, 48],
+  [4096, 2048, 1280, 640],
+  [2048, 4096, 360, 720],
+  [1280, 720, 1280, 720],
+])("sizes a %dx%d image to a nonempty %dx%d thumbnail", (width, height, expectedWidth, expectedHeight) => {
+  expect(thumbnailSize({ width, height })).toEqual({
+    width: expectedWidth,
+    height: expectedHeight,
+  });
+});
+
+it.each([
+  [0, 8192, 0, 720],
+  [8192, 0, 1280, 0],
+  [Infinity, 1, 1280, 0],
+  [1, Infinity, 0, 720],
+  [NaN, 8192, NaN, 720],
+  [-1, 8192, -0, 720],
+  [8192, -1, 1280, -0],
+])("preserves sizing behavior for invalid %dx%d dimensions", (width, height, expectedWidth, expectedHeight) => {
+  expect(thumbnailSize({ width, height })).toEqual({
+    width: expectedWidth,
+    height: expectedHeight,
+  });
+});
diff --git a/frontend/libs/components/video-editor/src/lib/media/thumbnail.ts b/frontend/libs/components/video-editor/src/lib/media/thumbnail.ts
--- a/frontend/libs/components/video-editor/src/lib/media/thumbnail.ts
+++ b/frontend/libs/components/video-editor/src/lib/media/thumbnail.ts
@@ -21,6 +21,11 @@ export function thumbnailSize({
     targetWidth = Math.round(targetHeight * aspectRatio);
   }
 
+  if (width > 0 && height > 0 && Number.isFinite(width) && Number.isFinite(height)) {
+    targetWidth = Math.max(1, targetWidth);
+    targetHeight = Math.max(1, targetHeight);
+  }
+
   return { width: targetWidth, height: targetHeight };
 }