PAP-10499: guard video thumbnail fallback

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/components/artifacts/ArtifactCard.test.tsx

@@ -130,6 +130,44 @@ describe("ArtifactCard", () => {
     container.remove();
   });
 
+  it("reveals video previews if the browser does not report seek completion", () => {
+    vi.useFakeTimers();
+    const container = document.createElement("div");
+    document.body.appendChild(container);
+    const root = createRoot(container);
+
+    try {
+      flushSync(() => {
+        root.render(
+          <ArtifactCard
+            artifact={makeArtifact({ mediaKind: "video", contentType: "video/mp4", contentPath: "/files/clip.mp4" })}
+          />,
+        );
+      });
+
+      const video = container.querySelector("video") as HTMLVideoElement;
+      expect(video).not.toBeNull();
+      expect(video.dataset.frameReady).toBe("false");
+
+      flushSync(() => {
+        video.dispatchEvent(new Event("loadedmetadata", { bubbles: true }));
+      });
+
+      expect(video.currentTime).toBe(0.05);
+      expect(video.dataset.frameReady).toBe("false");
+
+      flushSync(() => {
+        vi.advanceTimersByTime(3000);
+      });
+
+      expect(video.dataset.frameReady).toBe("true");
+    } finally {
+      flushSync(() => root.unmount());
+      container.remove();
+      vi.useRealTimers();
+    }
+  });
+
   it("renders a falling-back video placeholder when no content path exists", () => {
     const markup = renderToStaticMarkup(
       <ArtifactCard artifact={makeArtifact({ mediaKind: "video", contentPath: null })} />,

ui/src/components/artifacts/ArtifactCard.tsx

@@ -1,4 +1,4 @@
-import { type SyntheticEvent, useRef, useState } from "react";
+import { type SyntheticEvent, useEffect, useRef, useState } from "react";
 import { Download, ExternalLink, Paperclip, Play } from "lucide-react";
 import type { CompanyArtifact } from "@/api/artifacts";
 import { Link } from "@/lib/router";
@@ -54,6 +54,14 @@ function VideoPreview({ artifact }: { artifact: CompanyArtifact }) {
   const [errored, setErrored] = useState(false);
   const [frameReady, setFrameReady] = useState(false);
   const thumbnailSeekRequested = useRef(false);
+  const frameReadyFallbackTimer = useRef<number | null>(null);
+  useEffect(() => {
+    return () => {
+      if (frameReadyFallbackTimer.current !== null) {
+        window.clearTimeout(frameReadyFallbackTimer.current);
+      }
+    };
+  }, []);
   if (errored || !artifact.contentPath) {
     return (
       <PreviewFrame className="flex items-center justify-center bg-black/80">
@@ -64,7 +72,19 @@ function VideoPreview({ artifact }: { artifact: CompanyArtifact }) {
     );
   }
 
-  const markFrameReady = () => setFrameReady(true);
+  const markFrameReady = () => {
+    if (frameReadyFallbackTimer.current !== null) {
+      window.clearTimeout(frameReadyFallbackTimer.current);
+      frameReadyFallbackTimer.current = null;
+    }
+    setFrameReady(true);
+  };
+  const scheduleFrameReadyFallback = () => {
+    if (frameReadyFallbackTimer.current !== null) {
+      window.clearTimeout(frameReadyFallbackTimer.current);
+    }
+    frameReadyFallbackTimer.current = window.setTimeout(markFrameReady, 3000);
+  };
   const loadThumbnailFrame = (event: SyntheticEvent<HTMLVideoElement>) => {
     if (thumbnailSeekRequested.current) return;
     thumbnailSeekRequested.current = true;
@@ -74,6 +94,9 @@ function VideoPreview({ artifact }: { artifact: CompanyArtifact }) {
     try {
       if (Math.abs(video.currentTime - seekTarget) > 0.001) {
         video.currentTime = seekTarget;
+        scheduleFrameReadyFallback();
+      } else {
+        markFrameReady();
       }
     } catch {
       markFrameReady();