diff --git a/apps/web/src/components/chat/MessagesTimeline.test.tsx b/apps/web/src/components/chat/MessagesTimeline.test.tsx
index 8f982064869b..0987b852e716 100644
--- a/apps/web/src/components/chat/MessagesTimeline.test.tsx
+++ b/apps/web/src/components/chat/MessagesTimeline.test.tsx
@@ -791,7 +791,6 @@ describe("MessagesTimeline", () => {
 
     expect(markup).toContain("<video");
     expect(markup).toContain('aria-label="demo.mp4"');
-    expect(markup).toContain('controls=""');
     expect(markup).not.toContain("Expand demo.mp4");
   });
 
diff --git a/apps/web/src/components/chat/MessagesTimeline.tsx b/apps/web/src/components/chat/MessagesTimeline.tsx
index 272ad320ad2b..bc3a66f4e28c 100644
--- a/apps/web/src/components/chat/MessagesTimeline.tsx
+++ b/apps/web/src/components/chat/MessagesTimeline.tsx
@@ -1522,6 +1522,10 @@ function UserVideoAttachment({ file }: { readonly file: ChatFileAttachment }) {
       }
       label={file.name}
       preload="visible"
+      onOpen={() => {
+        const preview = buildAttachmentVideoPreview(ctx.activeThreadEnvironmentId, file);
+        if (preview) ctx.onImageExpand(preview);
+      }}
       className="block aspect-[4/3] w-full"
       videoClassName="aspect-auto size-full rounded-lg border border-border/80"
       stateClassName="aspect-auto min-h-full rounded-lg border border-border/80 bg-black text-white"
diff --git a/apps/web/src/components/media/MediaVideoPlayer.tsx b/apps/web/src/components/media/MediaVideoPlayer.tsx
index 6f2b15e7a73e..9bf65102bf70 100644
--- a/apps/web/src/components/media/MediaVideoPlayer.tsx
+++ b/apps/web/src/components/media/MediaVideoPlayer.tsx
@@ -1,4 +1,4 @@
-import { RotateCwIcon, TriangleAlertIcon } from "lucide-react";
+import { PlayIcon, RotateCwIcon, TriangleAlertIcon } from "lucide-react";
 import { useCallback, useEffect, useRef, useState, type CSSProperties } from "react";
 
 import { cn } from "../../lib/utils";
@@ -15,6 +15,8 @@ interface MediaVideoPlayerProps {
   readonly revision?: string | null | undefined;
   readonly preload?: "visible" | "metadata" | undefined;
   readonly autoPlay?: boolean | undefined;
+  /** Presents a still thumbnail whose full surface opens the video in a viewer. */
+  readonly onOpen?: (() => void) | undefined;
   readonly className?: string | undefined;
   readonly videoClassName?: string | undefined;
   /** Styles the loading and failure panels, which otherwise assume an inline light surface. */
@@ -34,6 +36,7 @@ export function MediaVideoPlayer({
   revision = null,
   preload = "visible",
   autoPlay = false,
+  onOpen,
   className,
   videoClassName,
   stateClassName,
@@ -131,7 +134,7 @@ export function MediaVideoPlayer({
       style={style}
       data-markdown-copy={copyMarkdown}
     >
-      {failed ? (
+      {failed && !onOpen ? (
         <span
           role="alert"
           className={cn(
@@ -160,17 +163,23 @@ export function MediaVideoPlayer({
             <OpenMediaLink originalUrl={originalUrl} src={latestSrc ?? src} fileName={label} />
           </span>
         </span>
-      ) : src !== null ? (
+      ) : src !== null && !failed ? (
         <video
           key={loadAttempt}
           ref={videoRef}
           src={src}
           aria-label={label || "Video preview"}
-          autoPlay={autoPlay}
-          controls
+          aria-hidden={onOpen ? true : undefined}
+          autoPlay={onOpen ? false : autoPlay}
+          controls={!onOpen}
+          muted={onOpen ? true : undefined}
           playsInline
           preload={preload === "metadata" || preloadedSrc === src ? "metadata" : "none"}
-          className={cn("aspect-video max-h-full w-full bg-black object-contain", videoClassName)}
+          className={cn(
+            "aspect-video max-h-full w-full bg-black object-contain",
+            onOpen && "pointer-events-none",
+            videoClassName,
+          )}
           style={style}
           onLoadedMetadata={(event) => prepareVideoFirstFrame(event.currentTarget)}
           onPlay={() => setPlaybackSource({ src, revision: sourceRevision })}
@@ -184,11 +193,23 @@ export function MediaVideoPlayer({
       ) : (
         <span
           role="status"
-          aria-label="Loading video"
+          aria-label={failed ? "Video preview unavailable" : "Loading video"}
           className={cn("block aspect-video w-full rounded-lg bg-muted/60", stateClassName)}
           style={style}
         />
       )}
+      {onOpen ? (
+        <button
+          type="button"
+          aria-label={label ? `Play ${label}` : "Play video"}
+          onClick={onOpen}
+          className="absolute inset-0 flex cursor-pointer items-center justify-center rounded-lg focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-ring"
+        >
+          <span className="flex size-8 items-center justify-center rounded-full bg-black/50 text-white">
+            <PlayIcon aria-hidden className="size-4 fill-current" />
+          </span>
+        </button>
+      ) : null}
     </span>
   );
   return actionsSource ? <MediaActions source={actionsSource}>{player}</MediaActions> : player;