fix(webui): persist markdown video previews

webui/src/components/MarkdownTextRenderer.tsx

@@ -8,6 +8,7 @@ import remarkMath from "remark-math";
 
 import { CodeBlock } from "@/components/CodeBlock";
 import { FileReferenceChip, isLikelyFilePath } from "@/components/FileReferenceChip";
+import { inferMediaKind } from "@/lib/media";
 import { cn } from "@/lib/utils";
 
 import "katex/dist/katex.min.css";
@@ -114,6 +115,29 @@ export default function MarkdownTextRenderer({
         const source = typeof src === "string" ? src : "";
         if (!source) return null;
         const label = typeof alt === "string" ? alt : "";
+        if (inferMediaKind({ url: source, name: label }) === "video") {
+          return (
+            <span
+              className={cn(
+                "not-prose my-3 block w-fit max-w-full overflow-hidden rounded-[14px]",
+                "border border-border/70 bg-background shadow-sm",
+              )}
+            >
+              <video
+                src={source}
+                controls
+                preload="metadata"
+                className="block max-h-[26rem] max-w-full bg-black"
+                aria-label={label ? `Video attachment: ${label}` : "Video attachment"}
+              />
+              {label ? (
+                <span className="block max-w-full truncate px-3 py-2 text-xs text-muted-foreground">
+                  {label}
+                </span>
+              ) : null}
+            </span>
+          );
+        }
         return (
           <span
             className={cn(

webui/src/tests/markdown-text-renderer.test.tsx

@@ -15,4 +15,14 @@ describe("MarkdownTextRenderer", () => {
     );
     expect(screen.getByText("Diagram")).toBeInTheDocument();
   });
+
+  it("renders markdown videos as inline players", () => {
+    render(<MarkdownTextRenderer>![nanobot-intro.mp4](/api/media/sig/video)</MarkdownTextRenderer>);
+
+    const video = screen.getByLabelText("Video attachment: nanobot-intro.mp4");
+    expect(video.tagName).toBe("VIDEO");
+    expect(video).toHaveAttribute("src", "/api/media/sig/video");
+    expect(video).toHaveAttribute("controls");
+    expect(screen.queryByRole("img", { name: "nanobot-intro.mp4" })).not.toBeInTheDocument();
+  });
 });