fix(embeds): resolve TikTok short links via oEmbed + og:url fallback

TikTok 'copy-link' share URLs (vm.tiktok.com, tiktok.com/t/…) carry no video id
and the homeserver's link preview is bot-walled (generic 'TikTok - Make Your
Day', no og:url/og:image), so they fell through to the static fallback card with
no play button.

New TikTokEmbedCard resolves the id client-side via TikTok's CORS-enabled oEmbed
API on click (keeps the facade privacy model), then plays the player/v1 embed
(portrait, autoplay + full controls + our fullscreen button). Canonical
/video/<id> links skip the lookup. Also added a general og:url fallback so other
short/redirect links resolve to their canonical form when the raw URL doesn't.

Web CSP connect-src gains www.tiktok.com for the oEmbed fetch (desktop already
allows https:). Tests 19/19.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/components/url-preview/UrlPreviewCard.tsx

@@ -19,7 +19,16 @@ import { ImageViewer } from '../image-viewer';
 import { onEnterOrSpace } from '../../utils/keyboard';
 import { useSetting } from '../../state/hooks/settings';
 import { settingsAtom } from '../../state/settings';
-import { getTweetId, MediaEmbed, parseMediaEmbed } from '../../utils/videoEmbed';
+import {
+  getTikTokVideoId,
+  getTweetId,
+  isTikTokLink,
+  MediaEmbed,
+  parseMediaEmbed,
+  tiktokIdFromOembed,
+  tiktokOembedUrl,
+  tiktokPlayerEmbedUrl,
+} from '../../utils/videoEmbed';
 
 const linkStyles = { color: color.Success.Main };
 
@@ -1150,6 +1159,136 @@ function MediaEmbedCard({
   );
 }
 
+// TikTok needs its own card: short "copy-link" URLs (vm.tiktok.com, tiktok.com/t/…)
+// don't carry the video id, and the homeserver's link preview is bot-walled. So we
+// resolve the id client-side via TikTok's CORS-enabled oEmbed API (on click, to
+// keep the facade privacy model), then play the player/v1 embed.
+function TikTokEmbedCard({ url, prev }: { url: string; prev: IPreviewUrlResponse }) {
+  const mx = useMatrixClient();
+  const useAuthentication = useMediaAuthentication();
+  const [inlineMediaEmbeds] = useSetting(settingsAtom, 'inlineMediaEmbeds');
+  const [videoId, setVideoId] = useState<string | null>(() => getTikTokVideoId(url));
+  const [playing, setPlaying] = useState(false);
+  const [resolving, setResolving] = useState(false);
+  const [failed, setFailed] = useState(false);
+  const mediaRef = useRef<HTMLDivElement>(null);
+
+  const mxcImage = prev['og:image'] as string | undefined;
+  const rawTitle = prev['og:title'] ?? '';
+  const title = looksLikeBotWall(rawTitle) ? '' : rawTitle;
+  const thumbnailUrl = mxcImage
+    ? mxcUrlToHttp(mx, mxcImage, useAuthentication, 320, 568, 'scale', false)
+    : undefined;
+
+  const start = useCallback(async () => {
+    if (videoId) {
+      setPlaying(true);
+      return;
+    }
+    setResolving(true);
+    setFailed(false);
+    try {
+      const res = await fetch(tiktokOembedUrl(url));
+      const id = tiktokIdFromOembed(await res.json());
+      if (id) {
+        setVideoId(id);
+        setPlaying(true);
+      } else {
+        setFailed(true);
+      }
+    } catch {
+      setFailed(true);
+    } finally {
+      setResolving(false);
+    }
+  }, [url, videoId]);
+
+  const enterFullscreen = () => mediaRef.current?.requestFullscreen?.().catch(() => undefined);
+
+  const facadeInner = (
+    <>
+      {thumbnailUrl ? (
+        <img className={previewCss.MediaThumbnailImg} src={thumbnailUrl} alt={title} loading="lazy" />
+      ) : (
+        <span className={previewCss.EmbedPlaceholder} />
+      )}
+      <span className={previewCss.MediaPlayOverlay}>
+        <span className={previewCss.MediaPlayButton}>
+          {resolving ? <Spinner size="100" /> : <Icon size="400" src={Icons.Play} />}
+        </span>
+      </span>
+    </>
+  );
+
+  return (
+    <Box direction="Column">
+      <div ref={mediaRef} className={previewCss.EmbedMediaPortrait}>
+        {playing && videoId ? (
+          <iframe
+            className={previewCss.EmbedIframe}
+            src={tiktokPlayerEmbedUrl(videoId)}
+            title={title || 'TikTok'}
+            allow="autoplay; encrypted-media; picture-in-picture; fullscreen; clipboard-write"
+            allowFullScreen
+            loading="lazy"
+          />
+        ) : inlineMediaEmbeds ? (
+          <button
+            type="button"
+            className={previewCss.EmbedFacade}
+            onClick={start}
+            disabled={resolving}
+            aria-label={`Play TikTok${title ? `: ${title}` : ''}`}
+          >
+            {facadeInner}
+          </button>
+        ) : (
+          <a
+            href={url}
+            target="_blank"
+            rel="noreferrer"
+            className={previewCss.EmbedFacade}
+            aria-label={`Open on TikTok${title ? `: ${title}` : ''}`}
+          >
+            {facadeInner}
+          </a>
+        )}
+      </div>
+      <UrlPreviewContent>
+        <Box alignItems="Center" gap="200" justifyContent="SpaceBetween">
+          <Text
+            style={linkStyles}
+            truncate
+            as="a"
+            href={url}
+            target="_blank"
+            rel="noreferrer"
+            size="T200"
+            priority="300"
+          >
+            <SiteBadge label="TikTok" colorClass={previewCss.BadgeTikTok} />
+          </Text>
+          {playing && videoId && (
+            <Chip variant="Secondary" radii="Pill" onClick={enterFullscreen} aria-label="Fullscreen">
+              <Text size="T200">⛶ Fullscreen</Text>
+            </Chip>
+          )}
+        </Box>
+        {failed && (
+          <Text size="T200" style={{ color: color.Critical.Main }}>
+            Couldn’t load this TikTok — open it on TikTok.
+          </Text>
+        )}
+        {!(playing && videoId) && title && (
+          <Text truncate priority="400">
+            <b>{title}</b>
+          </Text>
+        )}
+      </UrlPreviewContent>
+    </Box>
+  );
+}
+
 function GitHubCard({ url, prev }: { url: string; prev: IPreviewUrlResponse }) {
   const title = prev['og:title'] ?? '';
   const description = prev['og:description'] ?? '';
@@ -1764,8 +1903,22 @@ export const UrlPreviewCard = as<'div', { url: string; ts: number }>(
     const renderContent = (prev: IPreviewUrlResponse): React.ReactNode => {
       // Embeddable media (YouTube/Vimeo/TikTok/Dailymotion/Streamable/Twitch/
       // Spotify/SoundCloud/Apple Music/Tidal/Instagram/Reddit) → click-to-play tile.
-      if (embed) {
-        return <MediaEmbedCard url={url} prev={prev} embed={embed} />;
+      // Short "copy-link" share URLs (e.g. vm.tiktok.com, tiktok.com/t/…, youtu.be
+      // redirects) don't carry the id, so fall back to the canonical og:url that
+      // the homeserver already resolved when fetching the preview.
+      const ogUrl = prev['og:url'];
+      const resolvedEmbed =
+        embed ??
+        (typeof ogUrl === 'string' && ogUrl !== url
+          ? parseMediaEmbed(ogUrl, window.location.hostname)
+          : null);
+      if (resolvedEmbed) {
+        return <MediaEmbedCard url={url} prev={prev} embed={resolvedEmbed} />;
+      }
+
+      // TikTok video links (incl. short share links) get their own oEmbed-resolving card.
+      if (isTikTokLink(url)) {
+        return <TikTokEmbedCard url={url} prev={prev} />;
       }
 
       const variant = getCardVariant(url);

src/app/utils/videoEmbed.test.ts

@@ -6,6 +6,9 @@ import {
   isYouTubeShorts,
   getVimeoVideoId,
   getTikTokVideoId,
+  isTikTokLink,
+  tiktokIdFromOembed,
+  tiktokPlayerEmbedUrl,
   getDailymotionId,
   getStreamableId,
   getTwitchTarget,
@@ -40,10 +43,26 @@ test('Vimeo', () => {
 
 test('TikTok: canonical /video/<id> only', () => {
   assert.equal(getTikTokVideoId('https://www.tiktok.com/@user/video/7234567890123456789'), '7234567890123456789');
-  assert.equal(getTikTokVideoId('https://vm.tiktok.com/ZMabc/'), null); // short link redirects
+  assert.equal(getTikTokVideoId('https://vm.tiktok.com/ZMabc/'), null); // short link → oEmbed
   assert.equal(getTikTokVideoId('https://www.tiktok.com/@user'), null);
 });
 
+test('isTikTokLink: canonical + short + vm/vt', () => {
+  assert.equal(isTikTokLink('https://www.tiktok.com/@user/video/123'), true);
+  assert.equal(isTikTokLink('https://www.tiktok.com/t/ZTSHuuXWq/'), true);
+  assert.equal(isTikTokLink('https://vm.tiktok.com/ZMabc/'), true);
+  assert.equal(isTikTokLink('https://www.tiktok.com/@user'), false); // profile, not a video
+  assert.equal(isTikTokLink('https://youtube.com/watch?v=x'), false);
+  assert.equal(parseMediaEmbed('https://www.tiktok.com/@u/video/123', 'h'), null); // handled by its own card
+});
+
+test('tiktokIdFromOembed + player url', () => {
+  assert.equal(tiktokIdFromOembed({ embed_product_id: '7659555276823006478' }), '7659555276823006478');
+  assert.equal(tiktokIdFromOembed({ html: '<blockquote data-video-id="123456">' }), '123456');
+  assert.equal(tiktokIdFromOembed({}), null);
+  assert.ok(tiktokPlayerEmbedUrl('999').startsWith('https://www.tiktok.com/player/v1/999?autoplay=1'));
+});
+
 test('Dailymotion + Streamable', () => {
   assert.equal(getDailymotionId('https://www.dailymotion.com/video/x8abcde'), 'x8abcde');
   assert.equal(getDailymotionId('https://dai.ly/x8abcde'), 'x8abcde');
@@ -104,8 +123,6 @@ test('parseMediaEmbed: routes provider + kind, builds embed URLs', () => {
     embedUrl: 'https://www.youtube-nocookie.com/embed/abc?autoplay=1&rel=0',
   });
   assert.equal(parseMediaEmbed('https://www.youtube.com/watch?v=xyz', HOST)?.kind, 'landscape');
-  assert.equal(parseMediaEmbed('https://www.tiktok.com/@u/video/123', HOST)?.provider, 'tiktok');
-  assert.equal(parseMediaEmbed('https://www.tiktok.com/@u/video/123', HOST)?.kind, 'portrait');
   assert.equal(parseMediaEmbed('https://streamable.com/abc', HOST)?.provider, 'streamable');
   const spotify = parseMediaEmbed('https://open.spotify.com/track/abc', HOST);
   assert.equal(spotify?.kind, 'audio');

src/app/utils/videoEmbed.ts

@@ -71,7 +71,7 @@ export function getVimeoVideoId(url: string): string | null {
 
 // --- TikTok ---------------------------------------------------------------
 
-/** Only resolvable for canonical /video/<id> links (short vm.tiktok.com links redirect). */
+/** Canonical /video/<id> links only; short links resolve via oEmbed (below). */
 export function getTikTokVideoId(url: string): string | null {
   try {
     const { hostname, pathname } = new URL(url);
@@ -84,6 +84,42 @@ export function getTikTokVideoId(url: string): string | null {
   }
 }
 
+/** Any embeddable TikTok video link — canonical, short (/t/, /v/), or vm/vt.tiktok.com. */
+export function isTikTokLink(url: string): boolean {
+  try {
+    const { hostname, pathname } = new URL(url);
+    const h = hostname.replace(/^www\./, '');
+    if (h === 'vm.tiktok.com' || h === 'vt.tiktok.com') return true;
+    if (h === 'tiktok.com') return /^\/(t\/|v\/|embed\/|@[^/]+\/video\/)/.test(pathname);
+    return false;
+  } catch {
+    return false;
+  }
+}
+
+export function tiktokOembedUrl(url: string): string {
+  return `https://www.tiktok.com/oembed?url=${encodeURIComponent(url)}`;
+}
+
+/** Extract the numeric video id from a TikTok oEmbed JSON response. */
+export function tiktokIdFromOembed(data: {
+  embed_product_id?: unknown;
+  html?: unknown;
+}): string | null {
+  const pid = String(data.embed_product_id ?? '').match(/\d+/)?.[0];
+  if (pid) return pid;
+  if (typeof data.html === 'string') {
+    return data.html.match(/data-video-id="(\d+)"/)?.[1] ?? data.html.match(/\/video\/(\d+)/)?.[1] ?? null;
+  }
+  return null;
+}
+
+export function tiktokPlayerEmbedUrl(id: string): string {
+  return `https://www.tiktok.com/player/v1/${encodeURIComponent(
+    id,
+  )}?autoplay=1&music_info=1&description=1&controls=1&progress_bar=1&play_button=1&volume_control=1&fullscreen_button=1&rel=0`;
+}
+
 // --- Dailymotion ----------------------------------------------------------
 
 export function getDailymotionId(url: string): string | null {
@@ -289,13 +325,9 @@ export function parseMediaEmbed(url: string, host: string): MediaEmbed | null {
   if (vimeoId)
     return { provider: 'vimeo', kind: 'landscape', embedUrl: buildVideoEmbedUrl('vimeo', vimeoId) };
 
-  const tiktokId = getTikTokVideoId(url);
-  if (tiktokId)
-    return {
-      provider: 'tiktok',
-      kind: 'portrait',
-      embedUrl: `https://www.tiktok.com/player/v1/${enc(tiktokId)}?music_info=1&description=1&rel=0`,
-    };
+  // NOTE: TikTok is handled by its own card (TikTokEmbedCard) — short "copy-link"
+  // URLs (vm.tiktok.com, tiktok.com/t/…) need a client-side oEmbed lookup to
+  // resolve the video id, which a sync parser can't do. See isTikTokLink below.
 
   const dmId = getDailymotionId(url);
   if (dmId)