feat(feed): hover infobox on feed cards — full title, description, tags (E8·S3)

frontend/src/components/VideoCard.tsx

@@ -17,6 +17,7 @@ import {
 import Avatar from "./Avatar";
 import AddToPlaylist from "./AddToPlaylist";
 import DownloadButton from "./DownloadButton";
+import VideoInfoCard from "./VideoInfoCard";
 import clsx from "clsx";
 import type { Video, VideoStatus } from "../lib/api";
 import { FEED_VIEW_SPEC, type FeedView } from "../lib/feedView";
@@ -105,6 +106,17 @@ function Actions({
   );
 }
 
+// The hover-infobox trigger skins (E8·S3). The ⓘ is hover-revealed and dropped on touch (`reveal-hover`
+// + the group opacity toggle), and lives OUTSIDE the six-button action budget — as a thumbnail-corner
+// overlay for the thumbnailed views, and inline beside the actions for the one-line row.
+const INFO_REVEAL =
+  "reveal-hover opacity-0 group-hover:opacity-100 group-focus-within:opacity-100 focus-visible:opacity-100 transition-opacity";
+const INFO_OVERLAY = clsx(
+  INFO_REVEAL,
+  "absolute bottom-1.5 left-1.5 z-10 rounded-md bg-black/70 p-1 text-white hover:bg-black/85",
+);
+const INFO_INLINE = clsx(INFO_REVEAL, "rounded-md p-1.5 text-muted hover:bg-surface hover:text-fg");
+
 // Plain left-click opens the in-app player (the experiment); Ctrl/Cmd/middle-click
 // keep the native "open youtube.com in a new tab" behavior via the underlying href.
 function openInApp(
@@ -312,6 +324,10 @@ function Thumb({
           )}
         </div>
       )}
+      {/* Hover infobox trigger (E8·S3), docked bottom-left so it clears the centered play overlay, the
+          corner badges (saved / stream, top corners) and the duration (bottom-right). Revealed with the
+          rest of the hover chrome, dropped on touch. */}
+      <VideoInfoCard video={video} className={INFO_OVERLAY} />
       {/* Resume progress bar (sits at the very bottom, under the duration badge). */}
       {pct > 0 && (
         <div className="absolute bottom-0 left-0 right-0 h-1 bg-black/40">
@@ -330,7 +346,7 @@ function Thumb({
 // Keep this table and the classes in step; each number is measured against the worst case in the
 // LIBRARY and in BOTH languages — see the row's own comment for where each comes from.
 const ROW_COL = {
-  actions: 192, // w-48 — six buttons at 28 + five 4px gaps = 188
+  actions: 224, // w-48 (six buttons: 6×28 + 5×4 = 188) + gap-1 + the 28px inline info trigger
   channel: 128, // w-32
   meta: 104, //   RowMetaCells' own grid: 4rem + 1rem + 1rem + two 4px gaps
   views: 64, //   w-16
@@ -508,8 +524,13 @@ function VideoCard({
           className={clsx(rowShell, "flex items-center gap-3 px-3 py-2", watched && "opacity-55")}
         >
           {/* Actions lead: this is where the eye already is (the title is the thing you read), so
-              they're the shortest pointer trip from it. */}
-          <div className="shrink-0 w-48">{actions}</div>
+              they're the shortest pointer trip from it. This row has no thumbnail to host the info
+              trigger, so it sits inline right after the actions (still outside their six-button
+              budget). ROW_COL.actions already counts its width. */}
+          <div className="shrink-0 flex items-center gap-1">
+            <div className="w-48">{actions}</div>
+            <VideoInfoCard video={video} className={INFO_INLINE} />
+          </div>
           {/* Everything else is shrink-0, so the title is the only thing that can give — which means
               once the fixed columns outgrow the row, it gives ALL of it and vanishes. Columns drop
               from the right as the row narrows, least important first: a title with no date beats a

frontend/src/components/VideoInfoCard.dom.test.tsx

@@ -0,0 +1,130 @@
+// @vitest-environment jsdom
+//
+// Contract of the feed-card hover infobox (E8·S3): the trigger stays closed until opened; on open the
+// header (full title + channel) renders IMMEDIATELY from the Video we already hold, while the
+// description (videoDetail) and the channel's tags (channelDetail.tag_ids resolved against the tag
+// list) fill in from their on-demand queries; an empty description falls back to the "no description"
+// line. i18n is key-passthrough and the AnchoredPopover platform is floating-ui (hover mode → open via
+// focus), so we stub the observers autoUpdate wires and wrap in a FloatingTree + QueryClient.
+import { describe, it, expect, afterEach, beforeAll, vi } from "vitest";
+import { render, screen, fireEvent, cleanup } from "@testing-library/react";
+import { FloatingTree } from "@floating-ui/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+vi.mock("react-i18next", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("react-i18next")>();
+  return {
+    ...actual,
+    useTranslation: () => ({ t: (key: string) => key, i18n: { language: "en" } }),
+  };
+});
+
+const videoDetail = vi.fn();
+const channelDetail = vi.fn();
+const tags = vi.fn();
+vi.mock("../lib/api", () => ({
+  api: {
+    videoDetail: (...a: unknown[]) => videoDetail(...a),
+    channelDetail: (...a: unknown[]) => channelDetail(...a),
+    tags: (...a: unknown[]) => tags(...a),
+  },
+}));
+
+import VideoInfoCard from "./VideoInfoCard";
+import type { Video } from "../lib/api";
+
+beforeAll(() => {
+  class Stub {
+    observe() {}
+    unobserve() {}
+    disconnect() {}
+    takeRecords() {
+      return [];
+    }
+  }
+  globalThis.ResizeObserver ??= Stub as unknown as typeof ResizeObserver;
+  globalThis.IntersectionObserver ??= Stub as unknown as typeof IntersectionObserver;
+});
+
+afterEach(() => {
+  cleanup();
+  vi.clearAllMocks();
+});
+
+const video = (over: Partial<Video> = {}): Video =>
+  ({
+    id: "v1",
+    title: "The full untruncated title",
+    channel_id: "c1",
+    channel_title: "Test Channel",
+    channel_thumbnail: null,
+    channel_url: "https://youtube.com/c1",
+    published_at: "2026-02-24T00:00:00Z",
+    thumbnail_url: null,
+    duration_seconds: 754,
+    view_count: 1512,
+    is_short: false,
+    live_status: "none",
+    status: "new",
+    position_seconds: 0,
+    saved: false,
+    watch_url: "https://youtu.be/v1",
+    ...over,
+  }) as Video;
+
+const open = (v: Video = video()) => {
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  render(
+    <QueryClientProvider client={qc}>
+      <FloatingTree>
+        <VideoInfoCard video={v} className="info-trigger" />
+      </FloatingTree>
+    </QueryClientProvider>,
+  );
+  fireEvent.focus(screen.getByRole("button", { name: "card.info" }));
+};
+
+describe("VideoInfoCard", () => {
+  it("renders a trigger, panel closed until opened (no fetch at rest)", () => {
+    const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+    render(
+      <QueryClientProvider client={qc}>
+        <FloatingTree>
+          <VideoInfoCard video={video()} className="info-trigger" />
+        </FloatingTree>
+      </QueryClientProvider>,
+    );
+    expect(screen.getByRole("button", { name: "card.info" })).toBeTruthy();
+    expect(screen.queryByText("The full untruncated title")).toBeNull();
+    // `enabled: open` gates the queries — nothing fired while closed.
+    expect(videoDetail).not.toHaveBeenCalled();
+    expect(channelDetail).not.toHaveBeenCalled();
+  });
+
+  it("shows the header immediately from the Video, then fills in description + tags on load", async () => {
+    videoDetail.mockResolvedValue({ id: "v1", description: "A longer description snippet." });
+    channelDetail.mockResolvedValue({ id: "c1", tag_ids: [1, 3] });
+    tags.mockResolvedValue([
+      { id: 1, name: "English", category: "language" },
+      { id: 2, name: "Unused", category: "topic" },
+      { id: 3, name: "Astronomy", category: "topic" },
+    ]);
+    open();
+    // Header is from the Video prop — present without waiting on any query.
+    expect(screen.getByText("The full untruncated title")).toBeTruthy();
+    expect(screen.getByText("Test Channel")).toBeTruthy();
+    // Description + only the channel's own tags (1 + 3, not 2) once the queries resolve.
+    expect(await screen.findByText("A longer description snippet.")).toBeTruthy();
+    expect(await screen.findByText("English")).toBeTruthy();
+    expect(await screen.findByText("Astronomy")).toBeTruthy();
+    expect(screen.queryByText("Unused")).toBeNull();
+  });
+
+  it("falls back to the no-description line when the video has none", async () => {
+    videoDetail.mockResolvedValue({ id: "v1", description: null });
+    channelDetail.mockResolvedValue({ id: "c1", tag_ids: [] });
+    tags.mockResolvedValue([]);
+    open();
+    expect(await screen.findByText("card.noDescription")).toBeTruthy();
+  });
+});

frontend/src/components/VideoInfoCard.tsx

@@ -0,0 +1,143 @@
+import { useState } from "react";
+import { useTranslation } from "react-i18next";
+import { useQuery } from "@tanstack/react-query";
+import { Info } from "lucide-react";
+import { qk } from "../lib/queryKeys";
+import { api, type Video } from "../lib/api";
+import { formatDate, formatDuration, formatViews } from "../lib/format";
+import { linkify } from "../lib/linkify";
+import Avatar from "./Avatar";
+import { PopoverSurface, useAnchoredPopover } from "./AnchoredPopover";
+
+// The feed card's "more than the card face" hover infobox (E8·S3, decision D3): full (un-clamped)
+// title, channel, views·duration·date, a description snippet, and the channel's tags. It hangs off a
+// small ⓘ button — a thumbnail-corner overlay in the four thumbnailed views, an inline button beside
+// the actions in the one-line row (see the caller). It reveals only with the other hover controls on a
+// mouse and is dropped entirely on touch (`.reveal-hover`), where a tap already plays/resumes and a
+// hover card would only be an invisible trap. Hover mode also opens it on keyboard focus, so it stays
+// reachable by Tab.
+//
+// The card face already carries title/channel/date/duration/views, so the box's real added value is
+// the FULL title (the card clamps to 2 lines) plus the description + tags, which aren't in the feed
+// list payload. Both are fetched ON DEMAND on open (like AboutCell): the description via
+// `videoDetail`, the tags by resolving the channel's `tag_ids` (from `channelDetail`, shared with the
+// channel page's cache) against the tag list. Until they land the header still shows from the Video
+// we already have, so the box is never empty.
+//
+// The caller owns the trigger's placement + reveal via `className`: a thumbnail-corner overlay for the
+// four thumbnailed views, an inline button beside the actions for the one-line row. The action ROW
+// itself is budgeted to exactly six buttons (a seventh wraps in every view — see VideoCard's ROW_COL),
+// so the trigger deliberately lives OUTSIDE it.
+export default function VideoInfoCard({
+  video,
+  className,
+}: {
+  video: Video;
+  /** Trigger-button classes (placement + hover-reveal + skin). The reveal/touch-suppression rules
+   *  live here so each host can match its surface (overlay vs inline). */
+  className?: string;
+}) {
+  const { t, i18n } = useTranslation();
+  const [open, setOpen] = useState(false);
+
+  const pop = useAnchoredPopover({
+    open,
+    onOpenChange: setOpen,
+    mode: "hover",
+    placement: "bottom-end",
+    offset: 6,
+    // A touch of open intent (so brushing past the button while reaching another control doesn't
+    // pop it), a longer close grace so the cursor can travel into the interactive card.
+    hoverDelay: { open: 140, close: 160 },
+    fitHeight: true,
+  });
+
+  const { data: detail } = useQuery({
+    queryKey: qk.videoDetail(video.id),
+    queryFn: () => api.videoDetail(video.id),
+    enabled: open,
+    staleTime: 5 * 60_000,
+  });
+  const { data: channel } = useQuery({
+    queryKey: qk.channel(video.channel_id),
+    queryFn: () => api.channelDetail(video.channel_id),
+    enabled: open && !!video.channel_id,
+    staleTime: 5 * 60_000,
+  });
+  const { data: tags } = useQuery({
+    queryKey: qk.tags(),
+    queryFn: () => api.tags(),
+    enabled: open,
+    staleTime: 5 * 60_000,
+  });
+
+  // The channel's tags (`tag_ids`), in the channel's own id order, resolved to names via the tag list.
+  // These are the channel-tags the channel actually carries; an unknown id (a just-deleted tag) drops.
+  const tagNames =
+    channel && tags
+      ? channel.tag_ids
+          .map((id) => tags.find((tg) => tg.id === id))
+          .filter((tg): tg is NonNullable<typeof tg> => !!tg)
+      : [];
+
+  const description = detail?.description?.trim();
+  const metaBits = [
+    video.view_count != null ? `${formatViews(video.view_count)} ${t("card.views")}` : null,
+    video.duration_seconds != null ? formatDuration(video.duration_seconds) : null,
+    video.published_at ? formatDate(video.published_at, i18n.language) : null,
+  ].filter(Boolean);
+
+  return (
+    <>
+      <button
+        type="button"
+        ref={pop.refs.setReference}
+        {...pop.getReferenceProps()}
+        // The overlay trigger sits inside the thumbnail's <a> (like the play buttons), so a click must
+        // both preventDefault (no navigation) and stopPropagation (no card open); harmless inline too.
+        onClick={(e) => {
+          e.preventDefault();
+          e.stopPropagation();
+        }}
+        aria-label={t("card.info")}
+        title={t("card.info")}
+        className={className}
+      >
+        <Info className="w-4 h-4" />
+      </button>
+      <PopoverSurface
+        popover={pop}
+        ariaLabel={t("card.info")}
+        className="glass w-[340px] max-w-[92vw] overflow-y-auto rounded-lg px-3.5 py-3 animate-[fadeIn_0.12s_ease]"
+        style={{ maxHeight: "min(26rem, var(--fit-max-h, 26rem))" }}
+      >
+        <p className="text-sm font-medium leading-snug wrap-break-word">{video.title}</p>
+        <div className="mt-2 flex items-center gap-2">
+          <Avatar
+            src={video.channel_thumbnail}
+            fallback={video.channel_title ?? ""}
+            className="w-6 h-6 rounded-full shrink-0"
+          />
+          <span className="text-xs text-muted truncate">{video.channel_title}</span>
+        </div>
+        {metaBits.length > 0 && <p className="mt-1.5 text-xs text-muted">{metaBits.join(" · ")}</p>}
+        {description ? (
+          <p className="mt-2.5 text-xs leading-relaxed text-muted line-clamp-5 wrap-break-word">
+            {linkify(description)}
+          </p>
+        ) : detail ? (
+          <p className="mt-2.5 text-xs italic text-muted">{t("card.noDescription")}</p>
+        ) : null}
+        {tagNames.length > 0 && (
+          <div className="mt-3 flex flex-wrap gap-1.5">
+            {tagNames.map((tg) => (
+              <span key={tg.id} className="glass-card px-2 py-0.5 rounded-full text-2xs">
+                {tg.name}
+              </span>
+            ))}
+          </div>
+        )}
+      </PopoverSurface>
+    </>
+  );
+}

frontend/src/i18n/locales/en/card.json

@@ -17,5 +17,7 @@
   "restart": "Restart",
   "play": "Play",
   "stream": "stream",
-  "views": "views"
+  "views": "views",
+  "info": "Details",
+  "noDescription": "No description"
 }

frontend/src/i18n/locales/hu/card.json

@@ -17,5 +17,7 @@
   "restart": "Elölről",
   "play": "Lejátszás",
   "stream": "stream",
-  "views": "megtekintés"
+  "views": "megtekintés",
+  "info": "Részletek",
+  "noDescription": "Nincs leírás"
 }