feat(channel): enrich the About tab + fix the tab-switch header shift

- fix: reserve the scrollbar gutter (scrollbar-gutter:stable) on the channel
  page's scroll container, so switching between the tall Videos tab and the
  short About tab no longer shifts the banner/avatar/buttons a few px sideways
  (the vertical scrollbar was appearing/disappearing between the two tabs).
- About tab now shows Country (flag + localized name), Language, Topics
  (topicCategories → readable chips), and Keywords (brandingSettings keywords
  parsed into chips, quoted multi-word tags kept whole). country/language/topics
  were already stored; keywords is new (migration 0055_channel_keywords, mapped
  in apply_channel_details, returned by channel_detail).
- Discovery → channel page: the Channel-manager "Discover from playlists" tab now
  links each channel name to its in-app channel page (ChannelLink onView), so a
  discovered channel's About/videos can be inspected BEFORE subscribing (was
  subscribe-only, plain text before).

Note: the channel info-card epic itself was already delivered in v0.19.0; this is
the About-tab enrichment follow-up + the header-shift fix. external_links stays
empty by design (YouTube removed the field from the Data API ~2023).

backend/alembic/versions/0055_channel_keywords.py

@@ -0,0 +1,23 @@
+"""channels.keywords: creator keyword tags from brandingSettings (About tab)
+
+Revision ID: 0055_channel_keywords
+Revises: 0054_audit_log
+Create Date: 2026-07-12
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = "0055_channel_keywords"
+down_revision: Union[str, None] = "0054_audit_log"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column("channels", sa.Column("keywords", sa.Text(), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column("channels", "keywords")

backend/app/models.py

@@ -180,6 +180,9 @@ class Channel(Base, TimestampMixin):
     topic_categories: Mapped[list | None] = mapped_column(JSON)
     default_language: Mapped[str | None] = mapped_column(String(16))
     country: Mapped[str | None] = mapped_column(String(8))
+    # Creator keyword tags (brandingSettings.channel.keywords) — a single space-separated string,
+    # multi-word tags quoted; the client parses it into chips for the About tab.
+    keywords: Mapped[str | None] = mapped_column(Text)
 
     # Sync bookkeeping.
     details_synced_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))

backend/app/routes/channels.py

@@ -233,6 +233,9 @@ def _channel_detail_dict(
         "published_at": channel.published_at.isoformat() if channel.published_at else None,
         "external_links": channel.external_links or [],
         "country": channel.country,
+        "default_language": channel.default_language,
+        "topic_categories": channel.topic_categories or [],
+        "keywords": channel.keywords,
         "subscribed": subscribed,
         "explored": explored,
         "blocked": blocked,

backend/app/sync/subscriptions.py

@@ -69,6 +69,7 @@ def apply_channel_details(db: Session, items: list[dict]) -> None:
         channel.banner_url = branding.get("image", {}).get("bannerExternalUrl")
         channel.external_links = _external_links(branding)
         channel.topic_categories = topics.get("topicCategories")
+        channel.keywords = branding.get("channel", {}).get("keywords")
         channel.details_synced_at = now
 
 

frontend/src/components/ChannelDiscovery.tsx

@@ -18,9 +18,11 @@ import { useConfirm } from "./ConfirmProvider";
 export default function ChannelDiscovery({
   canWrite,
   onOpenWizard,
+  onViewChannel,
 }: {
   canWrite: boolean;
   onOpenWizard: () => void;
+  onViewChannel: (id: string, name: string) => void;
 }) {
   const { t } = useTranslation();
   const qc = useQueryClient();
@@ -76,7 +78,13 @@ export default function ChannelDiscovery({
       filter: { kind: "text", get: (c) => `${c.title ?? ""} ${c.handle ?? ""}` },
       cardPrimary: true,
       render: (c) => (
-        <ChannelLink id={c.id} title={c.title} handle={c.handle} thumbnailUrl={c.thumbnail_url} />
+        <ChannelLink
+          id={c.id}
+          title={c.title}
+          handle={c.handle}
+          thumbnailUrl={c.thumbnail_url}
+          onView={() => onViewChannel(c.id, c.title ?? c.id)}
+        />
       ),
     },
     subsColumn<DiscoveredChannel>(t),

frontend/src/components/ChannelPage.tsx

@@ -10,6 +10,39 @@ import { notifyYouTubeActionError } from "../lib/youtubeErrors";
 import { api, type FeedFilters, type Me } from "../lib/api";
 import { channelYouTubeUrl, formatViews } from "../lib/format";
 
+// --- About-tab metadata helpers ---
+// ISO 3166-1 alpha-2 code → 🇺🇸 regional-indicator flag emoji.
+function countryFlag(code: string): string {
+  if (!/^[A-Za-z]{2}$/.test(code)) return "";
+  return String.fromCodePoint(...[...code.toUpperCase()].map((c) => 0x1f1e6 + c.charCodeAt(0) - 65));
+}
+function displayName(code: string, lang: string, type: "region" | "language"): string {
+  try {
+    return new Intl.DisplayNames([lang], { type }).of(type === "region" ? code.toUpperCase() : code) ?? code;
+  } catch {
+    return code;
+  }
+}
+// YouTube keywords are ONE space-separated string with multi-word tags quoted: gaming "let's play".
+function parseKeywords(s: string): string[] {
+  return (s.match(/"[^"]+"|\S+/g) ?? []).map((k) => k.replace(/^"|"$/g, "")).filter(Boolean);
+}
+// topicCategories are Wikipedia URLs (…/wiki/Music) → a readable label, de-duplicated.
+function topicLabels(urls: string[]): string[] {
+  const seen = new Set<string>();
+  for (const url of urls) {
+    const seg = url.split("/wiki/")[1] ?? url.split("/").pop() ?? url;
+    let label = seg;
+    try {
+      label = decodeURIComponent(seg);
+    } catch {
+      /* keep raw */
+    }
+    seen.add(label.replace(/_/g, " "));
+  }
+  return [...seen];
+}
+
 // A dedicated channel page: an "About"-style header (banner, avatar, stats, subscribe) over the
 // channel's videos (the catalog filtered to this channel). For an un-subscribed channel it
 // auto-ingests recent uploads in the background ("explore") so they're browsable immediately,
@@ -147,13 +180,20 @@ export default function ChannelPage({
     ch?.total_view_count != null ? t("channel.totalViews", { formatted: formatViews(ch.total_view_count) }) : null,
     joined ? t("channel.joined", { date: joined }) : null,
   ].filter(Boolean) as string[];
+  const topics = ch?.topic_categories?.length ? topicLabels(ch.topic_categories) : [];
+  const keywords = ch?.keywords ? parseKeywords(ch.keywords) : [];
+  const hasAboutDetails =
+    !!ch?.country || !!ch?.default_language || topics.length > 0 || keywords.length > 0;
   const tabClass = (active: boolean) =>
     active
       ? "pb-2 text-sm font-medium border-b-2 border-fg text-fg"
       : "pb-2 text-sm text-muted hover:text-fg border-b-2 border-transparent";
 
   return (
-    <main className="flex-1 min-w-0 overflow-y-auto">
+    // scrollbar-gutter:stable reserves the scrollbar track on BOTH tabs, so switching between the
+    // tall Videos tab (scrollbar) and the short About tab (no scrollbar) no longer shifts the
+    // header/logo/buttons horizontally as the scrollbar appears/disappears.
+    <main className="flex-1 min-w-0 overflow-y-auto [scrollbar-gutter:stable]">
       {/* Banner + back — OPTION C: inset, rounded card (not full-bleed) */}
       <div className="relative px-4 sm:px-6 pt-3">
         {ch?.banner_url ? (
@@ -341,6 +381,48 @@ export default function ChannelPage({
               ))}
             </div>
           )}
+          {hasAboutDetails && (
+            <div className="mt-5 space-y-2.5 text-sm border-t border-border pt-4">
+              {ch?.country && (
+                <div className="flex gap-2">
+                  <span className="text-muted w-24 shrink-0">{t("channel.country")}</span>
+                  <span>
+                    {countryFlag(ch.country)} {displayName(ch.country, i18n.language, "region")}
+                  </span>
+                </div>
+              )}
+              {ch?.default_language && (
+                <div className="flex gap-2">
+                  <span className="text-muted w-24 shrink-0">{t("channel.language")}</span>
+                  <span>{displayName(ch.default_language, i18n.language, "language")}</span>
+                </div>
+              )}
+              {topics.length > 0 && (
+                <div className="flex gap-2">
+                  <span className="text-muted w-24 shrink-0 pt-0.5">{t("channel.topics")}</span>
+                  <div className="flex flex-wrap gap-1.5">
+                    {topics.map((tp) => (
+                      <span key={tp} className="glass-card px-2 py-0.5 rounded-full text-xs">
+                        {tp}
+                      </span>
+                    ))}
+                  </div>
+                </div>
+              )}
+              {keywords.length > 0 && (
+                <div className="flex gap-2">
+                  <span className="text-muted w-24 shrink-0 pt-0.5">{t("channel.keywords")}</span>
+                  <div className="flex flex-wrap gap-1.5">
+                    {keywords.map((kw, i) => (
+                      <span key={i} className="glass-card px-2 py-0.5 rounded-full text-xs">
+                        {kw}
+                      </span>
+                    ))}
+                  </div>
+                </div>
+              )}
+            </div>
+          )}
         </div>
       )}
     </main>

frontend/src/components/Channels.tsx

@@ -399,7 +399,7 @@ export default function Channels({
     return (
       <>
         {tabs}
-        <ChannelDiscovery canWrite={canWrite} onOpenWizard={onOpenWizard} />
+        <ChannelDiscovery canWrite={canWrite} onOpenWizard={onOpenWizard} onViewChannel={onViewChannel} />
       </>
     );
   }

frontend/src/i18n/locales/de/channel.json

@@ -19,5 +19,9 @@
   "noDescription": "Dieser Kanal hat keine Beschreibung.",
   "block": "Kanal blockieren",
   "unblock": "Blockierung aufheben",
-  "blockedBadge": "Blockiert"
+  "blockedBadge": "Blockiert",
+  "country": "Land",
+  "language": "Sprache",
+  "topics": "Themen",
+  "keywords": "Schlagwörter"
 }

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

@@ -19,5 +19,9 @@
   "noDescription": "This channel has no description.",
   "block": "Block channel",
   "unblock": "Unblock channel",
-  "blockedBadge": "Blocked"
+  "blockedBadge": "Blocked",
+  "country": "Country",
+  "language": "Language",
+  "topics": "Topics",
+  "keywords": "Keywords"
 }

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

@@ -19,5 +19,9 @@
   "noDescription": "Ennek a csatornának nincs leírása.",
   "block": "Csatorna tiltása",
   "unblock": "Tiltás feloldása",
-  "blockedBadge": "Tiltva"
+  "blockedBadge": "Tiltva",
+  "country": "Ország",
+  "language": "Nyelv",
+  "topics": "Témák",
+  "keywords": "Kulcsszavak"
 }

frontend/src/lib/api.ts

@@ -96,6 +96,9 @@ export interface ChannelDetail {
   published_at: string | null;
   external_links: ChannelLink[];
   country: string | null;
+  default_language: string | null;
+  topic_categories: string[];
+  keywords: string | null;
   subscribed: boolean;
   explored: boolean;
   blocked: boolean;