feat(feed,channels): "No tag" filter for untagged channels (E8·S1)

Filter to channels you haven't personally tagged in the channel manager
(no user-owned ChannelTag; auto language/topic tags don't count):

- Feed: a "No tag" sentinel in the "Your tags" sidebar combobox (exclusive
  with real tag picks) + a removable "Untagged" chip; new `untagged` bool
  feed param / `notag` URL key, persisted + coerced on every filter path.
- Channel manager: a virtual "No tag" chip in the tag-chip row filters the
  table to untagged channels (client-side, shared NO_TAG_SENTINEL).

Backend `untagged` is a plain channel-level narrowing, so feed_summary keeps
it applied in the base pass — the count/facet lockstep holds with no mirror.

Note: item E (per-tag counts) and item D (Any/All toggle) were already
shipped; S1 delivers only item B.

backend/app/feedquery.py

@@ -100,6 +100,11 @@ def serialize(row) -> dict:
     }
 
 
+def _tag_visible(user: User):
+    """A ChannelTag row this user may see: a shared system tag (user_id NULL) or their own."""
+    return or_(ChannelTag.user_id.is_(None), ChannelTag.user_id == user.id)
+
+
 def tags_by_category(db: Session, tag_ids: list[int]) -> dict[str, list[int]]:
     """Group tag ids by their category (language/topic/other). The single source for the category split
     shared by the feed's tag WHERE (filtered_query) and the facet/count summary (feed_summary), so the
@@ -118,6 +123,7 @@ def filtered_query(
     *,
     tags: list[int],
     tag_modes: dict[str, str],
+    untagged: bool = False,
     channel_ids: list[str],
     q: str | None,
     min_duration: int | None,
@@ -294,7 +300,7 @@ def filtered_query(
         # selections but still honours the other categories' filters).
         if exclude_tag_category:
             by_category.pop(exclude_tag_category, None)
-        visible = or_(ChannelTag.user_id.is_(None), ChannelTag.user_id == user.id)
+        visible = _tag_visible(user)
         for category, ids in by_category.items():
             if tag_modes.get(category, "or") == "and" and len(ids) > 1:
                 sub = (
@@ -307,6 +313,18 @@ def filtered_query(
                 sub = select(ChannelTag.channel_id).where(ChannelTag.tag_id.in_(ids), visible)
             query = query.where(Video.channel_id.in_(sub))
 
+    # "No tag" filter (item B): keep only channels the USER has not personally tagged in the channel
+    # manager — i.e. channels with no ChannelTag row owned by this user (user_id == me, source "user").
+    # System/auto tags (user_id NULL) don't count: this is "channels I haven't tagged yet". It's a plain
+    # channel-level narrowing (like channel_ids/date), NOT a tag-category selection, so feed_summary
+    # leaves it applied in the base pass and needs no mirror in passes().
+    if untagged:
+        query = query.where(
+            Video.channel_id.notin_(
+                select(ChannelTag.channel_id).where(ChannelTag.user_id == user.id)
+            )
+        )
+
     # Content type: Normal / Shorts / Live·Upcoming as a union of enabled types.
     # Explicit Watched/Saved/Hidden views show every type so nothing goes missing.
     explicit_view = show in ("watched", "hidden")
@@ -355,8 +373,9 @@ def feed_summary(db: Session, user: User, **params) -> dict:
     within, a category in "and" mode requires ALL its selected tags)."""
     tag_modes = params.get("tag_modes", {})
 
-    # ONE pass: per-channel video counts for the base filter, tags stripped so every candidate channel
-    # is present to facet over.
+    # ONE pass: per-channel video counts for the base filter, the positive tag filter stripped so every
+    # candidate channel is present to facet over. The "No tag" (untagged) filter is a plain channel-level
+    # narrowing, so it STAYS applied here (not stripped) and the facets naturally drill down within it.
     base, _rank = filtered_query(db, user, **{**params, "tags": []})
     ch_col = base.with_only_columns(Video.channel_id).subquery()
     channel_counts: dict[str, int] = dict(
@@ -386,7 +405,8 @@ def feed_summary(db: Session, user: User, **params) -> dict:
 
     def passes(ch_tags: set[int], exclude_cat: str | None) -> bool:
         # The Python mirror of filtered_query's SQL tag block (AND across categories, OR within,
-        # topic-AND requires all selected) — keep in lockstep; see the ⚠️ note there.
+        # topic-AND requires all selected) — keep in lockstep; see the ⚠️ note there. (The "No tag"
+        # filter is applied in the base query above, so it needs no mirror here.)
         for cat, sel in selected_by_cat.items():
             if cat == exclude_cat:
                 continue

backend/app/routes/feed.py

@@ -53,6 +53,8 @@ def _feed_params(
     tag_mode_language: str = "or",
     tag_mode_topic: str = "or",
     tag_mode_other: str = "or",
+    # "No tag" filter: keep only channels the user has not personally tagged (no user-owned ChannelTag).
+    untagged: bool = False,
     channel_ids: list[str] = Query(default=[]),
     q: str | None = None,
     min_duration: int | None = None,
@@ -74,6 +76,7 @@ def _feed_params(
             "topic": tag_mode_topic,
             "other": tag_mode_other,
         },
+        "untagged": untagged,
         "channel_ids": channel_ids,
         "q": q,
         "min_duration": min_duration,

backend/tests/test_feed_views.py

@@ -162,11 +162,45 @@ _SUMMARY_CASES = [
     "show=all&tags={O1}&tags={O2}&tag_mode_other=and",
     "show=all&tags={U1}",  # user-owned tag (visibility == user.id branch)
     "show=all&tags={U1}&tags={L1}",  # user tag AND a system tag, cross-category
+    # "No tag" filter (item B): channels with no USER tag. It stays applied in the base pass, so the
+    # facet/count lockstep must still hold with it on (alone, and combined with a positive tag filter).
+    "show=all&untagged=true",
+    "show=all&untagged=true&tags={L1}",
     "show=all&q=clip",
     "show=unwatched",
 ]
 
 
+def test_untagged_filter_keeps_only_channels_the_user_has_not_tagged(db, as_user, make_user):
+    """The "No tag" filter (item B): `untagged=true` keeps only channels with NO tag the USER personally
+    attached (no user-owned ChannelTag). System/auto tags (user_id NULL) don't count, and another user's
+    tag on the same channel doesn't either."""
+    user = make_user(email="untagged@example.com")
+    other = make_user(email="someone-else@example.com")
+    mine = Tag(user_id=user.id, name="Fav", category="other")
+    sys_topic = Tag(user_id=None, name="Tech", category="topic")
+    theirs = Tag(user_id=other.id, name="TheirTag", category="other")
+    db.add_all([mine, sys_topic, theirs])
+    chans = {c: Channel(id=c, title=c, subscriber_count=10) for c in ("chMine", "chSys", "chNone")}
+    db.add_all(chans.values())
+    db.flush()
+    # chMine: the user's own tag → tagged. chSys: only a system tag + another user's tag → still
+    # "untagged" for THIS user. chNone: nothing at all → untagged.
+    db.add(ChannelTag(channel_id="chMine", tag_id=mine.id, user_id=user.id, source="user"))
+    db.add(ChannelTag(channel_id="chSys", tag_id=sys_topic.id, user_id=None, source="auto"))
+    db.add(ChannelTag(channel_id="chSys", tag_id=theirs.id, user_id=other.id, source="user"))
+    for cid in chans:
+        db.add(Subscription(user_id=user.id, channel_id=cid, priority=0, hidden=False))
+        db.add(_video(f"{cid}v", cid, f"{cid} clip"))
+    db.commit()
+    client = as_user(user)
+
+    # Off: every subscribed channel shows.
+    assert _feed_ids(client, "show=all") == {"chMinev", "chSysv", "chNonev"}
+    # On: only channels the user has NOT personally tagged (a system tag / another user's tag don't count).
+    assert _feed_ids(client, "show=all&untagged=true") == {"chSysv", "chNonev"}
+
+
 @pytest.mark.parametrize("case", _SUMMARY_CASES)
 def test_feed_summary_matches_count_plus_facets(db, as_user, make_user, case):
     # /feed/summary must return byte-identical numbers to the old /feed/count + /facets it replaces,

frontend/src/components/Channels.tsx

@@ -4,7 +4,7 @@ import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { qk } from "../lib/queryKeys";
 import { Ban, Eye, EyeOff, History, LayoutGrid, Pencil, RefreshCw, Table, X } from "lucide-react";
 import ExcludedChannelList from "./ExcludedChannelList";
-import { api, type ManagedChannel } from "../lib/api";
+import { api, NO_TAG_SENTINEL, type ManagedChannel } from "../lib/api";
 import { notifyYouTubeActionError } from "../lib/youtubeErrors";
 import { accountKey, LS } from "../lib/storage";
 import { buildChannelColumns, applySyncFilter } from "./channelColumns";
@@ -217,11 +217,18 @@ export default function Channels() {
   // funnel share ONE state and stay in sync (bidirectional). Toggling a chip rewrites `filters.tags`;
   // filterRows / DataTable then applies it. Channel-name search stays separate (the shared top box).
   const tagFilter = Array.isArray(filters.tags) ? filters.tags : [];
+  // Picking a real tag drops the "No tag" sentinel (item B) — they're mutually exclusive, as in the feed.
   const toggleTagFilter = (tagId: number) => {
     const id = String(tagId);
-    const next = tagFilter.includes(id) ? tagFilter.filter((x) => x !== id) : [...tagFilter, id];
+    const base = tagFilter.filter((x) => x !== NO_TAG_SENTINEL);
+    const next = base.includes(id) ? base.filter((x) => x !== id) : [...base, id];
     setFilters({ ...filters, tags: next });
   };
+  // The "No tag" chip: filter the table to channels you haven't personally tagged yet. Exclusive with
+  // real tag chips (clicking it drops them); the Tags column's test reads the sentinel (channelColumns).
+  const noTagOn = tagFilter.includes(NO_TAG_SENTINEL);
+  const toggleNoTagFilter = () =>
+    setFilters({ ...filters, tags: noTagOn ? [] : [NO_TAG_SENTINEL] });
   // A focus-channel intent (header "without full history" / tag manager) seeds the search box.
   useEffect(() => {
     if (focusChannelName) setSearch(focusChannelName);
@@ -451,6 +458,13 @@ export default function Channels() {
                     {tg.name}
                   </button>
                 ))}
+                <button
+                  onClick={toggleNoTagFilter}
+                  aria-pressed={noTagOn}
+                  className={filterChipClass}
+                >
+                  {t("channels.tags.noTag")}
+                </button>
                 {tagFilter.length > 0 && (
                   <button
                     onClick={() => setFilters({ ...filters, tags: [] })}

frontend/src/components/FeedFiltersProvider.tsx

@@ -13,6 +13,7 @@ import {
   api,
   getActiveAccount,
   coerceTagModes,
+  coerceUntagged,
   DEFAULT_TAG_MODES,
   type FeedFilters,
 } from "../lib/api";
@@ -39,6 +40,7 @@ import { useNavigation } from "./NavigationProvider";
 const DEFAULT_FILTERS: FeedFilters = {
   tags: [],
   tagModes: DEFAULT_TAG_MODES,
+  untagged: false,
   channelIds: [],
   q: "",
   sort: "newest",
@@ -74,7 +76,12 @@ export function loadAccountFilters(id: number | null): FeedFilters {
   // (all "or"), which coerceTagModes prefers over the legacy scalar and would mask it.
   if (hasStored && fKey) {
     const raw = readJSON<Partial<FeedFilters>>(fKey, {});
-    return { ...DEFAULT_FILTERS, ...raw, tagModes: coerceTagModes(raw) };
+    return {
+      ...DEFAULT_FILTERS,
+      ...raw,
+      tagModes: coerceTagModes(raw),
+      untagged: coerceUntagged(raw),
+    };
   }
   return { ...DEFAULT_FILTERS };
 }

frontend/src/components/SavedViewsProvider.tsx

@@ -14,6 +14,7 @@ import {
   api,
   coercePlexFilters,
   coerceTagModes,
+  coerceUntagged,
   getActiveAccount,
   plexFiltersSignature,
   type FeedFilters,
@@ -42,6 +43,7 @@ export const asFilters = (raw: FeedFilters): FeedFilters => ({
   tags: raw.tags ?? [],
   channelIds: raw.channelIds ?? [],
   tagModes: coerceTagModes(raw),
+  untagged: coerceUntagged(raw),
 });
 
 type ViewSource = "feed" | "plex";

frontend/src/components/Sidebar.tsx

@@ -3,7 +3,7 @@ import { useTranslation } from "react-i18next";
 import { keepPreviousData, useQuery } from "@tanstack/react-query";
 import { qk } from "../lib/queryKeys";
 import { SlidersHorizontal } from "lucide-react";
-import { api, type FeedFilters, type Tag, type TagCategory } from "../lib/api";
+import { api, NO_TAG_SENTINEL, type FeedFilters, type Tag, type TagCategory } from "../lib/api";
 import { defaultLayout, type PanelLayout } from "../lib/panelLayout";
 import { useDebounced } from "../lib/useDebounced";
 import { useActiveFilters } from "../lib/useActiveFilters";
@@ -104,6 +104,41 @@ export default function Sidebar({
   const setTagMode = (category: TagCategory, mode: "or" | "and") =>
     setFilters({ ...filters, tagModes: { ...filters.tagModes, [category]: mode } });
 
+  // The "Your tags" combobox carries the "No tag" sentinel (item B) at the top: selecting it filters to
+  // channels you HAVEN'T personally tagged in the channel manager (`filters.untagged`). It's mutually
+  // exclusive with picking real user tags — choosing it clears your tag picks, and picking a tag clears
+  // it. Language/Topic are auto/system tags, so "No tag" is meaningless there and only lives here.
+  function userTagsCombo(): ReactNode {
+    const noneOn = !!filters.untagged;
+    const inList = (id: number) => userTags.some((tg) => tg.id === id);
+    const onChange = (next: string[]) => {
+      if (next.includes(NO_TAG_SENTINEL) && !noneOn) {
+        setFilters({ ...filters, tags: filters.tags.filter((id) => !inList(id)), untagged: true });
+      } else {
+        const reals = next.filter((v) => v !== NO_TAG_SENTINEL).map(Number);
+        setFilters({
+          ...filters,
+          tags: [...filters.tags.filter((id) => !inList(id)), ...reals],
+          untagged: false,
+        });
+      }
+    };
+    return (
+      <Combobox
+        label={t("sidebar.widget.tags")}
+        options={[
+          { value: NO_TAG_SENTINEL, label: t("sidebar.noTagOption") },
+          ...visibleChips(userTags).map(tagOption),
+        ]}
+        selected={noneOn ? [NO_TAG_SENTINEL] : selectedIn(userTags)}
+        onChange={onChange}
+        emptyText={t("sidebar.noMatchingTags")}
+        matchMode={filters.tagModes.other}
+        onMatchModeChange={(m) => setTagMode("other", m)}
+      />
+    );
+  }
+
   // The badge counts exactly what the chip row above the feed shows — same list, so they can't
   // disagree about what's applied.
   const activeCount = useActiveFilters(filters, setFilters).length;
@@ -124,7 +159,7 @@ export default function Sidebar({
         return (
           <DateFilterSelect filters={filters} setFilters={setFilters} presets={DATE_PRESETS} />
         );
-      case "language": {
+      case "language":
         return (
           <Combobox
             label={t("sidebar.widget.language")}
@@ -136,8 +171,7 @@ export default function Sidebar({
             onMatchModeChange={(m) => setTagMode("language", m)}
           />
         );
-      }
-      case "topic": {
+      case "topic":
         return (
           <Combobox
             label={t("sidebar.widget.topic")}
@@ -149,22 +183,10 @@ export default function Sidebar({
             onMatchModeChange={(m) => setTagMode("topic", m)}
           />
         );
-      }
-      case "tags": {
+      case "tags":
         // The widget's own "Manage" trigger is its title (see the PanelItem onTitleClick below), so the
-        // body is just the picker.
-        return (
-          <Combobox
-            label={t("sidebar.widget.tags")}
-            options={visibleChips(userTags).map(tagOption)}
-            selected={selectedIn(userTags)}
-            onChange={(next) => setTagSelection(userTags, next)}
-            emptyText={t("sidebar.noMatchingTags")}
-            matchMode={filters.tagModes.other}
-            onMatchModeChange={(m) => setTagMode("other", m)}
-          />
-        );
-      }
+        // body is just the picker — user tags plus the "No tag" sentinel.
+        return userTagsCombo();
       default:
         return null;
     }

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

@@ -5,8 +5,8 @@
 // "fully" | "needsFull" | "" vocab + predicate — asserted here so a regression can't silently change
 // which channels the top chips show.
 import { describe, it, expect } from "vitest";
-import { applySyncFilter } from "./channelColumns";
-import { type ManagedChannel } from "../lib/api";
+import { applySyncFilter, tagsColumnTest } from "./channelColumns";
+import { NO_TAG_SENTINEL, type ManagedChannel } from "../lib/api";
 
 const ch = (over: Partial<ManagedChannel>): ManagedChannel => ({
   id: "c",
@@ -51,3 +51,23 @@ describe("applySyncFilter", () => {
     expect(applySyncFilter(rows, "needsFull").map((r) => r.id)).toEqual(["recentOnly", "none"]);
   });
 });
+
+describe("tagsColumnTest (item B — 'No tag')", () => {
+  const tagged = ch({ id: "tagged", tag_ids: [1, 2] });
+  const untagged = ch({ id: "untagged", tag_ids: [] });
+
+  it("the No-tag sentinel keeps only channels with no user tag", () => {
+    expect(tagsColumnTest(tagged, [NO_TAG_SENTINEL])).toBe(false);
+    expect(tagsColumnTest(untagged, [NO_TAG_SENTINEL])).toBe(true);
+  });
+
+  it("real tag values match ANY selected id (sentinel absent)", () => {
+    expect(tagsColumnTest(tagged, ["2"])).toBe(true);
+    expect(tagsColumnTest(tagged, ["3"])).toBe(false);
+    expect(tagsColumnTest(untagged, ["1"])).toBe(false);
+  });
+
+  it("the sentinel wins if it somehow co-exists with real ids", () => {
+    expect(tagsColumnTest(tagged, [NO_TAG_SENTINEL, "1"])).toBe(false);
+  });
+});

frontend/src/components/channelColumns.tsx

@@ -2,7 +2,7 @@ import type { ComponentProps } from "react";
 import type { TFunction } from "i18next";
 import { useTranslation } from "react-i18next";
 import { Check, Eye, EyeOff, History, UserMinus } from "lucide-react";
-import type { ManagedChannel } from "../lib/api";
+import { NO_TAG_SENTINEL, type ManagedChannel } from "../lib/api";
 import { formatCountOrDash, formatTotalHours, relativeTime } from "../lib/format";
 import type { Column } from "./DataTable";
 import Tooltip from "./Tooltip";
@@ -42,6 +42,14 @@ export function applySyncFilter(rows: ManagedChannel[], value: unknown): Managed
   return rows;
 }
 
+/** The Tags column filter predicate (item B): the "No tag" sentinel keeps channels the user hasn't
+ *  personally tagged (empty `tag_ids`); it's exclusive with real tag picks (the chip row enforces that),
+ *  so when present it wins. Otherwise a channel passes if it carries ANY selected tag id. */
+export function tagsColumnTest(c: ManagedChannel, values: string[]): boolean {
+  if (values.includes(NO_TAG_SENTINEL)) return c.tag_ids.length === 0;
+  return values.some((v) => c.tag_ids.includes(Number(v)));
+}
+
 // The Stored count, with a "fully synced" ✓ charm to the left of the number when recent uploads and
 // full history are both in — folding the retired Sync column's at-a-glance status into the value it
 // describes. Full detail stays in the hover tooltip.
@@ -289,7 +297,7 @@ export function buildChannelColumns(deps: ChannelColumnDeps): Column<ManagedChan
       filter: {
         kind: "multi",
         options: userTags.map((tg) => ({ value: String(tg.id), label: tg.name })),
-        test: (c, values) => values.some((v) => c.tag_ids.includes(Number(v))),
+        test: tagsColumnTest,
       },
       render: (c) => (
         <ChannelTagsControl

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

@@ -51,7 +51,8 @@
     "noneYet": "No tags yet — create one below.",
     "create": "Create tag",
     "createPlaceholder": "New tag…",
-    "createFailed": "Could not create the tag."
+    "createFailed": "Could not create the tag.",
+    "noTag": "No tag"
   },
   "loading": "Loading channels…",
   "empty": "No channels.",

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

@@ -3,6 +3,7 @@
     "label": "Filtered by",
     "remove": "Remove filter: {{name}}",
     "contentNone": "No content types",
+    "untagged": "Untagged",
     "count_one": "{{count}} filter",
     "count_other": "{{count}} filters",
     "moreCount_one": "{{count}} more filter",

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

@@ -27,6 +27,7 @@
   "clearDates": "clear dates",
   "reshuffle": "Reshuffle",
   "noMatchingTags": "No matching tags here",
+  "noTagOption": "No tag",
   "manageTags": "Manage",
   "widget": {
     "savedviews": "Saved views",

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

@@ -51,7 +51,8 @@
     "noneYet": "Még nincs címke — hozz létre egyet lent.",
     "create": "Címke létrehozása",
     "createPlaceholder": "Új címke…",
-    "createFailed": "A címke létrehozása nem sikerült."
+    "createFailed": "A címke létrehozása nem sikerült.",
+    "noTag": "Nincs címke"
   },
   "loading": "Csatornák betöltése…",
   "empty": "Nincsenek csatornák.",

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

@@ -3,6 +3,7 @@
     "label": "Szűrve",
     "remove": "Szűrő eltávolítása: {{name}}",
     "contentNone": "Nincs tartalomtípus",
+    "untagged": "Címkézetlen",
     "count_one": "{{count}} szűrő",
     "count_other": "{{count}} szűrő",
     "moreCount_one": "még {{count}} szűrő",

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

@@ -27,6 +27,7 @@
   "clearDates": "dátumok törlése",
   "reshuffle": "Újrakeverés",
   "noMatchingTags": "Nincs ide illő címke",
+  "noTagOption": "Nincs címke",
   "manageTags": "Kezelés",
   "widget": {
     "savedviews": "Mentett nézetek",

frontend/src/lib/api.ts

@@ -32,7 +32,13 @@ export type * from "./api/setup";
 import { feedApi } from "./api/feed";
 export type * from "./api/feed";
 export type * from "./api/tagModes";
-export { DEFAULT_TAG_MODES, TAG_CATEGORIES, coerceTagModes } from "./api/tagModes";
+export {
+  DEFAULT_TAG_MODES,
+  TAG_CATEGORIES,
+  NO_TAG_SENTINEL,
+  coerceTagModes,
+  coerceUntagged,
+} from "./api/tagModes";
 import { channelsApi } from "./api/channels";
 export type * from "./api/channels";
 import { syncApi } from "./api/sync";

frontend/src/lib/api/feed.ts

@@ -71,6 +71,9 @@ export interface FeedFilters {
   // Library (scope "all") only — provenance filter: "organic" (default) hides search-
   // discovered videos, "all" mixes them in, "search" shows only them. Ignored for "my".
   librarySource?: "organic" | "all" | "search" | "plex";
+  /** "No tag" filter (item B): keep only channels the user has NOT personally tagged in the channel
+   *  manager (no user-owned ChannelTag). Auto/system tags don't count. */
+  untagged?: boolean;
   /** OR-ed together: a video from ANY of these passes, and every other filter still applies. */
   channelIds: string[];
   maxAgeDays?: number;
@@ -89,6 +92,7 @@ function filterParams(f: FeedFilters): URLSearchParams {
   for (const cat of TAG_CATEGORIES) {
     if (f.tagModes[cat] === "and") p.set(`tag_mode_${cat}`, "and");
   }
+  if (f.untagged) p.set("untagged", "true");
   if (f.q) p.set("q", f.q);
   p.set("scope", f.scope);
   p.set("show_normal", String(f.includeNormal));

frontend/src/lib/api/tagModes.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from "vitest";
-import { coerceTagModes, DEFAULT_TAG_MODES } from "./tagModes";
+import { coerceTagModes, coerceUntagged, DEFAULT_TAG_MODES } from "./tagModes";
 
 // coerceTagModes runs on every persisted saved-view blob (SavedViewsProvider.asFilters), on the URL
 // parse, and on the localStorage seed — the single migration point for the legacy global `tagMode`.
@@ -40,3 +40,15 @@ describe("coerceTagModes", () => {
     expect(coerceTagModes({ tagModes: { language: 1 as unknown as "or" } }).language).toBe("or");
   });
 });
+
+// coerceUntagged guards the "No tag" (item B) flag on the same persisted/URL/saved-view paths.
+describe("coerceUntagged", () => {
+  it("is true only for an explicit untagged:true", () => {
+    expect(coerceUntagged({ untagged: true })).toBe(true);
+    expect(coerceUntagged(undefined)).toBe(false);
+    expect(coerceUntagged({})).toBe(false);
+    expect(coerceUntagged(null)).toBe(false);
+    expect(coerceUntagged({ untagged: "true" })).toBe(false);
+    expect(coerceUntagged({ untagged: ["other"] })).toBe(false);
+  });
+});

frontend/src/lib/api/tagModes.ts

@@ -10,6 +10,11 @@ export type TagModes = Record<TagCategory, TagMode>;
 export const TAG_CATEGORIES: readonly TagCategory[] = ["language", "topic", "other"];
 export const DEFAULT_TAG_MODES: TagModes = { language: "or", topic: "or", other: "or" };
 
+/** UI sentinel for the "No tag" (item B) option — the feed's user-tags combobox and the channel
+ *  manager's tag chip row both use it to mean "channels I haven't personally tagged". Not a real tag
+ *  id (those are numeric strings), so it can never collide with one. */
+export const NO_TAG_SENTINEL = "__none__";
+
 /** Normalise a persisted/shared filter's tag match into the per-category shape, migrating the legacy
  *  global `tagMode` (which only ever affected topics) into the topic slot. */
 export function coerceTagModes(raw: unknown): TagModes {
@@ -22,3 +27,8 @@ export function coerceTagModes(raw: unknown): TagModes {
   };
   return { language: pick("language"), topic: pick("topic"), other: pick("other") };
 }
+
+/** Normalise a persisted/shared filter's "No tag" (item B) flag to a boolean. */
+export function coerceUntagged(raw: unknown): boolean {
+  return (raw as { untagged?: unknown } | null)?.untagged === true;
+}

frontend/src/lib/urlState.dom.test.ts

@@ -140,4 +140,12 @@ describe("filterParamUpdates", () => {
     const back = paramsToFilters(new URLSearchParams("tagmode=and"), DEFAULTS);
     expect(back.tagModes).toEqual({ language: "or", topic: "and", other: "or" });
   });
+
+  it("round-trips the 'No tag' (untagged) flag; emitted only when on", () => {
+    expect(filtersToParams({ ...DEFAULTS, untagged: true }).get("notag")).toBe("1");
+    expect(filtersToParams({ ...DEFAULTS, untagged: false }).has("notag")).toBe(false);
+    expect(paramsToFilters(new URLSearchParams("notag=1"), DEFAULTS).untagged).toBe(true);
+    // Absent → the base value is left untouched (undefined here, i.e. off).
+    expect(paramsToFilters(new URLSearchParams(""), DEFAULTS).untagged).toBeUndefined();
+  });
 });

frontend/src/lib/urlState.ts

@@ -20,6 +20,7 @@ const KEYS = [
   "tagmode_topic",
   "tagmode_other",
   "tagmode", // legacy global (topic-only) — still recognised so old shared links resolve
+  "notag",
   "channel",
   "maxage",
   "from",
@@ -44,6 +45,7 @@ export function filtersToParams(f: FeedFilters): URLSearchParams {
   for (const cat of TAG_CATEGORIES) {
     if (f.tagModes[cat] === "and") p.set(`tagmode_${cat}`, "and");
   }
+  if (f.untagged) p.set("notag", "1");
   if (f.channelIds.length) p.set("channel", f.channelIds.join(","));
   if (f.maxAgeDays) p.set("maxage", String(f.maxAgeDays));
   if (f.dateFrom) p.set("from", f.dateFrom);
@@ -95,6 +97,7 @@ export function paramsToFilters(params: URLSearchParams, base: FeedFilters): Fee
     topic: params.get("tagmode_topic") === "and" || params.get("tagmode") === "and" ? "and" : "or",
     other: params.get("tagmode_other") === "and" ? "and" : "or",
   };
+  if (params.has("notag")) f.untagged = params.get("notag") === "1";
   f.channelIds = (params.get("channel") ?? "").split(",").filter(Boolean);
   f.maxAgeDays = num(params.get("maxage"));
   f.dateFrom = params.get("from") || undefined;

frontend/src/lib/useActiveFilters.ts

@@ -15,6 +15,7 @@ export interface ActiveFilter {
 const DEFAULT_SIDEBAR_FILTERS: Omit<FeedFilters, "q" | "scope"> = {
   tags: [],
   tagModes: DEFAULT_TAG_MODES,
+  untagged: false,
   channelIds: [],
   sort: "newest",
   includeNormal: true,
@@ -66,6 +67,15 @@ export function useActiveFilters(
     });
   }
 
+  // "No tag" (item B): channels the user hasn't personally tagged. One removable chip.
+  if (filters.untagged) {
+    out.push({
+      key: "untagged",
+      label: t("feed.chips.untagged"),
+      remove: () => setFilters({ ...filters, untagged: false }),
+    });
+  }
+
   if (filters.show !== "unwatched") {
     out.push({
       key: "show",