fix(e24): the Home surface's three UAT findings — Back, the reroll, and a show card

All three were measured before they were touched, and the diagnosis moved twice.

**Back from a Plex title played off Home landed on the Plex module's root.** One
click pushed three history entries: the page navigation, the sub-view opened by
the `jumpTo` hand-off, and — under StrictMode, whose effect body runs twice
before `setJumpTo(null)` re-renders — that same sub-view a second time. So the
first Back visibly did nothing and the second stranded the user on a Discover
page they had never visited.

A cross-module hand-off is the CONTINUATION of the navigation that brought you
there, not a second navigation, so it now REPLACES the page entry instead of
stacking on it (`useHistorySubview.open(view, {replace})`, asked for by the jump
target). Replacing is also idempotent, which is what disarms the StrictMode
double-run. The intent rides on `PlexJumpTarget` rather than being inferred,
because the header typeahead jumps from INSIDE the module, where the entry being
replaced would be a sub-view the user really was looking at.

**"Mást kérek" cycled nine cards and never left the resume tier.** Measured:
twelve presses, nine distinct titles, period nine, every one `tier: "resume"` —
the shelf and the surprise tier were unreachable by pressing the button. Two
causes multiplied: the tiers were tried in a fixed priority order over a 20-row
resume rail, so the button just walked down it; and the client's rolling
exclusion window of 8 guaranteed the wrap.

The press count now rotates which tier answers first (`start`), so each press
offers a different KIND of answer — the user's call, given the choice between
that, a wider window, and a surprise-only reroll. The fallthrough is kept, so a
press does not come back empty because the tier it led with had nothing. The
window is matched to the server's own cap rather than a smaller number of ours.

**A half-watched series on Home opened the show page.** A movie already went
straight to the player; only shows did not — and the comfort shelf and the hero
both resolved a show to its next episode while this rail alone did not, handing
back six seasons to choose between. The rail row now carries `next`, and the
client already played `next ?? card`, so this is a backend fix.

Affording it needed `queries.next_episode` to stop loading every episode of the
show into Python to pick one of them (236 rows for Friends, 227 for JAG) — three
ordered LIMIT 1 probes instead. The show→episode rule now lives in ONE function
(`rails.playable`), which is what the shelf, the hero and the rail all call; two
implementations are how they came to disagree.

Ten mutations run, all ten red for the right test — including a first pass where
the press count reached `api.discoverPick` and stopped there, invisible because
every Home test mocks that module. The slice now has its own URL test.

Verified in a clean browser tab against the live account: one Back returns to
Home, the rotation gives resume/comfort/surprise across nine presses with no
repeat, and Westworld opens at S1E1 rather than at its show page.

backend/app/discover/hero.py

@@ -10,6 +10,10 @@ Three tiers, tried in order:
    anything we could infer.
 3. **surprise** — a seeded draw from what is unseen and fits.
 
+That order is the PAGE's answer. "Mást kérek" rotates it (`start`), so each press offers a different
+KIND of answer rather than the next row of the same list — the user's call, 2026-09-06, after the
+button was measured cycling nine resume cards and never once reaching the shelf.
+
 The tier travels with the card so the client can label it honestly ("Ott hagytad abba" vs "A
 polcodról" vs "Meglepetés") instead of guessing from the shape of the payload — a kicker that says
 "where you left off" over a film the user has never opened is exactly the kind of quiet lie the house
@@ -22,30 +26,18 @@ answer.
 
 from sqlalchemy.orm import Session
 
-from app.discover import cards, pins, queries, rails
+from app.discover import cards, pins, rails
 from app.discover.budget import fits
-from app.models import PlexShow, User
-from app.plex.lookups import by_rating_key
+from app.models import User
 
 HERO_TIERS = ("resume", "comfort", "surprise")
 
-# How deep the surprise tier draws before giving up. The client's exclusion window is 8 (see
-# `Home.tsx`), so a draw of 12 can always step past a full window of already-shown picks.
+# How deep the surprise tier draws before giving up. Deliberately deeper than one, so an excluded
+# pick moves the tier along instead of emptying it (the shuffle is seeded — the same seed always
+# hands back the same order, so without the headroom "already shown" would mean "nothing left").
 SURPRISE_DRAW = 12
 
 
-def _playable(db: Session, uid: int, card: dict) -> dict | None:
-    """A hero has to have a Play button, so a Plex SHOW is resolved to the episode that would start.
-    Everything else already plays itself. None when the show has no episodes mirrored yet."""
-    if not (card.get("source") == "plex" and card.get("kind") == "show"):
-        return card
-    sh = by_rating_key(db, PlexShow, card["id"])
-    if sh is None:
-        return None
-    ep = queries.next_episode(db, uid, sh.id)
-    return cards.from_plex(ep) if ep else None
-
-
 def pick(
     db: Session,
     user: User,
@@ -55,6 +47,7 @@ def pick(
     resume: list[dict] | None = None,
     shelf: list[dict] | None = None,
     exclude: set[str] | None = None,
+    start: int = 0,
 ) -> dict | None:
     """`{"tier": ..., "card": ...}`, or None when nothing at all fits.
 
@@ -66,25 +59,46 @@ def pick(
     tier: the resume tier deterministically returns the most recently progressed thing that fits, so
     pressing reroll on a user who has something half-finished handed back the identical card and the
     button looked dead (measured in the browser, 2026-09-06). Skipping the cards already shown makes
-    every press produce a different answer, at every tier."""
+    every press produce a different answer, at every tier.
+
+    `start` ROTATES which tier is tried first — 0 keeps the priority order (the page's own first
+    answer), 1 leads with comfort, 2 with surprise. Exclusion alone was not enough: the resume rail
+    holds up to 20 rows, so the button walked down it and never reached the shelf or a surprise at
+    all (measured, 2026-09-06: twelve presses returned nine cards, every one of them `resume`). The
+    fallthrough is kept, so a press does not come back empty just because the tier it led with has
+    nothing to offer."""
     skip = exclude or set()
-    for card in rails.continue_watching(db, user) if resume is None else resume:
-        playable = _playable(db, user.id, card)
-        # Excluded on the card the USER saw (the show), not only on what it resolves to, so a
-        # rerolled-past show does not come straight back as its own next episode.
-        if cards.key(card) in skip or (playable is not None and cards.key(playable) in skip):
-            continue
-        if playable is not None and fits(playable["remaining_seconds"], budget):
-            return {"tier": "resume", "card": playable}
 
-    for card in pins.playables(pins.shelf(db, user) if shelf is None else shelf):
-        if cards.key(card) not in skip and fits(card["remaining_seconds"], budget):
-            return {"tier": "comfort", "card": card}
+    def _resume() -> dict | None:
+        for card in rails.continue_watching(db, user) if resume is None else resume:
+            playable = rails.playable(db, user.id, card)
+            # Excluded on the card the USER saw (the show), not only on what it resolves to, so a
+            # rerolled-past show does not come straight back as its own next episode.
+            if cards.key(card) in skip or (playable is not None and cards.key(playable) in skip):
+                continue
+            if playable is not None and fits(playable["remaining_seconds"], budget):
+                return playable
+        return None
 
-    # A wider draw than the one card we need: the shuffle is seeded, so without the headroom an
-    # excluded pick would leave the tier empty rather than move past it.
-    for card in rails.surprise(db, user, budget, seed, limit=SURPRISE_DRAW):
-        if cards.key(card) not in skip:
-            return {"tier": "surprise", "card": card}
+    def _comfort() -> dict | None:
+        for card in pins.playables(pins.shelf(db, user) if shelf is None else shelf):
+            if cards.key(card) not in skip and fits(card["remaining_seconds"], budget):
+                return card
+        return None
+
+    def _surprise() -> dict | None:
+        # A wider draw than the one card we need: the shuffle is seeded, so without the headroom an
+        # excluded pick would leave the tier empty rather than move past it.
+        for card in rails.surprise(db, user, budget, seed, limit=SURPRISE_DRAW):
+            if cards.key(card) not in skip:
+                return card
+        return None
+
+    tiers = {"resume": _resume, "comfort": _comfort, "surprise": _surprise}
+    offset = start % len(HERO_TIERS)
+    for tier in HERO_TIERS[offset:] + HERO_TIERS[:offset]:
+        card = tiers[tier]()
+        if card is not None:
+            return {"tier": tier, "card": card}
 
     return None

backend/app/discover/queries.py

@@ -275,12 +275,21 @@ def plex_surprise(db: Session, uid: int, budget: str, seed: int, limit: int) ->
     return [movie_card(it, states.get(it.id)) for it in items]
 
 
+# Watch states that take an episode out of the running for "what would play next".
+_DONE = ("watched", "hidden")
+
+
 def next_episode(db: Session, uid: int, show_id: int) -> dict | None:
     """What "put that show on" means: the episode in progress, else the first unwatched one, else the
     first — in broadcast order, the same `(season, episode)` ordering `detail.py::_episode_nav` uses.
 
+    Three ordered `LIMIT 1` probes rather than one scan picked apart in Python. The Python version
+    loaded EVERY episode of the show to choose one of them — 236 rows for Friends, 227 for JAG — which
+    the comfort shelf could just about afford (a handful of hand-picked pins) and the resume rail
+    could not, since it resolves a show per rail row on the landing page.
+
     Returned as a `leaf_card` so it carries the show title the episode row itself does not."""
-    rows = db.execute(
+    base = (
         select(PlexItem, PlexState)
         .outerjoin(PlexState, and_(PlexState.item_id == PlexItem.id, PlexState.user_id == uid))
         .where(PlexItem.show_id == show_id, PlexItem.kind == "episode")
@@ -288,20 +297,26 @@ def next_episode(db: Session, uid: int, show_id: int) -> dict | None:
             PlexItem.season_number.asc().nullsfirst(),
             PlexItem.episode_number.asc().nullsfirst(),
         )
-    ).all()
-    if not rows:
+        .limit(1)
+    )
+    # In progress. `position_seconds > 0` already requires the state row to exist, so no null guard.
+    pick = db.execute(
+        base.where(PlexState.position_seconds > 0, PlexState.status.notin_(_DONE))
+    ).first()
+    # Unwatched — INCLUDING an episode with no state row at all, which is the common case and the one
+    # a bare `status NOT IN (...)` silently drops (NULL is not false, it is unknown, so the row fails
+    # the filter).
+    pick = (
+        pick
+        or db.execute(
+            base.where(or_(PlexState.id.is_(None), PlexState.status.notin_(_DONE)))
+        ).first()
+    )
+    # Fully watched show: start it again from the top.
+    pick = pick or db.execute(base).first()
+    if pick is None:
         return None
 
-    def _started(st: PlexState | None) -> bool:
-        return bool(st and st.position_seconds > 0 and st.status not in ("watched", "hidden"))
-
-    def _unseen(st: PlexState | None) -> bool:
-        return st is None or st.status not in ("watched", "hidden")
-
-    pick = next((r for r in rows if _started(r[1])), None)
-    pick = pick or next((r for r in rows if _unseen(r[1])), None)
-    pick = pick or rows[0]
-
     ep, st = pick
     show = db.get(PlexShow, show_id)
     return leaf_card(

backend/app/discover/rails.py

@@ -13,7 +13,8 @@ from sqlalchemy.orm import Session
 from app import sysconfig
 from app.discover import cards, queries
 from app.discover.queries import RAIL_LIMIT
-from app.models import User
+from app.models import PlexShow, User
+from app.plex.lookups import by_rating_key
 
 # Sort sentinel for a row whose timestamp is missing. A plain `(ts is not None, ts)` key looks like it
 # handles NULLs and does not: two NULL rows compare equal on the flag and then compare `None < None`,
@@ -27,18 +28,49 @@ def plex_available(db: Session) -> bool:
     return sysconfig.get_bool(db, "plex_enabled")
 
 
+def playable(db: Session, uid: int, card: dict) -> dict | None:
+    """The thing that would actually START from this card — itself for anything with a runtime, and
+    for a Plex SHOW the episode that is next (in progress, else the first unwatched, else the first).
+
+    ONE function, because three surfaces need the same answer and a second implementation is how the
+    shelf and the rail came to disagree in the first place: the hero calls it to decide what it is
+    offering, `continue_watching` calls it to fill each show tile's `next`, and the comfort shelf
+    resolves the same way in `pins`. None when the show has no episodes mirrored yet.
+
+    A card that already carries a resolved `next` (a rail row) is taken at its word rather than
+    re-queried — the hero reads the rail it was handed."""
+    if not (card.get("source") == "plex" and card.get("kind") == "show"):
+        return card
+    if "next" in card:
+        return card["next"]
+    sh = by_rating_key(db, PlexShow, card["id"])
+    if sh is None:
+        return None
+    ep = queries.next_episode(db, uid, sh.id)
+    return cards.from_plex(ep) if ep else None
+
+
 def continue_watching(db: Session, user: User, limit: int = RAIL_LIMIT) -> list[dict]:
     """One resume rail across both sources, most recently progressed first.
 
-    A Plex SHOW enters as a show card (that is what the Plex rail shows too, and it is what the user
-    recognises); resolving it to an episode is the hero's job, where something actually has to play."""
+    A Plex SHOW enters as a show CARD — that is what the Plex rail shows, and it is the artwork the
+    user recognises — but it carries `next`: the episode that would actually start. Without it a
+    click on a half-watched series landed on the show page with six seasons to choose between, which
+    is the decision this whole surface exists to remove (the comfort shelf and the hero already
+    resolved; only this rail did not). The client plays `next ?? card`, so the tile stays a poster and
+    the click stays one click."""
     rows: list[tuple[object, dict]] = [
         (ts, cards.from_video(r)) for ts, r in queries.yt_in_progress(db, user, limit)
     ]
     if plex_available(db):
         rows += [(ts, cards.from_plex(c)) for ts, c in queries.plex_in_progress(db, user.id, limit)]
     rows.sort(key=lambda r: r[0] or _NO_TS, reverse=True)
-    return [card for _, card in rows[:limit]]
+    out = [card for _, card in rows[:limit]]
+    # Resolve AFTER the slice: only the rows that survive it are worth a query.
+    for card in out:
+        if card["kind"] == "show":
+            card["next"] = playable(db, user.id, card)
+    return out
 
 
 def surprise(db: Session, user: User, budget: str, seed: int, limit: int = 3) -> list[dict]:

backend/app/routes/discover.py

@@ -70,6 +70,7 @@ def get_pick(
     budget: Budget = DEFAULT_BUDGET,
     seed: int = 0,
     exclude: str = "",
+    start: int = 0,
     user: User = Depends(current_user),
     db: Session = Depends(get_db),
 ) -> dict:
@@ -80,11 +81,17 @@ def get_pick(
 
     `exclude` is a comma-separated list of `<source>:<id>` keys the user has already been shown. It
     is what makes the button honest: a seed alone only moves the surprise tier, so a user with
-    something half-finished got the same card back every press."""
+    something half-finished got the same card back every press.
+
+    `start` is the press count: it rotates which tier answers first, so consecutive presses offer a
+    different KIND of answer instead of walking down the resume rail. Taken modulo the tier count in
+    `hero.pick`, so any integer is valid and no value can 422 a button."""
     skip = {p for p in exclude.split(",") if p}
     return {
         "budget": budget,
-        "hero": hero_mod.pick(db, user, budget, seed, exclude=set(list(skip)[:MAX_EXCLUDE])),
+        "hero": hero_mod.pick(
+            db, user, budget, seed, exclude=set(list(skip)[:MAX_EXCLUDE]), start=start
+        ),
     }
 
 

backend/tests/test_discover.py

@@ -388,6 +388,37 @@ def test_the_reroll_must_be_able_to_move_past_the_resume_tier(db):
     assert second["card"]["id"] == "vshort"
 
 
+def test_the_reroll_rotates_which_tier_answers(db):
+    """Measured 2026-09-06: exclusion alone left the button walking down the resume rail (20 rows)
+    and cycling nine cards, every one of them `resume` — the shelf and the surprise tier were
+    unreachable by pressing it. `start` is the press count, so consecutive presses offer a different
+    KIND of answer."""
+    user, _ = _seed_yt(db)
+    # One of each: something half-finished, something pinned, and a third video for the draw.
+    db.add(
+        VideoState(
+            user_id=user.id,
+            video_id="vmed",
+            status="new",
+            position_seconds=300,
+            progress_updated_at=NOW,
+        )
+    )
+    db.add(ComfortPin(user_id=user.id, video_id="vlong", position=0))
+    db.commit()
+    tiers = [hero.pick(db, user, "any", seed=1, start=n)["tier"] for n in range(4)]
+    assert tiers == ["resume", "comfort", "surprise", "resume"]
+
+
+def test_the_rotation_still_falls_through_an_empty_tier(db):
+    """A press must not come back empty just because the tier it happened to lead with has nothing.
+    Here there is no shelf at all, so the comfort-led press has to answer from somewhere else."""
+    user, _ = _seed_yt(db)
+    assert db.execute(select(func.count()).select_from(ComfortPin)).scalar_one() == 0
+    got = hero.pick(db, user, "any", seed=1, start=1)
+    assert got is not None and got["tier"] != "comfort"
+
+
 def test_excluding_a_show_also_excludes_the_episode_it_resolves_to(db):
     """The user rerolled past the SHOW they were shown; handing back its next episode under a
     different title would be the same suggestion wearing a hat."""
@@ -491,6 +522,67 @@ def test_a_self_playing_pin_does_not_reference_itself(db):
     assert "next" not in card["next"]
 
 
+def test_the_resume_rail_says_what_would_actually_play(db):
+    """A show tile that only opens the show page moves the decision instead of removing it — the
+    click lands on six seasons to choose between, which is the paralysis this whole surface exists
+    for. The shelf and the hero already resolved; this rail did not (reported 2026-09-06). The tile
+    stays the show (its artwork is what the user recognises); `next` is what starts."""
+    user, _ = _seed_yt(db)
+    _, show, ep1 = _seed_plex(db, user)
+    _enable_plex(db)
+    db.add(
+        PlexState(
+            user_id=user.id,
+            item_id=ep1.id,
+            status="watched",
+            watched_at=NOW,
+            progress_updated_at=NOW,
+        )
+    )
+    db.commit()
+    rail = rails.continue_watching(db, user)
+    tile = next(c for c in rail if c["kind"] == "show")
+    assert tile["id"] == "ps1"  # still the show
+    assert tile["next"]["kind"] == "episode"
+    assert tile["next"]["id"] == "ps1e2"  # ep1 is finished → ep2 is what plays
+
+
+def test_only_a_show_row_pays_for_a_resolution(db):
+    """`next` is the answer to "a show has no Play button". Attaching it to a movie or a video would
+    both cost a query for nothing and re-open the self-reference cycle the shelf already hit."""
+    user, _ = _seed_yt(db)
+    _seed_plex(db, user)
+    _enable_plex(db)
+    for card in rails.continue_watching(db, user):
+        assert ("next" in card) == (card["kind"] == "show"), card["id"]
+
+
+def test_next_episode_takes_an_episode_with_no_state_row_at_all(db):
+    """The NULL trap in the SQL rewrite: `status NOT IN ('watched','hidden')` is UNKNOWN — not true —
+    for an episode the user has never touched, so a bare filter drops exactly the common case and the
+    rail would offer episode 1 of a show already half-watched."""
+    user, _ = _seed_yt(db)
+    _, show, ep1 = _seed_plex(db, user)
+    db.add(PlexState(user_id=user.id, item_id=ep1.id, status="watched", watched_at=NOW))
+    db.commit()  # ep2 has NO PlexState row
+    assert queries.next_episode(db, user.id, show.id)["id"] == "ps1e2"
+
+
+def test_a_finished_show_starts_again_from_the_top(db):
+    """Nothing unwatched left is not "nothing to play" — it is "watch it again"."""
+    user, _ = _seed_yt(db)
+    _, show, ep1 = _seed_plex(db, user)
+    ep2 = db.execute(select(PlexItem).where(PlexItem.rating_key == "ps1e2")).scalar_one()
+    db.add_all(
+        [
+            PlexState(user_id=user.id, item_id=ep1.id, status="watched", watched_at=NOW),
+            PlexState(user_id=user.id, item_id=ep2.id, status="watched", watched_at=NOW),
+        ]
+    )
+    db.commit()
+    assert queries.next_episode(db, user.id, show.id)["id"] == "ps1e1"
+
+
 def test_next_episode_prefers_the_one_in_progress(db):
     """In progress beats "next unwatched": resuming is cheaper than starting."""
     user, _ = _seed_yt(db)

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

@@ -51,9 +51,16 @@ vi.mock("../lib/api", () => ({
   discoverCardKey: (c: { source: string; id: string }) => `${c.source}:${c.id}`,
 }));
 
-// The page hands Plex playback off to the Plex module; neither provider is under test here.
-vi.mock("./NavigationProvider", () => ({ useNavigationActions: () => ({ setPage: vi.fn() }) }));
-vi.mock("./PlexProvider", () => ({ usePlexActions: () => ({ setJumpTo: vi.fn() }) }));
+// The page hands Plex playback off to the Plex module. The provider itself is not under test, but
+// WHAT is handed over is: the jump target decides both what plays and where Back goes.
+const setPage = vi.fn();
+const setJumpTo = vi.fn();
+vi.mock("./NavigationProvider", () => ({
+  useNavigationActions: () => ({ setPage: (p: string) => setPage(p) }),
+}));
+vi.mock("./PlexProvider", () => ({
+  usePlexActions: () => ({ setJumpTo: (t: unknown) => setJumpTo(t) }),
+}));
 
 import Home from "./Home";
 
@@ -93,6 +100,39 @@ function ytCard(id: string, title: string, extra: Record<string, unknown> = {})
   };
 }
 
+/** A Plex SHOW row of the resume rail, carrying the episode that would actually start — what the
+ *  backend now attaches (`rails.continue_watching`). */
+const showCard = () => ({
+  source: "plex",
+  kind: "show",
+  id: "show-1",
+  title: "A Show",
+  subtitle: null,
+  thumb: null,
+  aspect: "poster",
+  duration_seconds: null,
+  position_seconds: 0,
+  remaining_seconds: null,
+  status: "in_progress",
+  video: null,
+  plex: { id: "show-1", type: "show", title: "A Show", thumb: "" },
+  next: {
+    source: "plex",
+    kind: "episode",
+    id: "ep-7",
+    title: "Ep 7",
+    subtitle: "A Show",
+    thumb: null,
+    aspect: "wide",
+    duration_seconds: 1500,
+    position_seconds: 0,
+    remaining_seconds: 1500,
+    status: "new",
+    video: null,
+    plex: { id: "ep-7", type: "episode", title: "Ep 7", thumb: "" },
+  },
+});
+
 const payload = (heroId: string, tier = "resume") => ({
   budget: "any",
   hero: { tier, card: ytCard(heroId, `Hero ${heroId}`) },
@@ -112,6 +152,8 @@ function mount() {
 beforeEach(() => {
   discover.mockReset();
   discoverPick.mockReset();
+  setPage.mockReset();
+  setJumpTo.mockReset();
   discover.mockResolvedValue(payload("v1"));
 });
 afterEach(cleanup);
@@ -160,7 +202,7 @@ describe("Home", () => {
     await screen.findByText("Hero v1");
     fireEvent.click(screen.getByText("home.hero.reroll"));
     await waitFor(() =>
-      expect(discoverPick).toHaveBeenCalledWith("any", expect.any(Number), ["youtube:v1"]),
+      expect(discoverPick).toHaveBeenCalledWith("any", expect.any(Number), ["youtube:v1"], 1),
     );
     expect(await screen.findByText("Rerolled")).toBeTruthy();
   });
@@ -181,4 +223,60 @@ describe("Home", () => {
     mount();
     expect(await screen.findByText("home.comfort.empty")).toBeTruthy();
   });
+
+  it("plays a half-watched SHOW's next episode instead of opening the show page", async () => {
+    // Reported 2026-09-06. A show tile that opens the show page hands back the very decision this
+    // surface exists to remove — six seasons to choose between. The rail row carries `next`, and the
+    // click follows it.
+    discover.mockResolvedValue({
+      budget: "any",
+      hero: null,
+      continue_watching: [showCard()],
+      comfort: [],
+    });
+    mount();
+    fireEvent.click(await screen.findByText("A Show"));
+    expect(setJumpTo).toHaveBeenCalledWith(expect.objectContaining({ id: "ep-7", type: "play" }));
+  });
+
+  it("hands off with `replace` so Back returns HERE, not to the Plex module's root", async () => {
+    // The hand-off is a continuation of the navigation that just pushed the Plex page entry, not a
+    // second step on top of it — without this, Back landed on the Plex Discover page the user never
+    // visited (and, under StrictMode, did nothing at all the first press).
+    discover.mockResolvedValue({
+      budget: "any",
+      hero: null,
+      continue_watching: [showCard()],
+      comfort: [],
+    });
+    mount();
+    fireEvent.click(await screen.findByText("A Show"));
+    expect(setJumpTo).toHaveBeenCalledWith(expect.objectContaining({ replace: true }));
+    expect(setPage).toHaveBeenCalledWith("plex");
+  });
+
+  it("rotates the tier on each press so the button offers a different KIND of answer", async () => {
+    // Measured 2026-09-06: exclusion alone left it walking the resume rail and cycling nine cards,
+    // never once reaching the shelf. The press count travels to the server as the rotation.
+    discoverPick.mockResolvedValue({
+      budget: "any",
+      hero: { tier: "comfort", card: ytCard("v9", "Rerolled") },
+    });
+    mount();
+    await screen.findByText("Hero v1");
+    fireEvent.click(screen.getByText("home.hero.reroll"));
+    await waitFor(() =>
+      expect(discoverPick).toHaveBeenLastCalledWith("any", expect.any(Number), ["youtube:v1"], 1),
+    );
+    await screen.findByText("Rerolled");
+    fireEvent.click(screen.getByText("home.hero.reroll"));
+    await waitFor(() =>
+      expect(discoverPick).toHaveBeenLastCalledWith(
+        "any",
+        expect.any(Number),
+        expect.any(Array),
+        2,
+      ),
+    );
+  });
 });

frontend/src/components/Home.tsx

@@ -61,9 +61,12 @@ const BUDGETS: readonly DiscoverBudget[] = ["short", "medium", "long", "any"];
 // drift from it.
 const YT_SLOT = 200;
 
-// How many already-offered cards the reroll remembers. Matched by the server's own draw depth
-// (`hero.SURPRISE_DRAW`), which has to be able to step past a full window.
-const SEEN_WINDOW = 8;
+// How many already-offered cards the reroll remembers. Matched to the server's own cap
+// (`routes/discover.MAX_EXCLUDE`) rather than to a smaller number of our own: at 8 the window rolled
+// before the resume rail (20 rows) was exhausted, so the button cycled the same nine cards forever
+// (measured, 2026-09-06). It is bounded at all only because the server will not scan an unbounded
+// exclusion list.
+const SEEN_WINDOW = 32;
 
 // The four shelf moves, in the order they appear in the menu.
 const SHELF_MOVES: readonly [ShelfMove, string, typeof ChevronLeft][] = [
@@ -337,6 +340,10 @@ export default function Home() {
   // 0 = "the hero the page loaded with". Any other value is a reroll, answered by its own query so
   // pressing the button does not refetch the rails under the user's cursor.
   const [seed, setSeed] = useState(0);
+  // Which press this is. It rotates the tier the server leads with, so "Mást kérek" offers a
+  // different KIND of answer each time (where you left off → your shelf → a surprise) rather than
+  // the next row of the same rail. Reset with the budget: a new question starts the rotation over.
+  const [press, setPress] = useState(0);
   // The cards the reroll has already offered this session, newest last. A ROLLING window rather than
   // the whole history: an unbounded list would eventually exclude everything and leave the button
   // with nothing to give, whereas a window of 8 can never exhaust a library and only repeats after
@@ -353,8 +360,8 @@ export default function Home() {
     placeholderData: keepPreviousData,
   });
   const pickQ = useQuery({
-    queryKey: qk.discoverPick(budget, seed, seen),
-    queryFn: () => api.discoverPick(budget, seed, seen),
+    queryKey: qk.discoverPick(budget, seed, seen, press),
+    queryFn: () => api.discoverPick(budget, seed, seen, press),
     enabled: seed !== 0,
     staleTime: 0,
     // Hold the previous hero while the next one is in flight. Without this the reroll's new query key
@@ -415,7 +422,14 @@ export default function Home() {
         return;
       }
       if (target.plex) {
-        setJumpTo({ id: target.plex.id, type: target.plex.type === "show" ? "show" : "play" });
+        // `replace`: the Plex module's sub-view rewrites the page entry `setPage` is about to push,
+        // so browser-Back from the player returns HERE — not to the Plex Discover root, which this
+        // navigation passed through and the user never saw.
+        setJumpTo({
+          id: target.plex.id,
+          type: target.plex.type === "show" ? "show" : "play",
+          replace: true,
+        });
         setPage("plex");
       }
     },
@@ -427,7 +441,11 @@ export default function Home() {
   const onInfo = useCallback(
     (card: DiscoverCard) => {
       if (!card.plex) return;
-      setJumpTo({ id: card.plex.id, type: card.plex.type === "show" ? "show" : "movie" });
+      setJumpTo({
+        id: card.plex.id,
+        type: card.plex.type === "show" ? "show" : "movie",
+        replace: true,
+      });
       setPage("plex");
     },
     [setJumpTo, setPage],
@@ -485,6 +503,7 @@ export default function Home() {
     // would look like a dead button).
     if (heroKey)
       setSeen((prev) => [...prev.filter((k) => k !== heroKey), heroKey].slice(-SEEN_WINDOW));
+    setPress((n) => n + 1);
     setSeed((prev) => {
       let next = prev;
       while (next === prev || next === 0) next = Math.floor(Math.random() * 1_000_000) + 1;
@@ -515,6 +534,7 @@ export default function Home() {
             setBudget(v);
             setSeed(0); // the payload for the new budget carries its own hero
             setSeen([]); // a new question deserves the whole library again
+            setPress(0); // …and the tier rotation starts from the page's own priority order
           }}
           options={BUDGETS.map((b) => ({ value: b, label: t(`home.budget.${b}`) }))}
         />

frontend/src/components/PlexBrowse.tsx

@@ -141,6 +141,11 @@ export default function PlexBrowse() {
           : jumpTo.type === "play"
             ? { kind: "player", id: jumpTo.id }
             : { kind: "info", id: jumpTo.id },
+        // A cross-module hand-off continues the navigation that brought us here rather than adding
+        // to it. It also makes this effect idempotent, which matters more than it looks: under
+        // StrictMode the effect body runs twice before `setJumpTo(null)` re-renders, and two pushes
+        // of the SAME sub-view left a duplicate entry whose Back visibly did nothing.
+        { replace: jumpTo.replace },
       );
       setJumpTo(null);
     }

frontend/src/components/PlexProvider.tsx

@@ -33,7 +33,17 @@ import { useNavigation } from "./NavigationProvider";
 // single Play button — the PLAYER for a movie/episode rating_key. `play` exists because the player
 // lives inside this module with its lazy hls.js and its provider tree; mounting a second one on the
 // landing page to avoid one hand-off would be the expensive way round.
-export type PlexJumpTarget = { id: string; type: "movie" | "show" | "play" };
+export type PlexJumpTarget = {
+  id: string;
+  type: "movie" | "show" | "play";
+  /** The jump ARRIVED WITH a page change — another module set this and sent the user here in one
+   *  gesture (the Home surface plays a Plex title). The opened sub-view then REPLACES the page entry
+   *  that hand-off just pushed, instead of stacking on top of it, so Back returns to where the user
+   *  actually came from rather than to a module root they never visited. Omitted for a jump made
+   *  from INSIDE the Plex module (the header typeahead), where the entry being replaced would be a
+   *  sub-view the user really was looking at. */
+  replace?: boolean;
+};
 
 type PlexState = {
   scope: string; // movie | show | both (unified cross-library scope)

frontend/src/lib/api/discover.dom.test.ts

@@ -0,0 +1,52 @@
+// @vitest-environment jsdom
+//
+// The Home surface's slice builds its own query strings, and the Home DOM tests mock this module —
+// so nothing else in the suite ever looks at the URL that actually goes out. That gap hid a live
+// parameter once already: the reroll's `start` reached `api.discoverPick` and stopped there.
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import { discoverApi } from "./discover";
+
+const fetchMock = vi.fn();
+
+beforeEach(() => {
+  fetchMock.mockReset().mockResolvedValue({
+    ok: true,
+    status: 200,
+    headers: new Headers({ "content-type": "application/json" }),
+    json: async () => ({}),
+    text: async () => "{}",
+  });
+  vi.stubGlobal("fetch", fetchMock);
+});
+afterEach(() => vi.unstubAllGlobals());
+
+// Indexed, not `.at(-1)`: the e2e tsconfig's lib target predates it, and the gate typechecks three
+// projects.
+const lastUrl = (): string => {
+  const calls = fetchMock.mock.calls;
+  return String(calls[calls.length - 1]?.[0]);
+};
+
+describe("discoverApi query strings", () => {
+  it("sends the press count as `start` — the tier rotation lives on the wire", async () => {
+    await discoverApi.discoverPick("medium", 42, [], 3);
+    expect(lastUrl()).toContain("start=3");
+    expect(lastUrl()).toContain("budget=medium");
+    expect(lastUrl()).toContain("seed=42");
+  });
+
+  it("sends the press count even on the first press, so `start` is never implied", async () => {
+    await discoverApi.discoverPick("any", 7);
+    expect(lastUrl()).toContain("start=0");
+  });
+
+  it("encodes the exclusion list, whose keys carry a colon", async () => {
+    await discoverApi.discoverPick("any", 1, ["youtube:abc", "plex:99"], 2);
+    expect(lastUrl()).toContain(`exclude=${encodeURIComponent("youtube:abc,plex:99")}`);
+  });
+
+  it("omits `exclude` entirely when there is nothing to exclude", async () => {
+    await discoverApi.discoverPick("any", 1, [], 0);
+    expect(lastUrl()).not.toContain("exclude=");
+  });
+});

frontend/src/lib/api/discover.ts

@@ -70,13 +70,16 @@ export const discoverApi = {
   // user's cursor.
   // `exclude` is the rolling list of `<source>:<id>` keys already shown. Without it a reroll only
   // moves the surprise tier, so a user with something half-finished gets the same hero back.
+  // `press` is which press this is; it rotates the tier the server answers from, so consecutive
+  // presses offer a different KIND of answer instead of walking down the resume rail.
   discoverPick: (
     budget: DiscoverBudget,
     seed: number,
     exclude: string[] = [],
+    press = 0,
   ): Promise<{ budget: DiscoverBudget; hero: DiscoverHero | null }> =>
     req(
-      `/api/discover/pick?budget=${budget}&seed=${seed}` +
+      `/api/discover/pick?budget=${budget}&seed=${seed}&start=${press}` +
         (exclude.length ? `&exclude=${encodeURIComponent(exclude.join(","))}` : ""),
     ),
   comfortPins: (): Promise<{ items: DiscoverCard[] }> => req("/api/discover/pins"),

frontend/src/lib/history.subview.dom.test.ts

@@ -76,6 +76,42 @@ describe("useHistorySubview open", () => {
     expect(window.history.state?._sub).toBe("root");
     expect(window.location.search).toBe(""); // ?v dropped
   });
+
+  // E24: a cross-module hand-off (Home plays a Plex title) arrives on an entry the page navigation
+  // just pushed. Opening the sub-view on TOP of it stranded the user on a module root they never
+  // visited — browser-Back from the player landed on the Plex Discover page instead of Home
+  // (measured 2026-09-06). `replace` makes the sub-view BE that entry.
+  it("replace rewrites the current entry instead of stacking a new one", () => {
+    const before = window.history.length;
+    const { result } = renderHook(() => useHistorySubview("root", url));
+    act(() => result.current.open("a", { replace: true }));
+    expect(result.current.view).toBe("a");
+    expect(window.history.state?._sub).toBe("a");
+    expect(window.location.search).toBe("?v=a");
+    expect(window.history.length).toBe(before); // no new entry to Back through
+  });
+
+  it("replace is idempotent — two opens of the same view are still one entry", () => {
+    // Not a nicety: under StrictMode the jumpTo effect body runs TWICE before its `setJumpTo(null)`
+    // re-renders, and two pushes of the identical sub-view left a duplicate whose Back visibly did
+    // nothing.
+    const before = window.history.length;
+    const { result } = renderHook(() => useHistorySubview("root", url));
+    act(() => {
+      result.current.open("a", { replace: true });
+      result.current.open("a", { replace: true });
+    });
+    expect(window.history.length).toBe(before);
+  });
+
+  it("keeps the entry's own sfScroll id on a replace", () => {
+    // It is the SAME entry, so it keeps its scroll identity; PageScroller keys offsets per
+    // (entry, view), and the view key changed, so the sub-view still opens at the top.
+    setUrl("/", { sfScroll: 7 });
+    const { result } = renderHook(() => useHistorySubview("root", url));
+    act(() => result.current.open("a", { replace: true }));
+    expect(window.history.state?.sfScroll).toBe(7);
+  });
 });
 
 describe("useHistorySubview popstate", () => {

frontend/src/lib/history.ts

@@ -81,7 +81,10 @@ export function useHistorySubview<T>(
   url?: SubviewUrl<T>,
 ): {
   view: T;
-  open: (next: T) => void;
+  /** `replace` rewrites the CURRENT entry instead of stacking a new one — for a sub-view that is the
+   *  continuation of the navigation that just arrived here, not a step the user took inside the
+   *  module. See the `jumpTo` hand-off in PlexBrowse. */
+  open: (next: T, opts?: { replace?: boolean }) => void;
   back: () => void;
 } {
   // Resolve the current entry's sub-view: history.state._sub for an in-app entry, else decode the
@@ -110,9 +113,17 @@ export function useHistorySubview<T>(
   }, []);
   return {
     view,
-    open: (next: T) => {
+    open: (next: T, opts?: { replace?: boolean }) => {
       setView(next);
       const href = url ? urlWithParams({ [url.key]: url.encode(next) }) : "";
+      if (opts?.replace) {
+        // Same ENTRY, so it keeps its sfScroll id: PageScroller keys offsets per (entry, view), and
+        // the view key has changed, so the sub-view still opens at the top without minting an id
+        // that would orphan the one this entry already carries.
+        window.history.replaceState({ ...window.history.state, _sub: next }, "", href);
+        notifyNav();
+        return;
+      }
       // A fresh sfScroll so the opened sub-view is its own scroll entry (starts at the top, and Back
       // restores the view we came from) — then notify PageScroller, which this push doesn't re-render.
       window.history.pushState(