feat(feed): signature-aware volatile merge with date-banded fetch-more

2026-08-13 17:46:27 -04:00
parent 42c48e59fb
commit 878d1e01ab
9 changed files with 406 additions and 57 deletions
--- a/src/pages/Settings/PreferencesPanel.tsx
+++ b/src/pages/Settings/PreferencesPanel.tsx
@@ -221,7 +221,7 @@ export function usePreferencesItems(): SettingItem[] {
 			kind: "select",
 			display: () => cacheModeLabel(prefs().episodeCacheMode),
 			help: () =>
-				`How the Feed and My Shows episode lists are bounded.\nDate: keep episodes from the last N days (see Cache Days below); Fetch More reveals the next 2 weeks per press.\nCount: keep the N most recent episodes (see Cache Count below); Fetch More pages in 50-episode chunks.\nFetch More always pages beyond this bound — these episodes are volatile and don't persist.\nType: select\nDefault: date\nCurrent: ${cacheModeLabel(prefs().episodeCacheMode)}\nCycle with j/k; Enter to apply.`,
+				`How the Feed and My Shows episode lists are bounded.\nDate: keep episodes from the last N days (see Cache Days below); Fetch More reveals the next 2 weeks per press.\nCount: the Feed list is the N most-recent episodes across ALL shows (not N per show); Fetch More reveals N more of the newest episodes each press — deep history only appears once you page to it.\nFetch More always pages beyond this bound — these episodes are volatile and don't persist.\nType: select\nDefault: date\nCurrent: ${cacheModeLabel(prefs().episodeCacheMode)}\nCycle with j/k; Enter to apply.`,
 			cycle: (dir) => {
 				const idx = CACHE_MODE_LABELS.findIndex(
 					(s) => s.value === prefs().episodeCacheMode,
--- a/src/stores/feed.ts
+++ b/src/stores/feed.ts
@@ -13,8 +13,12 @@ import { DEFAULT_SOURCES } from "../types/source";
 import { getRSSItems, parseRSSItem, parseChannelCoverUrl } from "../api/rss-parser";
 import { resolveItunesFeedUrl } from "../utils/itunes-feed-resolver";
 import { savePodcastIndexCredentials } from "../utils/source-credentials";
-import { mergeEpisodesBounded } from "../utils/episode-merge";
 import {
+	episodeSignature,
+	mergeEpisodesBounded,
+} from "../utils/episode-merge";
+import {
+	DEFAULT_EPISODE_WINDOW_DAYS,
 	episodeInWindow,
 	loadFeedsFromFile,
 	saveFeedsToFile,
@@ -139,6 +143,31 @@ const epTs = (ep: Episode): number => {
 	return t === undefined || Number.isNaN(t) ? Infinity : t;
 };

+/** Date-mode fetch-more cutoff: the oldest loaded episode's pubDate minus the
+ *  2-week band. With nothing loaded (a show whose episodes all fall outside
+ *  the cache window), the band anchors at the cache-window edge (now minus
+ *  the configured days) — a dormant show can't drag in arbitrarily old
+ *  episodes just because the button is pressed. */
+const dateFetchMoreCutoff = (
+	cached: Episode[],
+	loaded: number,
+	windowDays: number,
+): number => {
+	if (loaded > 0) {
+		const t = epTs(cached[loaded - 1]);
+		if (Number.isFinite(t)) {
+			return t - FETCH_MORE_WINDOW_DAYS * 24 * 3600 * 1000;
+		}
+	}
+	// Nothing loaded: the band extends FETCH_MORE_WINDOW_DAYS before the
+	// cache-window edge (e.g. 60d → reveals the 60–74d slice).
+	return (
+		Date.now() -
+		Math.max(1, windowDays) * 24 * 3600 * 1000 -
+		FETCH_MORE_WINDOW_DAYS * 24 * 3600 * 1000
+	);
+};
+
 /** Save feeds to file (async, fire-and-forget). */
 function saveFeeds(feeds: Feed[]): void {
 	const prefs = useAppStore().state().preferences;
@@ -203,12 +232,21 @@ async function migratePlaintextCredentials(
 *  union semantics the merged list legitimately contains episodes BEYOND the
 *  fetched window, so unchanged-detection must compare the fetched window
 *  against the existing list's prefix — comparing full lists would bump
- *  `lastUpdated` on every refresh. */
-function sameRefreshWindow(existing: Episode[], fetched: Episode[]): boolean {
+ *  `lastUpdated` on every refresh. When ids drifted between refreshes (the
+ *  one-time positional-id migration, or a feed that rotates enclosure URLs)
+ *  the id sets differ for the SAME content, so a content-signature
+ *  comparison decides: an unchanged feed stays unchanged. */
+export function sameRefreshWindow(
+	existing: Episode[],
+	fetched: Episode[],
+): boolean {
 	if (fetched.length === 0) return true;
 	const prefix = existing.slice(0, fetched.length);
 	const ids = new Set(prefix.map((e) => e.id));
-	return fetched.every((e) => ids.has(e.id));
+	if (fetched.every((e) => ids.has(e.id))) return true;
+	if (prefix.length !== fetched.length) return false;
+	const signatures = new Set(prefix.map(episodeSignature));
+	return fetched.every((e) => signatures.has(episodeSignature(e)));
 }

 /** Run `fn` over every item with at most `limit` executions in flight — a
@@ -249,6 +287,11 @@ function createFeedStore() {
 	const [selectedFeedId, setSelectedFeedId] = createSignal<string | null>(null);
 	const [isLoadingMore, setIsLoadingMore] = createSignal(false);
 	const [isLoadingFeeds, setIsLoadingFeeds] = createSignal(false);
+	/** Feed-page fetch-more presses in COUNT mode: the global list is capped
+	 *  at episodeCacheCount × (presses + 1) episodes, so one press reveals
+	 *  exactly N more of the NEWEST episodes across all shows — it can never
+	 *  dump deep history (see getAllEpisodesChronological). */
+	const [countFetchMorePresses, setCountFetchMorePresses] = createSignal(0);

 	// ── Debounced persistence ───────────────────────────────────────────────
 	/** Trailing-edge debounce window for config.json writes. */
@@ -357,6 +400,20 @@ function createFeedStore() {
 			(a, b) => b.episode.pubDate.getTime() - a.episode.pubDate.getTime(),
 		);

+		// COUNT mode: the Feed page is a GLOBAL top-K list — the newest
+		// `episodeCacheCount × (fetch-more presses + 1)` episodes across ALL
+		// shows, not N per show. A press reveals exactly N more recent
+		// episodes; deep history never surfaces in one jump. The cap stays
+		// even once every cache is exhausted (the button hides) — lifting it
+		// rendered the full deep union and froze the UI.
+		const prefs = useAppStore().state().preferences;
+		if (prefs.episodeCacheMode === "count") {
+			const limit =
+				Math.max(1, prefs.episodeCacheCount ?? 25) *
+				(countFetchMorePresses() + 1);
+			return allEpisodes.slice(0, limit);
+		}
+
 		return allEpisodes;
 	};

@@ -814,15 +871,25 @@ function createFeedStore() {

 	/** Check if a feed has more episodes available beyond what's currently
 	 *  loaded. The full parse cache holds ALL episodes (including beyond the
-	 *  cache bound), so fetch-more can always page deeper — the bound limits
-	 *  what the Feed/My Shows list shows initially, not what fetch-more can
-	 *  reach. When the loaded window reaches the cache length, this flips
-	 *  false. */
+	 *  cache bound), so fetch-more can page deeper — but in DATE mode only
+	 *  when the next unloaded episode falls inside the next 2-week band: a
+	 *  sparse/dormant show whose band is empty reports false, so fetch-more
+	 *  never drags in arbitrarily old episodes just because the parse cache
+	 *  holds them. When the loaded window reaches the cache length (or the
+	 *  band is empty), this flips false. */
 	const hasMoreEpisodes = (feedId: string): boolean => {
 		const cached = fullEpisodeCache.get(feedId);
 		if (!cached) return false;
 		const loaded = episodeLoadCount.get(feedId) ?? 0;
-		return loaded < cached.length;
+		if (loaded >= cached.length) return false;
+		const prefs = useAppStore().state().preferences;
+		if (prefs.episodeCacheMode === "count") return true;
+		const cutoff = dateFetchMoreCutoff(
+			cached,
+			loaded,
+			prefs.episodeCacheDays ?? DEFAULT_EPISODE_WINDOW_DAYS,
+		);
+		return epTs(cached[loaded]) >= cutoff;
 	};

 	/** Load the next chunk of episodes for one feed from the full parse
@@ -879,15 +946,19 @@ function createFeedStore() {
 		const prefs = useAppStore().state().preferences;

 		// Date mode: each press reveals the next FETCH_MORE_WINDOW_DAYS band
-		// past the oldest loaded episode — a daily show gains ~2 weeks of
-		// episodes, a weekly show gains its next 2, never a fixed count.
+		// past the oldest loaded episode (or the cache-window edge when
+		// nothing is loaded) — a daily show gains ~2 weeks of episodes, a
+		// weekly show gains its next 2, never a fixed count. An empty band
+		// is a genuine stop (hasMoreEpisodes hides the button) — no minimum,
+		// so a sparse/dormant show can't grab arbitrarily old episodes.
 		// Count mode keeps the fixed MAX_EPISODES_REFRESH chunk.
 		let newCount: number;
 		if (prefs.episodeCacheMode === "date") {
-			const ref = cached[Math.max(0, currentCount - 1)];
-			const refTs = ref ? epTs(ref) : Infinity;
-			if (Number.isFinite(refTs)) {
-				const cutoff = refTs - FETCH_MORE_WINDOW_DAYS * 24 * 3600 * 1000;
+			const cutoff = dateFetchMoreCutoff(
+				cached,
+				currentCount,
+				prefs.episodeCacheDays ?? DEFAULT_EPISODE_WINDOW_DAYS,
+			);
 			newCount = currentCount;
 			while (
 				newCount < cached.length &&
@@ -895,13 +966,6 @@ function createFeedStore() {
 			) {
 				newCount++;
 			}
-			} else {
-				newCount = currentCount;
-			}
-			// Date mode always advances at least one episode: a sparse band
-			// (a show that went quiet) must not wedge the button into a
-			// no-op while hasMoreEpisodes still reports true.
-			newCount = Math.max(newCount, currentCount + 1);
 		} else {
 			newCount = currentCount + MAX_EPISODES_REFRESH;
 		}
@@ -947,15 +1011,78 @@ function createFeedStore() {
 		return feeds().some((f) => hasMoreEpisodes(f.id));
 	};

-	/** Advance the loaded window by MAX_EPISODES_REFRESH for every feed that
-	 *  still has cached episodes — powers the Feed page's "[Fetch More]". */
+	/** Power the Feed page's "[Fetch More]".
+	 *  Date mode: advance each feed's window by its 2-week band (empty bands
+	 *  — sparse/dormant shows — are skipped).
+	 *  Count mode: the global list cap grows by one count (see
+	 *  getAllEpisodesChronological) and every feed's window deepens by one
+	 *  count so the growing cap has material; one press reveals exactly N
+	 *  more RECENT episodes, never a far-back dump.
+	 *  Both modes compute every feed's new window FIRST (yielding between
+	 *  feeds so the renderer keeps painting) and apply ONE setFeeds — the
+	 *  Feed list rebuilds once per press instead of once per feed (the
+	 *  per-feed storms froze the UI). */
 	const loadMoreAllFeeds = async () => {
 		if (isLoadingMore()) return;
 		setIsLoadingMore(true);
 		try {
-			const pending = feeds().filter((f) => hasMoreEpisodes(f.id));
-			for (const feed of pending) {
-				await loadMoreEpisodesForFeed(feed.id);
+			const prefs = useAppStore().state().preferences;
+			const count = Math.max(1, prefs.episodeCacheCount ?? 25);
+			if (prefs.episodeCacheMode === "count") {
+				setCountFetchMorePresses((p) => p + 1);
+			}
+			const windowDays =
+				prefs.episodeCacheDays ?? DEFAULT_EPISODE_WINDOW_DAYS;
+
+			const updates: Array<{ feedId: string; episodes: Episode[] }> = [];
+			for (const feed of feeds()) {
+				const cached = fullEpisodeCache.get(feed.id);
+				if (!cached) continue;
+				const currentCount =
+					episodeLoadCount.get(feed.id) ?? feed.episodes.length;
+				if (currentCount >= cached.length) continue;
+				let newCount: number;
+				if (prefs.episodeCacheMode === "count") {
+					newCount = Math.min(currentCount + count, cached.length);
+				} else {
+					// Date mode: skip feeds whose next band is empty — the
+					// button must not surface arbitrarily old episodes.
+					const cutoff = dateFetchMoreCutoff(
+						cached,
+						currentCount,
+						windowDays,
+					);
+					if (epTs(cached[currentCount]) < cutoff) continue;
+					newCount = currentCount;
+					while (
+						newCount < cached.length &&
+						epTs(cached[newCount]) >= cutoff
+					) {
+						newCount++;
+					}
+				}
+				if (newCount <= currentCount) continue;
+				episodeLoadCount.set(feed.id, newCount);
+				updates.push({
+					feedId: feed.id,
+					episodes: cached.slice(0, newCount),
+				});
+				// Yield so the renderer paints between feed computations.
+				await yieldToUI();
+			}
+
+			if (updates.length > 0) {
+				const byId = new Map(
+					updates.map((u) => [u.feedId, u.episodes]),
+				);
+				setFeeds((prev) =>
+					prev.map((f) =>
+						byId.has(f.id)
+							? { ...f, episodes: byId.get(f.id)! }
+							: f,
+					),
+				);
+				scheduleSaveFeeds();
 			}
 		} finally {
 			setIsLoadingMore(false);
@@ -990,6 +1117,11 @@ function createFeedStore() {
 		// Actions
 		setFilter,
 		setSelectedFeedId,
+		/** Fetch + parse an RSS feed WITHOUT subscribing or touching any feed
+		 *  record (Discover's episode preview). Pass no feedId to skip the
+		 *  full-parse cache; the visible window is bounded by the user's
+		 *  cache preference and `limit`. */
+		fetchEpisodes,
 		addFeed,
 		hasFeedByUrl,
 		removeFeed,
--- a/src/utils/episode-merge.ts
+++ b/src/utils/episode-merge.ts
@@ -8,11 +8,35 @@ const ts = (ep: Episode): number => {
  return t === undefined || Number.isNaN(t) ? Infinity : t
 }

+/** PubDate stamp for identity matching — undated episodes collapse to a
+ *  single token so their twins match by title alone. */
+const stamp = (ep: Episode): string => {
+  const t = ep.pubDate?.getTime()
+  return t === undefined || Number.isNaN(t) ? "undated" : String(t)
+}
+
+/**
+ * Content signature identifying the SAME episode across id changes. Episode
+ * ids are stable (guid / enclosure-URL derived), but a feed can still change
+ * an episode's id between refreshes: the one-time migration from the old
+ * positional-id scheme, or a host that rotates signed enclosure URLs. title +
+ * pubDate is the most stable combination that survives both — a feed
+ * re-issuing an episode with the same title and date IS that episode.
+ */
+export const episodeSignature = (ep: Episode): string =>
+  `${ep.title}\u0000${stamp(ep)}`
+
 /**
 * Union of two episode lists keyed by id — on collision the fetched copy
- * wins (fresh metadata). Result is sorted newest-first by pubDate and pruned
- * by the supplied `keep` predicate: episodes outside the configured cache
- * bound (date window or count) are dropped. Never mutates either input.
+ * wins (fresh metadata). An existing episode whose id differs from every
+ * fetched id but whose content signature matches a fetched episode is a
+ * stale-id twin (id migration / rotating enclosure URLs) and is dropped,
+ * otherwise the union would double every episode on the first refresh after
+ * the id scheme changed. Existing episodes with NO fetched twin survive
+ * (volatile in-memory window). Result is sorted newest-first by pubDate and
+ * pruned by the supplied `keep` predicate: episodes outside the configured
+ * cache bound (date window or count) are dropped. Never mutates either
+ * input.
 *
 * The caller supplies `keep` so this module stays free of the preference
 * types — the feed store passes a closure bound to the user's mode/count/days.
@@ -23,8 +47,17 @@ export function mergeEpisodesBounded(
  keep: (ep: Episode, index: number) => boolean,
 ): Episode[] {
  const byId = new Map<string, Episode>()
-  for (const ep of existing) byId.set(ep.id, ep)
-  for (const ep of fetched) byId.set(ep.id, ep)
-  const sorted = [...byId.values()].sort((a, b) => ts(b) - ts(a))
+  const bySignature = new Map<string, Episode>()
+  for (const ep of fetched) {
+    byId.set(ep.id, ep)
+    bySignature.set(episodeSignature(ep), ep)
+  }
+  const merged = [...byId.values()]
+  for (const ep of existing) {
+    if (byId.has(ep.id)) continue
+    if (bySignature.has(episodeSignature(ep))) continue
+    merged.push(ep)
+  }
+  const sorted = merged.sort((a, b) => ts(b) - ts(a))
  return sorted.filter((ep, i) => keep(ep, i))
 }
--- a/tasks/bounded-feed-lifecycle/02-volatile-episode-merge.md
+++ b/tasks/bounded-feed-lifecycle/02-volatile-episode-merge.md
@@ -59,6 +59,7 @@ tests:
    - Refresh-keeps-volatile-window: serve 3 episodes at t0, `addFeed`; then serve the same 3 plus 2 new ones, `refreshFeed`. Assert `feed.episodes.length === 5` AND `lastUpdated` advanced AND a second identical refresh leaves `lastUpdated` untouched (window-compare, not union-compare).
    - Boundary: a 25-day-old episode loads; a 70-day-old episode is neither visible nor cached initially, but fetch-more surfaces it (volatile).
    - Date stepping: 30 episodes at 3-day spacing — each fetch-more press reveals the next 2-week band (24 → 28 → 30), NOT a fixed 50-chunk.
+    - Count-mode global step: two feeds with staggered dates — one Feed-page press adds the configured N most-recent UNLOADED episodes across ALL shows (N total, not N per show), via the k-way frontier merge in `loadMoreAllFeedsByCount`.
    - Out-of-window never cached: 600 items at 2h spacing span ~50 days — only the in-window tail is loadable (fewer than the old 500 cap), `hasMoreEpisodes` flips false there.
    - No count ceiling: 600 items at 1h spacing (all within 25 days) are ALL loadable — the bound is the date, not a number.
  - Clock constraint: these tests run under fake timers, and a large `vi.advanceTimersByTime` (past ~5 days of fake time) makes Bun 1.3.8 hang every subsequent network fetch — the boundary is pinned with relative pubDates, never by moving the clock across it.
--- a/tests/feed-nonblocking.test.ts
+++ b/tests/feed-nonblocking.test.ts
@@ -62,7 +62,7 @@ const addedFeedIds: string[] = [];
 /** Feed created by the debounce test, reused by the flushPendingSave test. */
 let debounceFeedId = "";

-/** XML for the current served episode list (episode ids = feedUrl#index). */
+/** XML for the current served episode list (episode ids derive from enclosure URLs). */
 function feedXml(episodes: ServedEpisode[], origin: string): string {
 	const items = episodes
 		.map(
--- a/tests/feed-pagination.test.ts
+++ b/tests/feed-pagination.test.ts
@@ -42,7 +42,7 @@ let servedEpisodes: ServedEpisode[] = [];
 // store (execution order between files is not guaranteed).
 const addedFeedIds: string[] = [];

-/** XML for the current served episode list (episode ids = feedUrl#index). */
+/** XML for the current served episode list (episode ids derive from enclosure URLs). */
 function feedXml(episodes: ServedEpisode[], origin: string): string {
 	const items = episodes
 		.map(
@@ -71,7 +71,10 @@ const makePodcast = (feedUrl: string): Podcast => ({
 	isSubscribed: true,
 });

-beforeAll(() => {
+beforeAll(async () => {
+	// The app store loads its persisted prefs asynchronously at import; wait
+	// for that so our count-mode override isn't clobbered by the load.
+	await useAppStore().whenReady();
 	// Chunk-based stepping is count-mode behavior (see header comment).
 	useAppStore().updatePreferences({
 		episodeCacheMode: "count",
--- a/tests/feed-refresh.test.ts
+++ b/tests/feed-refresh.test.ts
@@ -42,7 +42,7 @@ let feedAId = "";
 /** When set, the server 503s this path — simulates a feed going down. */
 let failPath: string | null = null;

-/** XML for the current served episode list (episode ids = feedUrl#index). */
+/** XML for the current served episode list (episode ids derive from enclosure URLs). */
 function feedXml(episodes: ServedEpisode[], origin: string): string {
 	const items = episodes
 		.map(
@@ -79,6 +79,18 @@ beforeAll(() => {
 			if (failPath && url.pathname === failPath) {
 				return new Response("feed unavailable", { status: 503 });
 			}
+			// A dedicated single-episode feed for the failed-refresh test:
+			// it must not depend on (or shrink) the shared servedEpisodes
+			// list, which other tests' feeds read on refreshAllFeeds.
+			if (url.pathname === "/flaky.xml") {
+				return new Response(
+					feedXml(
+						[{ title: "Ep 1", date: "2026-08-01T00:00:00Z" }],
+						url.origin,
+					),
+					{ headers: { "Content-Type": "application/rss+xml" } },
+				);
+			}
 			if (url.pathname.endsWith(".xml")) {
 				return new Response(feedXml(servedEpisodes, url.origin), {
 					headers: { "Content-Type": "application/rss+xml" },
@@ -139,8 +151,9 @@ test("refresh with a genuinely new episode bumps lastUpdated", async () => {

 test("a failed refresh does not wipe the feed's episodes", async () => {
 	const store = useFeedStore();
-	const savedEpisodes = servedEpisodes;
-	servedEpisodes = [{ title: "Ep 1", date: "2026-08-01T00:00:00Z" }];
+	// /flaky.xml serves its own fixed single-episode feed (see server route)
+	// so the shared servedEpisodes list stays untouched for feedA, which
+	// refreshAllFeeds below also refreshes.
 	const feedUrl = `http://127.0.0.1:${server!.port}/flaky.xml`;
 	const feed = await store.addFeed(makePodcast(feedUrl), "test-source");
 	expect(feed).not.toBeNull();
@@ -161,11 +174,6 @@ test("a failed refresh does not wipe the feed's episodes", async () => {

 	failPath = null;
 	store.removeFeed(feedId);
-	// Restore the shared served content: with union merge semantics (volatile
-	// episodes survive refreshes) this feed keeps its larger in-memory window,
-	// so later tests must serve the same episodes they added — a shrink here
-	// would make the next test's "unchanged" refresh genuinely different.
-	servedEpisodes = savedEpisodes;
 });

 test("refreshAllFeeds keeps unchanged feeds' order and timestamps", async () => {
--- a/tests/feed-volatile-merge.test.ts
+++ b/tests/feed-volatile-merge.test.ts
@@ -28,7 +28,7 @@ import { join } from "path";
 const configHome = mkdtempSync(join(tmpdir(), "podtui-volatile-"));
 process.env.XDG_CONFIG_HOME = configHome;

-import { useFeedStore } from "../src/stores/feed";
+import { sameRefreshWindow, useFeedStore } from "../src/stores/feed";
 import { mergeEpisodesBounded } from "../src/utils/episode-merge";
 import { episodeInWindow } from "../src/utils/feeds-persistence";
 import { useAppStore } from "../src/stores/app";
@@ -132,6 +132,67 @@ test("mergeEpisodesBounded dedupes on id collision and keeps the fetched copy",
 	expect(merged.find((e) => e.id === "a")!.title).toBe("New Title");
 });

+test("mergeEpisodesBounded drops stale-id twins (id migration / rotating enclosure URLs)", () => {
+	// The same two episodes with different ids on both sides — exactly what a
+	// refresh sees after the positional-id → stable-id migration (or a host
+	// that rotates signed audio URLs). Without content matching the union
+	// would double every episode.
+	const d1 = new Date("2026-08-01T00:00:00Z");
+	const d2 = new Date("2026-08-02T00:00:00Z");
+	const existing = [
+		makeEpisode("feed#0", "Ep 1", d1),
+		makeEpisode("feed#1", "Ep 2", d2),
+	];
+	const fetched = [
+		makeEpisode("feed#guid:g1", "Ep 1", d1),
+		makeEpisode("feed#guid:g2", "Ep 2", d2),
+	];
+	const keepAll = () => true;
+
+	const merged = mergeEpisodesBounded(existing, fetched, keepAll);
+
+	expect(merged.map((e) => e.id)).toEqual(["feed#guid:g2", "feed#guid:g1"]);
+	expect(merged).toHaveLength(2);
+});
+
+test("mergeEpisodesBounded keeps an existing episode with no fetched twin (volatile window)", () => {
+	// Fetched covers Ep 1 only (by content twin). Ep 2 exists only in memory
+	// — the volatile window — and must survive the refresh.
+	const d1 = new Date("2026-08-01T00:00:00Z");
+	const d2 = new Date("2026-08-02T00:00:00Z");
+	const existing = [
+		makeEpisode("feed#0", "Ep 1", d1),
+		makeEpisode("feed#1", "Ep 2", d2),
+	];
+	const fetched = [makeEpisode("feed#guid:g1", "Ep 1", d1)];
+	const keepAll = () => true;
+
+	const merged = mergeEpisodesBounded(existing, fetched, keepAll);
+
+	expect(merged).toHaveLength(2);
+	expect(merged.map((e) => e.title).sort()).toEqual(["Ep 1", "Ep 2"]);
+});
+
+test("sameRefreshWindow treats id drift with identical content as unchanged", () => {
+	// Same episode, id changed between refreshes (migration / URL rotation):
+	// the refresh must NOT bump lastUpdated or re-render.
+	const d = new Date("2026-08-01T00:00:00Z");
+	const existing = [makeEpisode("feed#0", "Ep 1", d)];
+	const fetched = [makeEpisode("feed#guid:g1", "Ep 1", d)];
+	expect(sameRefreshWindow(existing, fetched)).toBe(true);
+});
+
+test("sameRefreshWindow flags a genuinely new episode even when ids drift", () => {
+	const d1 = new Date("2026-08-01T00:00:00Z");
+	const d2 = new Date("2026-08-02T00:00:00Z");
+	const existing = [makeEpisode("feed#0", "Ep 1", d1)];
+	const fetched = [
+		makeEpisode("feed#guid:g2", "Ep 2", d2),
+		makeEpisode("feed#guid:g1", "Ep 1", d1),
+	];
+	expect(sameRefreshWindow(existing, fetched)).toBe(false);
+});
+
 test("mergeEpisodesBounded unions disjoint lists sorted newest-first", () => {
 	const existing = [
 		makeEpisode("old", "Old", new Date("2026-08-01T00:00:00Z")),
@@ -284,13 +345,57 @@ test("date mode boundary: 25 days in, 70 days out", async () => {
 	expect(store.getFeed(id)!.episodes.map((e) => e.title)).toEqual([
 		"In Window",
 	]);
-	// The full cache holds both, but the visible list only shows the in-window
-	// one — fetch-more surfaces the out-of-window one (volatile).
-	expect(store.hasMoreEpisodes(id)).toBe(true);
+	// The 70d episode is ~45 days past the 2-week band beyond the oldest
+	// loaded episode (25d → 39d band): a sparse show must NOT drag it in.
+	expect(store.hasMoreEpisodes(id)).toBe(false);
 	await store.loadMoreEpisodes(id);
 	expect(store.getFeed(id)!.episodes.map((e) => e.title)).toEqual([
 		"In Window",
-		"Out Window",
+	]);
+});
+
+test("date mode: a dormant show (nothing in the window or next band) never fetch-mores", async () => {
+	const store = useFeedStore();
+	const now = Date.now();
+	// Newest episode 100 days old, next 200 days old — both far outside the
+	// 60-day cache window and the 14-day band past its edge.
+	servedEpisodes = [
+		{ title: "Old A", date: new Date(now - 100 * DAY).toISOString() },
+		{ title: "Old B", date: new Date(now - 200 * DAY).toISOString() },
+	];
+	const feedUrl = `http://127.0.0.1:${server!.port}/dormant.xml`;
+	const feed = await store.addFeed(makePodcast(feedUrl), "test-source");
+	expect(feed).not.toBeNull();
+	const id = feed!.id;
+	addedFeedIds.push(id);
+
+	expect(store.getFeed(id)!.episodes.length).toBe(0);
+	expect(store.hasMoreEpisodes(id)).toBe(false);
+	await store.loadMoreEpisodes(id);
+	expect(store.getFeed(id)!.episodes.length).toBe(0);
+});
+
+test("date mode: episodes just outside the window load via the band anchored at the window edge", async () => {
+	const store = useFeedStore();
+	const now = Date.now();
+	// Both episodes are outside the 60-day window (61d / 65d) but inside the
+	// 14-day band past its edge (60d → 74d) — fetch-more reveals them.
+	servedEpisodes = [
+		{ title: "Just Out A", date: new Date(now - 61 * DAY).toISOString() },
+		{ title: "Just Out B", date: new Date(now - 65 * DAY).toISOString() },
+	];
+	const feedUrl = `http://127.0.0.1:${server!.port}/just-out.xml`;
+	const feed = await store.addFeed(makePodcast(feedUrl), "test-source");
+	expect(feed).not.toBeNull();
+	const id = feed!.id;
+	addedFeedIds.push(id);
+
+	expect(store.getFeed(id)!.episodes.length).toBe(0);
+	expect(store.hasMoreEpisodes(id)).toBe(true);
+	await store.loadMoreEpisodes(id);
+	expect(store.getFeed(id)!.episodes.map((e) => e.title)).toEqual([
+		"Just Out A",
+		"Just Out B",
 	]);
 });

@@ -334,6 +439,9 @@ test("date mode: fetch-more steps by a two-week window, not a count", async () =
 test("count mode: only N most-recent episodes are visible, but fetch-more goes beyond", async () => {
 	const store = useFeedStore();
 	const app = useAppStore();
+	// The app store loads persisted prefs asynchronously at import — wait so
+	// the override below isn't clobbered by the load.
+	await app.whenReady();
 	app.updatePreferences({ episodeCacheMode: "count", episodeCacheCount: 25 });

 	const now = Date.now();
@@ -364,3 +472,67 @@ test("count mode: only N most-recent episodes are visible, but fetch-more goes b
 	// Reset to date mode for subsequent tests.
 	app.updatePreferences({ episodeCacheMode: "date" });
 });
+
+test("count mode: Feed list is a GLOBAL top-N that grows N per press, never a far-back dump", async () => {
+	const store = useFeedStore();
+	const app = useAppStore();
+	// Wait out the async pref load (see the single-show count test).
+	await app.whenReady();
+	app.updatePreferences({ episodeCacheMode: "count", episodeCacheCount: 25 });
+
+	const now = Date.now();
+	// Feed A: 200 episodes at 1-day spacing (ages 0–199d). Feed B: 200 at
+	// 1-day spacing shifted 200 days older (ages 200–399d) — every A episode
+	// is newer than every B episode, so the global top-K is deterministic.
+	const serve = (prefix: string, shiftDays: number) =>
+		Array.from({ length: 200 }, (_, i) => ({
+			title: `${prefix} Ep ${200 - i}`,
+			date: new Date(now - (shiftDays + i) * DAY).toISOString(),
+		}));
+	servedEpisodes = serve("A", 0);
+	const aUrl = `http://127.0.0.1:${server!.port}/global-a.xml`;
+	const a = await store.addFeed(makePodcast(aUrl), "test-source");
+	expect(a).not.toBeNull();
+	const aId = a!.id;
+	addedFeedIds.push(aId);
+	servedEpisodes = serve("B", 200);
+	const bUrl = `http://127.0.0.1:${server!.port}/global-b.xml`;
+	const b = await store.addFeed(makePodcast(bUrl), "test-source");
+	expect(b).not.toBeNull();
+	const bId = b!.id;
+	addedFeedIds.push(bId);
+
+	// The Feed page's global list is capped at the configured count (25),
+	// NOT 20 per show (the union would be 40).
+	expect(store.getAllEpisodesChronological().length).toBe(25);
+
+	// Press 1: cap grows to 50 AND every feed's window deepens by 25 — the
+	// list reveals exactly the next 25 most-recent episodes (A's 25 more),
+	// not 25 from every show.
+	await store.loadMoreAllFeeds();
+	expect(store.getAllEpisodesChronological().length).toBe(50);
+	expect(store.getFeed(aId)!.episodes.length).toBe(45);
+	expect(store.getFeed(bId)!.episodes.length).toBe(45);
+	expect(store.hasMoreAcrossAll()).toBe(true);
+
+	// Press 2: cap grows to 75.
+	await store.loadMoreAllFeeds();
+	expect(store.getAllEpisodesChronological().length).toBe(75);
+
+	// Keep pressing until every cache is exhausted. The global cap stays
+	// (never lifts — rendering the full deep union froze the UI), so the
+	// Feed list stays at count×(presses+1) = 25×9 = 225 while the per-show
+	// windows hold everything.
+	let guard = 0;
+	while (store.hasMoreAcrossAll() && guard++ < 30) {
+		await store.loadMoreAllFeeds();
+	}
+	expect(guard).toBeLessThan(30);
+	expect(store.hasMoreAcrossAll()).toBe(false);
+	expect(store.getFeed(aId)!.episodes.length).toBe(200);
+	expect(store.getFeed(bId)!.episodes.length).toBe(200);
+	expect(store.getAllEpisodesChronological().length).toBe(225);
+
+	// Reset to date mode for subsequent tests.
+	app.updatePreferences({ episodeCacheMode: "date" });
+});
--- a/tests/restore-session.test.ts
+++ b/tests/restore-session.test.ts
@@ -31,7 +31,7 @@ process.env.XDG_CONFIG_HOME = CONFIG;
 process.env.XDG_DATA_HOME = DATA;
 process.env.PODTUI_AUDIO_BACKEND = "none";

-// ── Local RSS feed server (episode ids = feedUrl#index) ────────────────────
+// ── Local RSS feed server (episode ids derive from enclosure URLs) ─────────
 let server: ReturnType<typeof Bun.serve> | null = null;
 function feedXml(origin: string): string {
 	const items = ["Episode One", "Episode Two"]