diff --git a/userscript/novel-bookmark.user.js b/userscript/novel-bookmark.user.js
index 3d4884d..0241f11 100644
--- a/userscript/novel-bookmark.user.js
+++ b/userscript/novel-bookmark.user.js
@@ -244,6 +244,102 @@
     return ADAPTERS.find((a) => a.site === site) || null;
   }
 
+  // A stale lightnovelworld row is one keyed under the Chapter Slug its
+  // address was built from, while the page's pointer names a different
+  // Series. All three storage sites must move together: the cache row alone
+  // leaves a queued write replaying under a key whose row no longer exists
+  // (that write is silently lost), and a last-checked timestamp left behind
+  // re-fetches the repaired row on the next visit. A repair must never cost a
+  // Reader the chapter they were tracking, so when a row already holds the
+  // repaired key the two rows merge and the farther-ahead progress wins.
+  // Pure: no storage access, no module state, no clock.
+  function repairLnwStaleRow(list, queue, lastChecked, page) {
+    if (
+      !page ||
+      page.site !== "lightnovelworld" ||
+      !page.chapterSlug ||
+      !page.seriesId ||
+      page.chapterSlug === page.seriesId
+    ) {
+      return { list, queue, lastChecked };
+    }
+    const oldKey = "lightnovelworld:" + page.chapterSlug;
+    const newKey = "lightnovelworld:" + page.seriesId;
+    const stale = list.find((b) => b.key === oldKey);
+    if (!stale) return { list, queue, lastChecked };
+
+    let listOut;
+    const existing = list.find((b) => b.key === newKey);
+    if (existing) {
+      // Duplicate case (spec user story 2): one row must survive, and it is
+      // the one already under the repaired key — with the stale row's
+      // progress carried across when it is ahead, favourite OR'd, and the
+      // stronger lifecycle bucket kept (finished > archived > reading, so a
+      // merge can never silently un-archive or un-finish a row).
+      const merged = Object.assign({}, existing);
+      if (
+        existing.last_chapter_num == null ||
+        (stale.last_chapter_num != null && stale.last_chapter_num > existing.last_chapter_num)
+      ) {
+        merged.last_chapter = stale.last_chapter;
+        merged.last_chapter_num = stale.last_chapter_num;
+        merged.last_chapter_url = stale.last_chapter_url;
+      }
+      merged.favorite = !!(existing.favorite || stale.favorite);
+      const rank = (s) => ({ finished: 2, archived: 1, reading: 0 }[s || "reading"] || 0);
+      merged.status = rank(stale.status) > rank(existing.status) ? stale.status : existing.status;
+      merged.updated_at = Math.max(existing.updated_at || 0, stale.updated_at || 0);
+      listOut = list.filter((b) => b.key !== oldKey).map((b) => (b.key === newKey ? merged : b));
+    } else {
+      listOut = list.map((b) =>
+        b.key === oldKey
+          ? Object.assign({}, b, {
+              key: newKey,
+              series_id: page.seriesId,
+              series_url: page.seriesUrl,
+            })
+          : b
+      );
+    }
+
+    let queueOut = queue;
+    const oldEntry = queue.find((e) => e.key === oldKey);
+    if (oldEntry) {
+      const survivor = queue.find((x) => x.key === newKey);
+      if (!survivor) {
+        queueOut = queue.map((e) => (e.key === oldKey ? Object.assign({}, e, { key: newKey }) : e));
+      } else {
+        // Both keys hold a marker and one row survives, so the two collapse
+        // into one entry under the repaired key (the queue's one-entry-per-key
+        // invariant). sendStatus is sticky — an archive intent from either
+        // marker survives, the queue's own rule — and the worse attempts
+        // count wins. The stale-key marker's op is dropped: the row it
+        // described is retired by the merge itself.
+        queueOut = queue
+          .filter((e) => e.key !== oldKey && e.key !== newKey)
+          .concat([
+            {
+              key: newKey,
+              op: survivor.op,
+              sendStatus: survivor.sendStatus || oldEntry.sendStatus,
+              attempts: Math.max(survivor.attempts || 0, oldEntry.attempts || 0),
+            },
+          ]);
+      }
+    }
+
+    let lastCheckedOut = lastChecked;
+    if (oldKey in lastChecked) {
+      lastCheckedOut = Object.assign({}, lastChecked);
+      // Max, not overwrite: a timestamp already under the repaired key must
+      // not be rolled back to an older one.
+      lastCheckedOut[newKey] = Math.max(lastCheckedOut[newKey] || 0, lastCheckedOut[oldKey]);
+      delete lastCheckedOut[oldKey];
+    }
+
+    return { list: listOut, queue: queueOut, lastChecked: lastCheckedOut };
+  }
+
   // Highest chapter the site lists, or null when the markup yields nothing.
   // seriesId is only consulted by adapters whose pages carry other series'
   // chapter links; the rest ignore it.
@@ -1243,7 +1339,8 @@
   // Refresh + navigation
   // ============================================================
 
-  async function refresh() {
+  async function refresh(awaitFirst) {
+    if (awaitFirst) await awaitFirst; // repair sync lands before we adopt the server's view of it
     await drain(); // push what we owe before adopting the server's view of it
     loading = true;
     render();
@@ -1258,9 +1355,41 @@
     }
   }
 
+  // Runs the repair on every navigation, silently: rewrites a stale
+  // lightnovelworld row to the page's discovered identity, persists all three
+  // sites, and syncs through the queue-backed path so an offline repair parks
+  // and replays later. No toast — the Reader never asked for this. Returns
+  // the sync promise (or null when nothing changed) so init can hold the
+  // server view until the repair has landed. When the transform returns its
+  // inputs unchanged there is nothing to do.
+  function applyLnwStaleRowRepair() {
+    const lastChecked = loadLastChecked();
+    const out = repairLnwStaleRow(state.list, queue, lastChecked, state.page);
+    if (out.list === state.list && out.queue === queue && out.lastChecked === lastChecked) {
+      return null;
+    }
+    state.list = out.list;
+    reindex(); // byKey answers under the old key until rebuilt
+    saveCache(state.list);
+    queue.splice(0, queue.length, ...out.queue); // closures hold this array instance
+    saveQueue(queue);
+    saveLastChecked(out.lastChecked);
+    // Queue-backed sync, outcome swallowed: the repaired row is PUT (with its
+    // bucket when archived — the only status a userscript write may send) and
+    // the old server bookmark is deleted so no duplicate survives on the
+    // wire. The delete parks under the retired key while offline — the
+    // teardown of the old identity, not a new record of the Chapter Slug.
+    const key = keyOf(state.page);
+    return Promise.all([
+      pushBookmark(key, statusOf(state.byKey[key]) === "archived"),
+      pushDelete("lightnovelworld:" + state.page.chapterSlug),
+    ]).catch(() => {});
+  }
+
   let lastUrl = location.href;
   function onNavigate() {
     state.page = detect();
+    applyLnwStaleRowRepair();
     render();
     maybeAutoUpdate();
     maybeCaptureLatestOnSeriesPage();
@@ -1373,13 +1502,14 @@
   function init() {
     buildUI();
     state.page = detect();
+    const repair = applyLnwStaleRowRepair();
     render();
     installNavWatcher();
     installLongPress();
     window.addEventListener("online", drain); // signal returned while the page stayed open
     // Sync first: both auto-record and the latest-chapter checks below need to
     // know which series are bookmarked and how fresh they are.
-    refresh().then(() => {
+    refresh(repair).then(() => {
       maybeAutoUpdate();
       maybeCaptureLatestOnSeriesPage();
       backgroundRefreshLatest();
@@ -1620,7 +1750,7 @@
   // Exposes pure logic only — see userscript/test/novel-logic.test.js.
   // ============================================================
   if (typeof window === "undefined" && typeof module === "object" && module.exports) {
-    module.exports = { novelfull, lightnovelworld, anchorsFromHTML, statusOf, kindOf, maxChapter, escapeRe };
+    module.exports = { novelfull, lightnovelworld, anchorsFromHTML, statusOf, kindOf, maxChapter, escapeRe, repairLnwStaleRow };
   }
 
   // ============================================================
diff --git a/userscript/test/novel-logic.test.js b/userscript/test/novel-logic.test.js
index 9b8ef5b..61380b1 100644
--- a/userscript/test/novel-logic.test.js
+++ b/userscript/test/novel-logic.test.js
@@ -47,6 +47,7 @@ const {
   lightnovelworld,
   kindOf,
   maxChapter,
+  repairLnwStaleRow,
 } = require("../novel-bookmark.user.js");
 
 function loc(href) {
@@ -331,6 +332,213 @@ test("latestChapterFromAnchors returns null when nothing matches", () => {
   assert.equal(maxChapter([], /chapter-([0-9.]+)/), null);
 });
 
+// ============================================================
+// repairLnwStaleRow — the row migration (spec seam 3)
+// ============================================================
+
+// A row as bookmarkCurrent builds it, keyed under the invented Chapter Slug
+// identity the old adapter derived from the chapter address.
+function staleRow(over) {
+  return Object.assign(
+    {
+      key: "lightnovelworld:my-longevity-simulation",
+      site: "lightnovelworld",
+      kind: "novel",
+      series_id: "my-longevity-simulation",
+      title: "My Longevity Simulation",
+      series_url: "https://lightnovelworld.net/novel/my-longevity-simulation/",
+      last_chapter: "Chapter 7",
+      last_chapter_num: 7,
+      last_chapter_url: "https://lightnovelworld.net/my-longevity-simulation-chapter-7/",
+      updated_at: 1000,
+    },
+    over
+  );
+}
+
+// The divergent novel from research §3: the address's slug is a Chapter Slug,
+// the page pointer names the real Series.
+function lnwPage(over) {
+  return Object.assign(
+    {
+      type: "chapter",
+      site: "lightnovelworld",
+      seriesId: "immortality-simulator",
+      chapterSlug: "my-longevity-simulation",
+      seriesUrl: "https://lightnovelworld.net/novel/immortality-simulator/",
+    },
+    over
+  );
+}
+
+test("repairLnwStaleRow rewrites the row, the queue entry and the last-checked map together", () => {
+  const list = [staleRow()];
+  const queue = [
+    { key: "lightnovelworld:my-longevity-simulation", op: "put", sendStatus: false, attempts: 2 },
+  ];
+  const lastChecked = { "lightnovelworld:my-longevity-simulation": 12345 };
+  const out = repairLnwStaleRow(list, queue, lastChecked, lnwPage());
+  assert.equal(out.list.length, 1);
+  assert.equal(out.list[0].key, "lightnovelworld:immortality-simulator");
+  assert.equal(out.list[0].series_id, "immortality-simulator");
+  assert.equal(out.list[0].series_url, "https://lightnovelworld.net/novel/immortality-simulator/");
+  assert.deepEqual(out.queue, [
+    { key: "lightnovelworld:immortality-simulator", op: "put", sendStatus: false, attempts: 2 },
+  ]);
+  assert.deepEqual(out.lastChecked, { "lightnovelworld:immortality-simulator": 12345 });
+});
+
+test("repairLnwStaleRow keeps Progress, Favourite and Lifecycle bucket on the rewritten row", () => {
+  const stale = staleRow({
+    last_chapter: "Chapter 42",
+    last_chapter_num: 42,
+    last_chapter_url: "https://lightnovelworld.net/my-longevity-simulation-chapter-42/",
+    favorite: true,
+    status: "archived",
+    updated_at: 777,
+  });
+  const out = repairLnwStaleRow([stale], [], {}, lnwPage());
+  const b = out.list[0];
+  assert.equal(b.last_chapter, "Chapter 42");
+  assert.equal(b.last_chapter_num, 42);
+  assert.equal(
+    b.last_chapter_url,
+    "https://lightnovelworld.net/my-longevity-simulation-chapter-42/"
+  );
+  assert.equal(b.favorite, true);
+  assert.equal(b.status, "archived");
+  assert.equal(b.updated_at, 777);
+  assert.equal(b.title, "My Longevity Simulation");
+});
+
+test("repairLnwStaleRow changes nothing when the Chapter Slug and Series slug agree", () => {
+  const list = [
+    staleRow({ key: "lightnovelworld:a-will-eternal", series_id: "a-will-eternal" }),
+  ];
+  const queue = [{ key: "lightnovelworld:a-will-eternal", op: "put", sendStatus: true, attempts: 1 }];
+  const lastChecked = { "lightnovelworld:a-will-eternal": 99 };
+  const out = repairLnwStaleRow(
+    list,
+    queue,
+    lastChecked,
+    lnwPage({
+      chapterSlug: "a-will-eternal",
+      seriesId: "a-will-eternal",
+      seriesUrl: "https://lightnovelworld.net/novel/a-will-eternal/",
+    })
+  );
+  assert.equal(out.list, list); // same references, nothing rewritten
+  assert.equal(out.queue, queue);
+  assert.equal(out.lastChecked, lastChecked);
+});
+
+test("repairLnwStaleRow changes nothing when no row sits under the old key", () => {
+  const list = [
+    staleRow({
+      key: "lightnovelworld:immortality-simulator",
+      series_id: "immortality-simulator",
+      series_url: "https://lightnovelworld.net/novel/immortality-simulator/",
+    }),
+  ];
+  const lastChecked = { "lightnovelworld:immortality-simulator": 99 };
+  const out = repairLnwStaleRow(list, [], lastChecked, lnwPage());
+  assert.equal(out.list, list);
+  assert.equal(out.queue.length, 0);
+  assert.equal(out.lastChecked, lastChecked);
+});
+
+test("repairLnwStaleRow ignores a page that carries no Chapter Slug", () => {
+  const list = [
+    staleRow({
+      key: "lightnovelworld:immortality-simulator",
+      series_id: "immortality-simulator",
+    }),
+  ];
+  const lastChecked = { "lightnovelworld:immortality-simulator": 99 };
+  // A series page (chapterSlug null) and another site both stay untouched.
+  const series = repairLnwStaleRow(list, [], lastChecked, lnwPage({ chapterSlug: null }));
+  const other = repairLnwStaleRow(list, [], lastChecked, {
+    type: "chapter",
+    site: "novelfull",
+    seriesId: "x",
+  });
+  assert.equal(series.list, list);
+  assert.equal(other.list, list);
+});
+
+test("repairLnwStaleRow still moves the row and the last-checked map when the queue has no entry", () => {
+  const out = repairLnwStaleRow(
+    [staleRow()],
+    [],
+    { "lightnovelworld:my-longevity-simulation": 5 },
+    lnwPage()
+  );
+  assert.equal(out.list[0].key, "lightnovelworld:immortality-simulator");
+  assert.deepEqual(out.queue, []);
+  assert.deepEqual(out.lastChecked, { "lightnovelworld:immortality-simulator": 5 });
+});
+
+test("repairLnwStaleRow carries a queued change to the repaired identity with its marker intact", () => {
+  const queue = [
+    { key: "lightnovelworld:my-longevity-simulation", op: "put", sendStatus: true, attempts: 3 },
+  ];
+  const out = repairLnwStaleRow([staleRow()], queue, {}, lnwPage());
+  assert.deepEqual(out.queue, [
+    { key: "lightnovelworld:immortality-simulator", op: "put", sendStatus: true, attempts: 3 },
+  ]);
+});
+
+test("repairLnwStaleRow merges a duplicate under the repaired key, keeping the farther-ahead progress", () => {
+  const canonical = staleRow({
+    key: "lightnovelworld:immortality-simulator",
+    series_id: "immortality-simulator",
+    series_url: "https://lightnovelworld.net/novel/immortality-simulator/",
+    last_chapter: "Chapter 5",
+    last_chapter_num: 5,
+    last_chapter_url: "https://lightnovelworld.net/immortality-simulator-chapter-5/",
+    favorite: false,
+  });
+  const stale = staleRow({
+    last_chapter: "Chapter 42",
+    last_chapter_num: 42,
+    last_chapter_url: "https://lightnovelworld.net/my-longevity-simulation-chapter-42/",
+    favorite: true,
+    status: "archived",
+  });
+  const queue = [
+    { key: "lightnovelworld:my-longevity-simulation", op: "put", sendStatus: true, attempts: 3 },
+    { key: "lightnovelworld:immortality-simulator", op: "put", sendStatus: false, attempts: 0 },
+  ];
+  const out = repairLnwStaleRow([canonical, stale], queue, {}, lnwPage());
+  assert.equal(out.list.length, 1);
+  const merged = out.list[0];
+  assert.equal(merged.key, "lightnovelworld:immortality-simulator");
+  assert.equal(merged.last_chapter_num, 42); // the stale row is ahead — progress must not be lost
+  assert.equal(merged.favorite, true); // favourite survives from either row
+  assert.equal(merged.status, "archived"); // the stronger bucket survives
+  // One marker under the repaired key: sendStatus is sticky (the archive
+  // intent from the stale-key marker survives) and the worse attempts count
+  // wins — the queue's own coalescing rules.
+  assert.deepEqual(out.queue, [
+    { key: "lightnovelworld:immortality-simulator", op: "put", sendStatus: true, attempts: 3 },
+  ]);
+});
+
+test("repairLnwStaleRow does not regress progress when the repaired-key row is ahead", () => {
+  const canonical = staleRow({
+    key: "lightnovelworld:immortality-simulator",
+    series_id: "immortality-simulator",
+    series_url: "https://lightnovelworld.net/novel/immortality-simulator/",
+    last_chapter: "Chapter 100",
+    last_chapter_num: 100,
+    last_chapter_url: "https://lightnovelworld.net/immortality-simulator-chapter-100/",
+  });
+  const stale = staleRow({ last_chapter: "Chapter 42", last_chapter_num: 42 });
+  const out = repairLnwStaleRow([canonical, stale], [], {}, lnwPage());
+  assert.equal(out.list.length, 1);
+  assert.equal(out.list[0].last_chapter_num, 100);
+});
+
 // ============================================================
 // kindOf
 // ============================================================