diff --git a/userscript/AGENTS.md b/userscript/AGENTS.md
index 9966c62..98fe033 100644
--- a/userscript/AGENTS.md
+++ b/userscript/AGENTS.md
@@ -70,9 +70,13 @@ Guidance for OpenCode (and Claude Code) working under `userscript/`. See root `A
   Behind a Cloudflare JS challenge no TLS fingerprint
   clears, so the backend polls it through the headless browser.
 - **lightnovelworld.net** (novel script): series `/novel/<slug>/`, chapter
-  `/<slug>-chapter-<n>/` — flat, at the site root. `h1.entry-title` is the clean
-  title on a series page and `<Title> Chapter <n>` on a chapter page. Its series
-  page lists every chapter with an
+  `/<slug>-chapter-<n>/` — flat, at the site root. The chapter path's slug is a
+  Chapter Slug, not an identity: the Series address is read off the page's
+  `a[aria-label='All Chapter']` (fallback: the BreadcrumbList's second crumb),
+  and a Series may publish under several Chapter Slugs. A chapter page with no
+  pointer resolves to `other`, so no Bookmark is offered. `h1.entry-title` is
+  the clean title on a series page and `<Title> Chapter <n>` on a chapter page.
+  Its series page lists every chapter with an
   absolute href, so the backend polls it with the plain TLS client.
 
 ### Second script: `novel-bookmark.user.js`
diff --git a/userscript/novel-bookmark.user.js b/userscript/novel-bookmark.user.js
index cca85f8..07480f5 100644
--- a/userscript/novel-bookmark.user.js
+++ b/userscript/novel-bookmark.user.js
@@ -132,6 +132,23 @@
     },
   };
 
+  // A chapter page's pointer is its own link back to its Series. The href is
+  // page markup, so validate before trusting: the host must be this Site's (a
+  // leading subdomain is allowed, as in `matches`) and the path the
+  // /novel/<slug>/ Series shape. Anything else is not a pointer.
+  function seriesIdFromLnwPointer(href) {
+    if (!href) return null;
+    let u;
+    try {
+      u = new URL(href);
+    } catch (e) {
+      return null;
+    }
+    if (!/(^|\.)lightnovelworld\.net$/.test(u.hostname)) return null;
+    const m = u.pathname.match(/^\/novel\/([^/]+)\/?$/);
+    return m ? m[1] : null;
+  }
+
   const lightnovelworld = {
     site: "lightnovelworld",
     matches: (loc) => /(^|\.)lightnovelworld\.net$/.test(loc.hostname),
@@ -142,16 +159,38 @@
       // words still resolves to the right series.
       let m = path.match(/^\/(.+)-chapter-([0-9]+(?:\.[0-9]+)?)\/?$/);
       if (m) {
+        // The address is not the identity on this Site: the slug in the path
+        // is a Chapter Slug, which can differ from the Series slug and is
+        // never computable from it. The Series address is read from the
+        // page's own pointer — a silent fallback to derivation is the defect
+        // this replaced, not a safety net.
+        const chapterSlug = m[1];
+        const pointer = document.querySelector("a[aria-label='All Chapter']");
+        let seriesId = pointer ? seriesIdFromLnwPointer(pointer.getAttribute("href")) : null;
+        if (!seriesId) {
+          // Fallback: the microdata breadcrumb's second crumb is the Series.
+          // Scoped to the BreadcrumbList because itemprop="item" is not
+          // unique to it (the header nav uses microdata too).
+          const crumb = document.querySelector(
+            '[itemtype="http://schema.org/BreadcrumbList"] a[itemprop="item"][href*="/novel/"]'
+          );
+          seriesId = crumb ? seriesIdFromLnwPointer(crumb.getAttribute("href")) : null;
+        }
+        // Neither pointer present, nor either pointing at a /novel/<slug>/
+        // address on this host: not a page the script understands, so no
+        // Bookmark under an invented identity.
+        if (!seriesId) return { type: "other" };
         const num = parseFloat(m[2]);
         const h1 = document.querySelector("h1.entry-title");
         const heading = h1 ? h1.textContent || "" : "";
         return {
           type: "chapter",
           site: this.site,
-          seriesId: m[1],
+          seriesId: seriesId,
+          chapterSlug: chapterSlug,
           // The heading is "<Series> Chapter <n>"; drop the suffix.
           title: heading.replace(/\s*Chapter\s+[0-9.]+\s*$/i, "").trim(),
-          seriesUrl: "https://lightnovelworld.net/novel/" + m[1] + "/",
+          seriesUrl: "https://lightnovelworld.net/novel/" + seriesId + "/",
           chapterLabel: "Chapter " + m[2],
           chapterNum: isNaN(num) ? null : num,
           chapterUrl: loc.href,
@@ -165,6 +204,7 @@
           type: "series",
           site: this.site,
           seriesId: m[1],
+          chapterSlug: null,
           title: h1 ? (h1.textContent || "").trim() : "",
           seriesUrl: "https://lightnovelworld.net/novel/" + m[1] + "/",
           chapterLabel: null,
diff --git a/userscript/test/novel-logic.test.js b/userscript/test/novel-logic.test.js
index 926e8c7..86d5173 100644
--- a/userscript/test/novel-logic.test.js
+++ b/userscript/test/novel-logic.test.js
@@ -20,8 +20,13 @@ globalThis.location = { href: "about:blank", hostname: "", pathname: "/", origin
 
 let metaTags = {};
 let elements = {};
+// Attribute selectors (the lightnovelworld Series pointer) answer with an
+// element exposing getAttribute, like the meta branch below.
+let attrEls = {};
 globalThis.document = {
   querySelector(sel) {
+    const attr = attrEls[sel];
+    if (attr != null) return attr;
     const m = sel.match(/^meta\[property="([^"]+)"\]$/);
     if (m) {
       const v = metaTags[m[1]];
@@ -52,6 +57,7 @@ function loc(href) {
 function reset() {
   metaTags = {};
   elements = {};
+  attrEls = {};
 }
 
 // ============================================================
@@ -115,11 +121,18 @@ test("lightnovelworld.detect reads a series page", () => {
   assert.equal(p.site, "lightnovelworld");
   assert.equal(p.seriesId, "a-will-eternal");
   assert.equal(p.title, "A Will Eternal");
+  // A series page's address *is* its identity; there is no Chapter Slug.
+  assert.equal(p.chapterSlug, null);
 });
 
 test("lightnovelworld.detect strips the chapter suffix off the heading", () => {
   reset();
   elements = { "h1.entry-title": "A Will Eternal Chapter 1298" };
+  attrEls = {
+    "a[aria-label='All Chapter']": {
+      getAttribute: () => "https://lightnovelworld.net/novel/a-will-eternal/",
+    },
+  };
   const url = "https://lightnovelworld.net/a-will-eternal-chapter-1298/";
   const p = lightnovelworld.detect(loc(url));
   assert.equal(p.type, "chapter");
@@ -130,6 +143,126 @@ test("lightnovelworld.detect strips the chapter suffix off the heading", () => {
   assert.equal(p.seriesUrl, "https://lightnovelworld.net/novel/a-will-eternal/");
 });
 
+test("lightnovelworld.detect reads the Series identity from the page pointer on a chapter page", () => {
+  reset();
+  elements = { "h1.entry-title": "A Will Eternal Chapter 1298" };
+  attrEls = {
+    // Verbatim from the real page (research note §3): the All Chapter anchor
+    // carries the absolute Series address.
+    "a[aria-label='All Chapter']": {
+      getAttribute: () => "https://lightnovelworld.net/novel/a-will-eternal/",
+    },
+  };
+  const url = "https://lightnovelworld.net/a-will-eternal-chapter-1298/";
+  const p = lightnovelworld.detect(loc(url));
+  assert.equal(p.type, "chapter");
+  assert.equal(p.seriesId, "a-will-eternal");
+  assert.equal(p.seriesUrl, "https://lightnovelworld.net/novel/a-will-eternal/");
+  assert.equal(p.chapterSlug, "a-will-eternal");
+  assert.equal(p.chapterNum, 1298);
+});
+
+test("lightnovelworld.detect falls back to the breadcrumb when the pointer is absent", () => {
+  reset();
+  elements = { "h1.entry-title": "My Longevity Simulation Chapter 1" };
+  attrEls = {
+    // Verbatim from the real page (research note §3): position 2 of the
+    // microdata BreadcrumbList is the Series.
+    '[itemtype="http://schema.org/BreadcrumbList"] a[itemprop="item"][href*="/novel/"]': {
+      getAttribute: () => "https://lightnovelworld.net/novel/immortality-simulator/",
+    },
+  };
+  const url = "https://lightnovelworld.net/my-longevity-simulation-chapter-1/";
+  const p = lightnovelworld.detect(loc(url));
+  assert.equal(p.type, "chapter");
+  assert.equal(p.seriesId, "immortality-simulator");
+  assert.equal(p.seriesUrl, "https://lightnovelworld.net/novel/immortality-simulator/");
+  assert.equal(p.chapterSlug, "my-longevity-simulation");
+});
+
+test("lightnovelworld.detect resolves to other when the page carries no pointer", () => {
+  reset();
+  elements = { "h1.entry-title": "My Longevity Simulation Chapter 1" };
+  const p = lightnovelworld.detect(
+    loc("https://lightnovelworld.net/my-longevity-simulation-chapter-1/")
+  );
+  assert.equal(p.type, "other");
+});
+
+test("lightnovelworld pins the divergent novel: the pointer's slug wins over the address's", () => {
+  // Regression pin for the derivation defect (research note §2/§3): the
+  // chapter address is built from "my-longevity-simulation" but the Series
+  // is published as "immortality-simulator". If the adapter ever derives the
+  // identity from the address again, this test goes red.
+  reset();
+  elements = { "h1.entry-title": "My Longevity Simulation Chapter 1" };
+  attrEls = {
+    "a[aria-label='All Chapter']": {
+      getAttribute: () => "https://lightnovelworld.net/novel/immortality-simulator/",
+    },
+  };
+  const url = "https://lightnovelworld.net/my-longevity-simulation-chapter-1/";
+  const p = lightnovelworld.detect(loc(url));
+  assert.equal(p.type, "chapter");
+  assert.equal(p.seriesId, "immortality-simulator");
+  assert.equal(p.seriesUrl, "https://lightnovelworld.net/novel/immortality-simulator/");
+  assert.equal(p.chapterSlug, "my-longevity-simulation");
+  assert.notEqual(p.chapterSlug, p.seriesId);
+});
+
+test("lightnovelworld.detect resolves a novel whose heading ends in a chapter number", () => {
+  // The split novel from research §4.4, chapter 200 (published under the
+  // current slug). Its heading ends "…Not Them All Chapter 200", which would
+  // false-match a selector that looks for the text "All Chapter".
+  reset();
+  elements = {
+    "h1.entry-title": "All Jobs and Classes I Just Wanted One Skill Not Them All Chapter 200",
+  };
+  attrEls = {
+    "a[aria-label='All Chapter']": {
+      getAttribute: () =>
+        "https://lightnovelworld.net/novel/all-jobs-and-classes-i-just-wanted-one-skill-not-them-all/",
+    },
+  };
+  const url =
+    "https://lightnovelworld.net/all-jobs-and-classes-i-just-wanted-one-skill-not-them-all-chapter-200/";
+  const p = lightnovelworld.detect(loc(url));
+  assert.equal(p.type, "chapter");
+  assert.equal(p.seriesId, "all-jobs-and-classes-i-just-wanted-one-skill-not-them-all");
+  assert.equal(p.title, "All Jobs and Classes I Just Wanted One Skill Not Them All");
+  assert.equal(p.chapterNum, 200);
+  assert.equal(p.chapterSlug, "all-jobs-and-classes-i-just-wanted-one-skill-not-them-all");
+});
+
+test("lightnovelworld.detect resolves both Chapter Slugs of the split novel to one Series", () => {
+  // Research note §4.4: this Series serves chapters 1-99 under one Chapter
+  // Slug and 100-423 under another; both chapter addresses are live and both
+  // point back at the same Series. An old deep link must not get a different
+  // identity than a current one.
+  reset();
+  elements = { "h1.entry-title": "All Jobs and Classes I Just Wanted One Skill Not Chapter 1" };
+  attrEls = {
+    "a[aria-label='All Chapter']": {
+      getAttribute: () =>
+        "https://lightnovelworld.net/novel/all-jobs-and-classes-i-just-wanted-one-skill-not-them-all/",
+    },
+  };
+  const oldSlug = lightnovelworld.detect(
+    loc("https://lightnovelworld.net/all-jobs-and-classes-i-just-wanted-one-skill-not-chapter-1/")
+  );
+  const currentSlug = lightnovelworld.detect(
+    loc(
+      "https://lightnovelworld.net/all-jobs-and-classes-i-just-wanted-one-skill-not-them-all-chapter-404/"
+    )
+  );
+  assert.equal(oldSlug.type, "chapter");
+  assert.equal(oldSlug.seriesId, "all-jobs-and-classes-i-just-wanted-one-skill-not-them-all");
+  assert.equal(oldSlug.chapterSlug, "all-jobs-and-classes-i-just-wanted-one-skill-not");
+  assert.equal(currentSlug.type, "chapter");
+  assert.equal(currentSlug.seriesId, "all-jobs-and-classes-i-just-wanted-one-skill-not-them-all");
+  assert.equal(currentSlug.chapterSlug, "all-jobs-and-classes-i-just-wanted-one-skill-not-them-all");
+});
+
 test("lightnovelworld.detect returns other for non-series paths", () => {
   reset();
   assert.equal(lightnovelworld.detect(loc("https://lightnovelworld.net/")).type, "other");