diff --git a/src/main/native-doc.ts b/src/main/native-doc.ts
index 5708ca3..f841655 100644
--- a/src/main/native-doc.ts
+++ b/src/main/native-doc.ts
@@ -56,6 +56,42 @@ export const CALLOUT_TITLE_CLASS = "callout-title";
 // into [[wikilinks]]; the wikilink plugin turns [[text]] into it on parse.
 export const CHAPTER_LINK_PREFIX = "folio:chapter/";
 
+// ---- Chapter presentation helpers ----------------------------------------
+// Shared by every assembled/exported rendering of a chapter (Full Book view,
+// PDF print, DOCX/ODT) so "does this chapter already carry its own title?"
+// has exactly one answer everywhere. Before this lived in two files with
+// different rules, DOCX and PDF could disagree about injecting the title.
+
+/** Concatenated plain text of a node subtree (atom leaves contribute nothing). */
+export function nativeNodeText(node: FolioNode): string {
+  if (node.text) return node.text;
+  let t = "";
+  for (const c of node.content ?? []) t += nativeNodeText(c);
+  return t;
+}
+
+/** Whether any top-level heading in the content already matches the title
+ *  (case/space-insensitive). If true, renderers must not inject a duplicate
+ *  title heading ahead of the content. */
+export function nativeHasTitleHeading(content: FolioNode[], title: string): boolean {
+  const t = title.trim().toLowerCase();
+  if (!t) return false;
+  for (const n of content) {
+    if (n.type === "heading" && nativeNodeText(n).trim().toLowerCase() === t) return true;
+  }
+  return false;
+}
+
+/** Top-level nodes for one chapter, injecting a title heading when the
+ *  content does not already provide one. */
+export function buildChapterNativeContent(content: FolioNode[], title: string): FolioNode[] {
+  if (nativeHasTitleHeading(content, title)) return content.slice();
+  return [
+    { type: "heading", attrs: { level: 1 }, content: [{ type: "text", text: title }] },
+    ...content,
+  ];
+}
+
 // Each entry migrates the document FROM its key version TO key+1.
 // Entries are additive and must be non-destructive.
 const MIGRATIONS: Record<number, (doc: FolioChapterDoc) => FolioChapterDoc> = {};
diff --git a/src/main/office-export.ts b/src/main/office-export.ts
index f12d6c3..f6fc2fe 100644
--- a/src/main/office-export.ts
+++ b/src/main/office-export.ts
@@ -35,6 +35,7 @@ import {
   CALLOUT_TITLE_CLASS,
   CHAPTER_LINK_PREFIX,
 } from "./native-doc.js";
+import { nativeHasTitleHeading } from "./native-doc.js";
 import type { FolioMark, FolioNode } from "./native-doc.js";
 
 const MONO_FONT = "Consolas";
@@ -192,14 +193,13 @@ function nodeText(node: FolioNode): string {
   return t;
 }
 
-// Whether the chapter's native content already opens with a heading matching
-// its title, in which case we must not inject a duplicate title heading.
+// Whether to prepend a title heading. Delegates to the shared predicate so
+// DOCX/ODT answer identically to the Full Book view and PDF print (the old
+// local copy only inspected the FIRST node, so a chapter whose self-title
+// heading sat deeper in the document got a duplicate injected here while the
+// other paths correctly skipped it).
 function needsTitleInjection(content: FolioNode[], title: string): boolean {
-  const t = title.trim().toLowerCase();
-  if (!t) return false;
-  const first = content[0];
-  if (first && first.type === "heading" && nodeText(first).trim().toLowerCase() === t) return false;
-  return true;
+  return !nativeHasTitleHeading(content, title);
 }
 
 function headingLevel(level: number) {
diff --git a/src/renderer/native-assembly.ts b/src/renderer/native-assembly.ts
index 8315fb2..324144e 100644
--- a/src/renderer/native-assembly.ts
+++ b/src/renderer/native-assembly.ts
@@ -5,8 +5,18 @@
 // These helpers are kept free of DOM/IPC so they can be unit-tested directly
 // and reused by the renderer (book.ts).
 import type { FolioNode } from "../main/native-doc.js";
+import {
+  nativeNodeText,
+  nativeHasTitleHeading,
+  buildChapterNativeContent,
+} from "../main/native-doc.js";
 import type { WikilinkTarget } from "./wikilinks.js";
 
+// The title-heading helpers are shared with the DOCX/ODT exporter and live
+// next to the schema in native-doc.ts. Re-exported so existing consumers
+// (and the fullbook test entry) keep their import paths.
+export { nativeNodeText, nativeHasTitleHeading, buildChapterNativeContent };
+
 export interface FullBookChapterInput {
   id: string;
   title: string;
@@ -22,33 +32,15 @@ export interface FullBookAssembly {
 
 // Concatenate the plain text of a native node tree (used for word/char counts).
 // Atom leaf nodes (chapterBreak, image, horizontal rule, …) carry no text.
-export function nativeNodeText(node: FolioNode): string {
-  if (node.text) return node.text;
-  let t = "";
-  for (const c of node.content ?? []) t += nativeNodeText(c);
-  return t;
-}
+// (Implementation lives in native-doc.ts; re-exported above.)
 
 // Whether the native content already opens with a heading matching its title,
 // in which case we must not inject a duplicate title heading.
-export function nativeHasTitleHeading(content: FolioNode[], title: string): boolean {
-  const t = title.trim().toLowerCase();
-  if (!t) return false;
-  for (const n of content) {
-    if (n.type === "heading" && nativeNodeText(n).trim().toLowerCase() === t) return true;
-  }
-  return false;
-}
+// (Implementation lives in native-doc.ts; re-exported above.)
 
-// Build the top-level nodes for one chapter in the Full Book, injecting a title
+// Top-level nodes for one chapter in the Full Book, injecting a title
 // heading when the content does not already provide one.
-export function buildChapterNativeContent(content: FolioNode[], title: string): FolioNode[] {
-  if (nativeHasTitleHeading(content, title)) return content.slice();
-  return [
-    { type: "heading", attrs: { level: 1 }, content: [{ type: "text", text: title }] },
-    ...content,
-  ];
-}
+// (Implementation lives in native-doc.ts; re-exported above.)
 
 // A ChapterBreak anchor marking where a chapter begins in the assembled view.
 export function chapterBreakNode(id: string, title: string, first: boolean): FolioNode {