diff --git a/lib/export/narration.ts b/lib/export/narration.ts
new file mode 100644
index 0000000000..fd4306aa3b
--- /dev/null
+++ b/lib/export/narration.ts
@@ -0,0 +1,64 @@
+/**
+ * Shared narration walk for the export family.
+ *
+ * The script (.md/.docx) exporter and the PPTX speaker-notes exporter each
+ * used to hand-roll "iterate `scene.actions`, keep `type === 'speech'`,
+ * join the text" — two copies of the same domain traversal that could drift on
+ * what counts as narration (issue #1142). Both now delegate here.
+ *
+ * The two callers genuinely differ in two knobs, both preserved explicitly:
+ *
+ * - `keepWhitespaceOnly` — the script exporter drops whitespace-only speech
+ *   (no empty paragraphs in the document); the PPTX exporter historically kept
+ *   it. Defaults to `true` so the PPTX path is unchanged.
+ * - `trim` — the script exporter trims each kept part before joining; the PPTX
+ *   exporter does not. Defaults to `false` so the PPTX path is unchanged.
+ *
+ * Defaults therefore reproduce the PPTX behaviour, and the script exporter opts
+ * into its stricter behaviour at its call site.
+ *
+ * Unlike the script exporter's previous inline walk, a `speech` action with a
+ * missing `text` field is tolerated instead of throwing (the old code called
+ * `.trim()` on `undefined`). Well-typed scenes are unaffected.
+ */
+export interface SpeechTextOptions {
+  /** Keep speech actions whose `text` is empty or whitespace-only. */
+  readonly keepWhitespaceOnly?: boolean;
+  /** Trim each kept speech text before joining. */
+  readonly trim?: boolean;
+}
+
+/** Minimal structural shape of a speech action for the walk. */
+interface SpeechLike {
+  readonly type: string;
+  readonly text?: string;
+}
+
+/** Minimal structural shape of a scene for the walk. */
+interface SceneLike {
+  readonly actions?: readonly SpeechLike[] | undefined;
+}
+
+/**
+ * Concatenate a scene's speech text in playback order, one part per speech
+ * action, joined with `\n`.
+ *
+ * Single source of truth for "what counts as narration" — see #1142.
+ */
+export function collectSpeechText(
+  scene: SceneLike | null | undefined,
+  options: SpeechTextOptions = {},
+): string {
+  const { keepWhitespaceOnly = true, trim = false } = options;
+  const actions = scene?.actions;
+  if (!actions || actions.length === 0) return '';
+
+  const parts: string[] = [];
+  for (const action of actions) {
+    if (action.type !== 'speech') continue;
+    const text = action.text ?? '';
+    if (!keepWhitespaceOnly && !text.trim()) continue;
+    parts.push(trim ? text.trim() : text);
+  }
+  return parts.join('\n');
+}
diff --git a/lib/export/use-export-pptx.ts b/lib/export/use-export-pptx.ts
index 96f0e48cc0..b2120f92f9 100644
--- a/lib/export/use-export-pptx.ts
+++ b/lib/export/use-export-pptx.ts
@@ -19,13 +19,13 @@ import {
   type PPTElementLink,
 } from '@openmaic/dsl';
 import type { Scene, SlideContent } from '@/lib/types/stage';
-import type { SpeechAction } from '@/lib/types/action';
 import { getElementRange, getLineElementPath, getTableSubThemeColor } from '@/lib/utils/element';
 import { type AST, toAST } from '@/lib/export/html-parser';
 import { type SvgPoints, toPoints, getSvgPathRange } from '@/lib/export/svg-path-parser';
 import { svg2Base64 } from '@/lib/export/svg2base64';
 import { latexToOmml } from '@/lib/export/latex-to-omml';
 import { createLogger } from '@/lib/logger';
+import { collectSpeechText } from './narration';
 import { inlineHtmlAssets, createAssetFetcher } from './inline-assets';
 import type { FetchAsset } from './inline-assets';
 import { createProxiedFetch } from './proxied-fetch';
@@ -370,16 +370,14 @@ function isSVGImage(url: string) {
  * Extract speaker notes text from a scene's actions.
  * Concatenates speech text and action labels into plain text.
  */
+/**
+ * Speaker notes for one slide: the scene's speech text in action order.
+ * Delegates to the shared narration walk in `./narration` (#1142) with its
+ * historical options — whitespace-only speech is kept and parts are not
+ * trimmed, matching the pre-refactor notes output.
+ */
 function buildSpeakerNotes(scene: Scene): string {
-  if (!scene.actions || scene.actions.length === 0) return '';
-
-  const parts: string[] = [];
-  for (const action of scene.actions) {
-    if (action.type === 'speech') {
-      parts.push((action as SpeechAction).text);
-    }
-  }
-  return parts.join('\n');
+  return collectSpeechText(scene);
 }
 
 async function blobToDataUrl(blob: Blob): Promise<string> {
diff --git a/lib/export/use-export-script.ts b/lib/export/use-export-script.ts
index beb1af719e..6c53e02344 100644
--- a/lib/export/use-export-script.ts
+++ b/lib/export/use-export-script.ts
@@ -18,6 +18,7 @@ import { useStageStore } from '@/lib/store';
 import { useMediaGenerationStore } from '@/lib/store/media-generation';
 import { useI18n } from '@/lib/hooks/use-i18n';
 import { createLogger } from '@/lib/logger';
+import { collectSpeechText } from './narration';
 import type { Scene } from '@/lib/types/stage';
 
 const log = createLogger('ExportScript');
@@ -64,6 +65,11 @@ export function isScriptExportReady(
  * Collect each scene's narration: concatenate its `SpeechAction.text` values in
  * action order. Scenes with no speech text are omitted entirely. `slideFallback`
  * supplies the locale-appropriate label for scenes with an empty title.
+ *
+ * The speech walk itself lives in `./narration` so this exporter and the PPTX
+ * speaker-notes exporter can't drift on what counts as narration (#1142).
+ * Whitespace-only speech is dropped and kept text is trimmed — see the
+ * `keepWhitespaceOnly` / `trim` options there.
  */
 export function collectSceneScripts(
   scenes: Scene[],
@@ -71,13 +77,7 @@ export function collectSceneScripts(
 ): SceneScript[] {
   const scripts: SceneScript[] = [];
   for (const scene of scenes) {
-    const parts: string[] = [];
-    for (const action of scene.actions ?? []) {
-      if (action.type === 'speech' && action.text.trim()) {
-        parts.push(action.text.trim());
-      }
-    }
-    const text = parts.join('\n');
+    const text = collectSpeechText(scene, { keepWhitespaceOnly: false, trim: true });
     if (!text) continue;
     scripts.push({
       sceneId: scene.id,
diff --git a/tests/export/narration.test.ts b/tests/export/narration.test.ts
new file mode 100644
index 0000000000..a3c1a1686f
--- /dev/null
+++ b/tests/export/narration.test.ts
@@ -0,0 +1,99 @@
+import { describe, it, expect } from 'vitest';
+import { collectSpeechText } from '@/lib/export/narration';
+import type { Scene } from '@/lib/types/stage';
+import type { SpeechAction } from '@/lib/types/action';
+
+function speechAction(id: string, text: string): SpeechAction {
+  return { id, type: 'speech', text };
+}
+
+function scene(overrides: Partial<Scene> = {}): Scene {
+  return {
+    id: 's1',
+    stageId: 'stg1',
+    title: 'Scene One',
+    order: 1,
+    type: 'slide',
+    content: {
+      type: 'slide',
+      canvas: { width: 960, height: 540, elements: [] },
+      animations: [],
+    },
+    actions: [],
+    ...overrides,
+  } as unknown as Scene;
+}
+
+describe('collectSpeechText', () => {
+  it('returns an empty string for a scene with no actions', () => {
+    expect(collectSpeechText(scene({ actions: [] }))).toBe('');
+  });
+
+  it('returns an empty string for a scene with undefined actions', () => {
+    expect(collectSpeechText(scene({ actions: undefined }))).toBe('');
+  });
+
+  it('tolerates a missing scene', () => {
+    expect(collectSpeechText(null)).toBe('');
+    expect(collectSpeechText(undefined)).toBe('');
+  });
+
+  it('collects only speech text, in action order', () => {
+    const s = scene({
+      actions: [
+        speechAction('a1', 'First.'),
+        { id: 'a2', type: 'spotlight', elementId: 'e1' },
+        speechAction('a3', 'Second.'),
+        { id: 'a4', type: 'wb_draw_text', content: 'board', x: 0, y: 0 },
+      ],
+    });
+    expect(collectSpeechText(s)).toBe('First.\nSecond.');
+  });
+
+  it('keeps whitespace-only speech by default (PPTX behaviour)', () => {
+    const s = scene({ actions: [speechAction('a1', '   ')] });
+    expect(collectSpeechText(s)).toBe('   ');
+  });
+
+  it('drops whitespace-only speech with keepWhitespaceOnly: false (script behaviour)', () => {
+    const s = scene({ actions: [speechAction('a1', '   '), speechAction('a2', 'Kept')] });
+    expect(collectSpeechText(s, { keepWhitespaceOnly: false })).toBe('Kept');
+  });
+
+  it('drops empty-string speech with keepWhitespaceOnly: false', () => {
+    const s = scene({ actions: [speechAction('a1', ''), speechAction('a2', 'Kept')] });
+    expect(collectSpeechText(s, { keepWhitespaceOnly: false })).toBe('Kept');
+  });
+
+  it('does not trim parts by default (PPTX behaviour)', () => {
+    const s = scene({ actions: [speechAction('a1', '  Hello  ')] });
+    expect(collectSpeechText(s)).toBe('  Hello  ');
+  });
+
+  it('trims each part with trim: true (script behaviour)', () => {
+    const s = scene({ actions: [speechAction('a1', '  Hello  ')] });
+    expect(collectSpeechText(s, { trim: true })).toBe('Hello');
+  });
+
+  it('trims each part independently, preserving the join', () => {
+    const s = scene({ actions: [speechAction('a1', ' one '), speechAction('a2', ' two ')] });
+    expect(collectSpeechText(s, { trim: true })).toBe('one\ntwo');
+  });
+
+  it('applies the script options together', () => {
+    const s = scene({
+      actions: [speechAction('a1', '   '), speechAction('a2', '  Hello  ')],
+    });
+    expect(collectSpeechText(s, { keepWhitespaceOnly: false, trim: true })).toBe('Hello');
+  });
+
+  it('keeps internal newlines and blank lines inside a single speech part', () => {
+    const s = scene({ actions: [speechAction('a1', 'Line one.\n\nLine two.')] });
+    expect(collectSpeechText(s)).toBe('Line one.\n\nLine two.');
+  });
+
+  it('joins multiple speech parts with a single newline, not a blank line', () => {
+    const s = scene({ actions: [speechAction('a1', 'A'), speechAction('a2', 'B')] });
+    expect(collectSpeechText(s)).toBe('A\nB');
+  });
+});