fix: declare w15 namespace when bootstrapping numbering.xml

packages/super-editor/src/core/parts/adapters/numbering-part-descriptor.test.ts

@@ -1,5 +1,19 @@
 import { describe, it, expect } from 'vitest';
-import { syncNumberingToXmlTree } from './numbering-part-descriptor.js';
+import { numberingPartDescriptor, syncNumberingToXmlTree } from './numbering-part-descriptor.js';
+
+describe('numberingPartDescriptor.ensurePart', () => {
+  it('declares xmlns:w15 so w15:* attributes in list definitions are namespace-valid (SD-2252)', () => {
+    const part = numberingPartDescriptor.ensurePart() as {
+      elements: Array<{ attributes: Record<string, string> }>;
+    };
+    const root = part.elements[0];
+
+    expect(root.attributes['xmlns:w']).toBe('http://schemas.openxmlformats.org/wordprocessingml/2006/main');
+    expect(root.attributes['xmlns:w15']).toBe('http://schemas.microsoft.com/office/word/2012/wordml');
+    expect(root.attributes['xmlns:mc']).toBe('http://schemas.openxmlformats.org/markup-compatibility/2006');
+    expect(root.attributes['mc:Ignorable']).toContain('w15');
+  });
+});
 
 describe('syncNumberingToXmlTree', () => {
   it('preserves non-abstract/definition children like w:numPicBullet', () => {

packages/super-editor/src/core/parts/adapters/numbering-part-descriptor.ts

@@ -17,7 +17,19 @@ import { isPartCacheStale, clearPartCacheStale } from '../cache-staleness.js';
 
 const NUMBERING_PART_ID = 'word/numbering.xml' as const;
 
-const NUMBERING_XMLNS = 'http://schemas.openxmlformats.org/wordprocessingml/2006/main';
+/**
+ * Namespace attributes for the `<w:numbering>` root element.
+ *
+ * Includes `xmlns:w15` because base list definitions use
+ * `w15:restartNumberingAfterBreak` — without this declaration the
+ * numbering part is namespace-invalid and Word shows a repair prompt.
+ */
+const NUMBERING_ROOT_ATTRS: Record<string, string> = {
+  'xmlns:w': 'http://schemas.openxmlformats.org/wordprocessingml/2006/main',
+  'xmlns:w15': 'http://schemas.microsoft.com/office/word/2012/wordml',
+  'xmlns:mc': 'http://schemas.openxmlformats.org/markup-compatibility/2006',
+  'mc:Ignorable': 'w15',
+};
 
 // ---------------------------------------------------------------------------
 // Converter shape (minimal interface to avoid importing SuperConverter)
@@ -147,7 +159,7 @@ export const numberingPartDescriptor: PartDescriptor = {
         {
           type: 'element',
           name: 'w:numbering',
-          attributes: { 'xmlns:w': NUMBERING_XMLNS },
+          attributes: { ...NUMBERING_ROOT_ATTRS },
           elements: [],
         },
       ],

tests/doc-api-stories/tests/lists/numbering-metadata-regression.ts

@@ -130,6 +130,15 @@ function countMatches(source: string, pattern: RegExp): number {
   return source.match(pattern)?.length ?? 0;
 }
 
+function getRootStartTag(xml: string, tagName: string): string {
+  const escapedTagName = tagName.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+  const match = xml.match(new RegExp(`<${escapedTagName}\\b[^>]*>`));
+  if (!match) {
+    throw new Error(`Missing root start tag <${tagName}>.`);
+  }
+  return match[0];
+}
+
 describe('document-api story: lists.create numbering metadata regression', () => {
   it('registers numbering metadata when bullet list creation adds numbering to a numbering-less source docx', async () => {
     const resultsDir = path.join(STORIES_ROOT, 'results', 'lists', 'numbering-metadata-regression');
@@ -180,5 +189,21 @@ describe('document-api story: lists.create numbering metadata regression', () =>
       ),
     ).toBe(1);
     expect(countMatches(resultDocumentRels, /Target="numbering\.xml"/g)).toBe(1);
+
+    // SD-2252: every namespace prefix used in the numbering part must be
+    // declared on the root element, otherwise Word flags the file as
+    // unreadable. Check the actual <w:numbering ...> start tag so we do not
+    // false-pass on an xmlns declaration that appears later or in a narrower scope.
+    const numberingRootStartTag = getRootStartTag(resultNumbering, 'w:numbering');
+    const usedPrefixes = new Set([...resultNumbering.matchAll(/(?:^|[\s<])(\w+):/g)].map((m) => m[1]));
+    // xml and xmlns are built-in prefixes that never need an explicit declaration.
+    usedPrefixes.delete('xml');
+    usedPrefixes.delete('xmlns');
+
+    for (const prefix of usedPrefixes) {
+      expect(numberingRootStartTag, `missing xmlns:${prefix} declaration on <w:numbering>`).toMatch(
+        new RegExp(`xmlns:${prefix}=`),
+      );
+    }
   });
 });