fix: use DEFLATE compression for docx export instead of STORE

packages/super-editor/src/core/DocxZipper.js

@@ -262,7 +262,7 @@ class DocxZipper {
     return zip;
   }
 
-  async updateZip({ docx, updatedDocs, originalDocxFile, media, fonts, isHeadless }) {
+  async updateZip({ docx, updatedDocs, originalDocxFile, media, fonts, isHeadless, compression = 'DEFLATE' }) {
     // We use a different re-zip process if we have the original docx vs the docx xml metadata
     let zip;
 
@@ -274,7 +274,11 @@ class DocxZipper {
 
     // If we are headless we don't have 'blob' support, so export as 'nodebuffer'
     const exportType = isHeadless ? 'nodebuffer' : 'blob';
-    return await zip.generateAsync({ type: exportType });
+    return await zip.generateAsync({
+      type: exportType,
+      compression,
+      compressionOptions: compression === 'DEFLATE' ? { level: 6 } : undefined,
+    });
   }
 
   /**

packages/super-editor/src/core/DocxZipper.test.js

@@ -109,6 +109,97 @@ describe('DocxZipper - UTF-16 XML handling', () => {
   });
 });
 
+describe('DocxZipper - updateZip compression', () => {
+  it('uses DEFLATE compression by default', async () => {
+    const zipper = new DocxZipper();
+
+    const contentTypes = `<?xml version="1.0" encoding="UTF-8"?>
+      <Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
+        <Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
+        <Default Extension="xml" ContentType="application/xml"/>
+        <Override PartName="/word/document.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.document.main+xml"/>
+      </Types>`;
+
+    const documentXml = `<?xml version="1.0" encoding="UTF-8"?>
+      <w:document xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main">
+        <w:body><w:p><w:r><w:t>${'Hello world. '.repeat(100)}</w:t></w:r></w:p></w:body>
+      </w:document>`;
+
+    const docx = [
+      { name: '[Content_Types].xml', content: contentTypes },
+      { name: 'word/document.xml', content: documentXml },
+    ];
+
+    const result = await zipper.updateZip({
+      docx,
+      updatedDocs: {},
+      media: {},
+      fonts: {},
+      isHeadless: true,
+    });
+
+    // Verify the output is compressed by checking DEFLATE produces smaller output than STORE
+    const storeResult = await new DocxZipper().updateZip({
+      docx,
+      updatedDocs: {},
+      media: {},
+      fonts: {},
+      isHeadless: true,
+      compression: 'STORE',
+    });
+
+    expect(result.length).toBeLessThan(storeResult.length);
+
+    // Verify the compressed output is a valid zip that can be read back
+    const readBack = await new JSZip().loadAsync(result);
+    const docXml = await readBack.file('word/document.xml').async('string');
+    expect(docXml).toContain('Hello world.');
+  });
+
+  it('respects STORE compression when explicitly requested', async () => {
+    const zipper = new DocxZipper();
+
+    const contentTypes = `<?xml version="1.0" encoding="UTF-8"?>
+      <Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
+        <Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
+        <Default Extension="xml" ContentType="application/xml"/>
+        <Override PartName="/word/document.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.document.main+xml"/>
+      </Types>`;
+
+    const documentXml = `<?xml version="1.0" encoding="UTF-8"?>
+      <w:document xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main">
+        <w:body><w:p><w:r><w:t>${'Hello world. '.repeat(100)}</w:t></w:r></w:p></w:body>
+      </w:document>`;
+
+    const docx = [
+      { name: '[Content_Types].xml', content: contentTypes },
+      { name: 'word/document.xml', content: documentXml },
+    ];
+
+    const result = await zipper.updateZip({
+      docx,
+      updatedDocs: {},
+      media: {},
+      fonts: {},
+      isHeadless: true,
+      compression: 'STORE',
+    });
+
+    // STORE should produce output roughly the size of the uncompressed content
+    // (plus ZIP overhead), so it should be larger than DEFLATE
+    const deflateResult = await new DocxZipper().updateZip({
+      docx,
+      updatedDocs: {},
+      media: {},
+      fonts: {},
+      isHeadless: true,
+      compression: 'DEFLATE',
+    });
+
+    expect(result.length).toBeGreaterThan(deflateResult.length);
+  });
+});
+
 describe('DocxZipper - updateContentTypes', () => {
   it('adds header/footer overrides for newly added parts', async () => {
     const zipper = new DocxZipper();

packages/super-editor/src/core/Editor.ts

@@ -138,6 +138,9 @@ export interface SaveOptions {
 
   /** Highlight color for fields */
   fieldsHighlightColor?: string | null;
+
+  /** ZIP compression method for docx export. Defaults to 'DEFLATE'. Use 'STORE' for faster exports without compression. */
+  compression?: 'DEFLATE' | 'STORE';
 }
 
 /**
@@ -2484,6 +2487,7 @@ export class Editor extends EventEmitter<EditorEventMap> {
     comments,
     getUpdatedDocs = false,
     fieldsHighlightColor = null,
+    compression,
   }: {
     isFinalDoc?: boolean;
     commentsType?: string;
@@ -2492,6 +2496,7 @@ export class Editor extends EventEmitter<EditorEventMap> {
     comments?: Comment[];
     getUpdatedDocs?: boolean;
     fieldsHighlightColor?: string | null;
+    compression?: 'DEFLATE' | 'STORE';
   } = {}): Promise<Blob | ArrayBuffer | Buffer | Record<string, string> | ProseMirrorJSON | string | undefined> {
     try {
       // Use provided comments, or fall back to imported comments from converter
@@ -2623,6 +2628,7 @@ export class Editor extends EventEmitter<EditorEventMap> {
         media,
         fonts: this.options.fonts,
         isHeadless: this.options.isHeadless,
+        compression,
       });
 
       return result;
@@ -2893,6 +2899,7 @@ export class Editor extends EventEmitter<EditorEventMap> {
       commentsType: options?.commentsType,
       comments: options?.comments,
       fieldsHighlightColor: options?.fieldsHighlightColor,
+      compression: options?.compression,
     });
 
     return result as Blob | Buffer;