fix(server): make Yjs sole writer of Document.content

client/src/hooks/use-document.ts

@@ -51,11 +51,15 @@ export function useDocument(id?: string) {
   }, [id]);
 
   const handleSave = useCallback(async () => {
-    if (!id) return;
+    if (!id || !editedDoc) return;
     try {
       setSaving(true);
       setError(null);
-      await api.put(`/document/${id}`, editedDoc);
+      // Content is owned by Yjs sync; REST persists metadata only (issue #47).
+      await api.put(`/document/${id}`, {
+        title: editedDoc.title,
+        isPublic: editedDoc.isPublic,
+      });
       setDoc(editedDoc);
     } catch (err) {
       console.error('Failed to save document:', err);

server/src/controllers/document.controller.ts

@@ -10,22 +10,23 @@ import { getClientInfo } from '@/utils/getClientInfo';
 export const createDoc = asyncErrorWrapper(async (req: AuthenticatedRequest, res: Response) => {
   const clientInfo = getClientInfo(req);
   const userId = req.user?.userId;
-  const { title, content = '', isPublic = false } = req.body;
+  const { title, isPublic = false } = req.body;
 
   logger.debug('Document creation attempt', {
     action: 'CREATE_DOCUMENT_ATTEMPT',
     ...clientInfo,
     userId,
     title,
     isPublic,
-    contentLength: content.length,
   });
 
   try {
+    // `content` starts empty and is owned by Yjs sync afterwards (issue #47);
+    // accepting it here would store text no reader ever sees.
     const newDoc = await prisma.document.create({
       data: {
         title,
-        content,
+        content: '',
         isPublic,
         authorId: req.user?.userId,
       },
@@ -190,18 +191,7 @@ export const updateDoc = asyncErrorWrapper(async (req: AuthenticatedRequest, res
   const clientInfo = getClientInfo(req);
   const userId = req.user?.userId;
   const documentId = req.params.id;
-  const { title, content, isPublic } = req.body;
-
-  // logger.info('Document update attempt', {
-  //   action: 'UPDATE_DOCUMENT_ATTEMPT',
-  //   ...clientInfo,
-  //   userId,
-  //   documentId,
-  //   title,
-  //   isPublic,
-  //   contentLength: content?.length,
-  // });
-
+  const { title, isPublic } = req.body;
   try {
     const doc = await prisma.document.findFirst({
       where: { id: documentId },
@@ -227,11 +217,12 @@ export const updateDoc = asyncErrorWrapper(async (req: AuthenticatedRequest, res
       return;
     }
 
+    // `content` is intentionally not writable here: it is a mirror of the
+    // Yjs document state maintained by dbPersistence.store (issue #47).
     const updatedDoc = await prisma.document.update({
       where: { id: doc.id },
-      data: { title, content, isPublic },
+      data: { title, isPublic },
     });
-
     // logger.info('Document updated successfully', {
     //   action: 'UPDATE_DOCUMENT_SUCCESS',
     //   ...clientInfo,

server/src/lib/dbPersistence.ts

@@ -54,35 +54,38 @@ export const dbPersistence = new Database({
       });
 
       if (existing) {
-        await prisma.yjsDocumentState.update({
-          where: { documentId: id },
-          data: {
-            state: Buffer.from(state),
-            version: { increment: 1 },
-          },
-        });
-
-        await prisma.document.update({
-          where: { id: id },
-          data: { content: plainText },
-        });
+        // Snapshot and its plaintext mirror must stay consistent: write both atomically.
+        await prisma.$transaction([
+          prisma.yjsDocumentState.update({
+            where: { documentId: id },
+            data: {
+              state: Buffer.from(state),
+              version: { increment: 1 },
+            },
+          }),
+          prisma.document.update({
+            where: { id: id },
+            data: { content: plainText },
+          }),
+        ]);
       } else {
         const documentExists = await prisma.document.findFirst({
           where: { id: id },
         });
 
         if (documentExists) {
-          await prisma.yjsDocumentState.create({
-            data: {
-              documentId: documentExists.id,
-              state: Buffer.from(state),
-            },
-          });
-
-          await prisma.document.update({
-            where: { id: documentExists.id },
-            data: { content: plainText },
-          });
+          await prisma.$transaction([
+            prisma.yjsDocumentState.create({
+              data: {
+                documentId: documentExists.id,
+                state: Buffer.from(state),
+              },
+            }),
+            prisma.document.update({
+              where: { id: documentExists.id },
+              data: { content: plainText },
+            }),
+          ]);
         } else {
           logger.warn(`No Document found for ID prefix: ${documentName}`, {
             action: 'DB_STORE_DOC_NOT_FOUND',

server/test/document.test.ts

@@ -95,6 +95,24 @@ describe('Document Routes', () => {
     expect(res.body.title).toBe('Updated Title');
   });
 
+  it('should not overwrite document content via REST update (Yjs is the source of truth)', async () => {
+    const created = await prisma.document.create({
+      data: { title: 'Synced Doc', content: 'yjs-derived-content', authorId: userId },
+    });
+
+    const res = await request(app)
+      .put(`/api/document/${created.id}`)
+      .set('Authorization', `Bearer ${token}`)
+      .send({ title: 'Renamed', content: 'rest-overwrite-attempt' });
+
+    expect(res.status).toBe(StatusCodes.OK);
+    expect(res.body.title).toBe('Renamed');
+    expect(res.body.content).toBe('yjs-derived-content');
+
+    const doc = await prisma.document.findUniqueOrThrow({ where: { id: created.id } });
+    expect(doc.content).toBe('yjs-derived-content');
+  });
+
   it('should delete a document', async () => {
     const created = await prisma.document.create({
       data: {