🐛(y-provider) destroy Y.Doc instances after each convert request

The Yjs reader and writer in `convertHandler.ts`
were creating `Y.Doc`instances on every request
without calling `.destroy()`, causing a slow heap
leak that could crash the server.

Fixed by wrapping both sites in `try/finally`
blocks that call `ydoc.destroy()`.
Regression tests added to assert `destroy` is
called the expected number of times per request path.

CHANGELOG.md

@@ -13,10 +13,13 @@ and this project adheres to
 ### Changed
 
 - 💄(frontend) improve comments highlights #1961
-- ♿️(frontend) improve BoxButton a11y and native button semantics
-  #2103
+- ♿️(frontend) improve BoxButton a11y and native button semantics #2103
 - ♿️(frontend) improve language picker accessibility #2069
 
+### Fixed
+
+- 🐛(y-provider) destroy Y.Doc instances after each convert request #2129
+
 ## [v4.8.3] - 2026-03-23
 
 ### Changed

src/frontend/servers/y-provider/__tests__/convert.test.ts

@@ -1,6 +1,6 @@
 import { ServerBlockNoteEditor } from '@blocknote/server-util';
 import request from 'supertest';
-import { describe, expect, test, vi } from 'vitest';
+import { afterEach, describe, expect, test, vi } from 'vitest';
 import * as Y from 'yjs';
 
 vi.mock('../src/env', async (importOriginal) => {
@@ -62,7 +62,11 @@ const expectedBlocks = [
 
 console.error = vi.fn();
 
-describe('Server Tests', () => {
+describe('Conversion Testing', () => {
+  afterEach(() => {
+    vi.clearAllMocks();
+  });
+
   test('POST /api/convert with incorrect API key responds with 401', async () => {
     const app = initApp();
 
@@ -170,6 +174,7 @@ describe('Server Tests', () => {
   });
 
   test('POST /api/convert BlockNote to Yjs', async () => {
+    const destroySpy = vi.spyOn(Y.Doc.prototype, 'destroy');
     const app = initApp();
     const editor = ServerBlockNoteEditor.create();
     const blocks = await editor.tryParseMarkdownToBlocks(expectedMarkdown);
@@ -192,6 +197,7 @@ describe('Server Tests', () => {
     const decodedBlocks = editor.yDocToBlocks(ydoc, 'document-store');
 
     expect(decodedBlocks).toStrictEqual(expectedBlocks);
+    expect(destroySpy).toHaveBeenCalledTimes(1);
   });
 
   test('POST /api/convert BlockNote to HTML', async () => {
@@ -253,6 +259,7 @@ describe('Server Tests', () => {
   });
 
   test('POST /api/convert Yjs to JSON', async () => {
+    const destroySpy = vi.spyOn(Y.Doc.prototype, 'destroy');
     const app = initApp();
     const editor = ServerBlockNoteEditor.create();
     const blocks = await editor.tryParseMarkdownToBlocks(expectedMarkdown);
@@ -272,6 +279,7 @@ describe('Server Tests', () => {
     );
     expect(response.body).toBeInstanceOf(Array);
     expect(response.body).toStrictEqual(expectedBlocks);
+    expect(destroySpy).toHaveBeenCalledTimes(1);
   });
 
   test('POST /api/convert Markdown to JSON', async () => {
@@ -293,6 +301,7 @@ describe('Server Tests', () => {
   });
 
   test('POST /api/convert with invalid Yjs content returns 400', async () => {
+    const destroySpy = vi.spyOn(Y.Doc.prototype, 'destroy');
     const app = initApp();
     const response = await request(app)
       .post('/api/convert')
@@ -304,5 +313,6 @@ describe('Server Tests', () => {
 
     expect(response.status).toBe(400);
     expect(response.body).toStrictEqual({ error: 'Invalid content' });
+    expect(destroySpy).toHaveBeenCalledTimes(1);
   });
 });

src/frontend/servers/y-provider/src/handlers/convertHandler.ts

@@ -60,8 +60,12 @@ const readers: InputReader[] = [
     supportedContentTypes: [ContentTypes.YJS, ContentTypes.OctetStream],
     read: async (data) => {
       const ydoc = new Y.Doc();
-      Y.applyUpdate(ydoc, data);
-      return editor.yDocToBlocks(ydoc, 'document-store') as PartialBlock[];
+      try {
+        Y.applyUpdate(ydoc, data);
+        return editor.yDocToBlocks(ydoc, 'document-store') as PartialBlock[];
+      } finally {
+        ydoc.destroy();
+      }
     },
   },
   {
@@ -77,7 +81,14 @@ const writers: OutputWriter[] = [
   },
   {
     supportedContentTypes: [ContentTypes.YJS, ContentTypes.OctetStream],
-    write: async (blocks) => Y.encodeStateAsUpdate(createYDocument(blocks)),
+    write: async (blocks) => {
+      const ydoc = createYDocument(blocks);
+      try {
+        return Y.encodeStateAsUpdate(ydoc);
+      } finally {
+        ydoc.destroy();
+      }
+    },
   },
   {
     supportedContentTypes: [ContentTypes.Markdown, ContentTypes.XMarkdown],