fix: Bug - Sending files between users doesn't really work

Stream oversized generic attachments to disk instead of silently dropping chunks, avoid loading completed file downloads into renderer memory, and surface a clear error when the browser client cannot receive a file.

Co-authored-by: Cursor <cursoragent@cursor.com>

toju-app/src/app/domains/attachment/domain/logic/attachment.logic.spec.ts

@@ -1,7 +1,9 @@
 import {
   getWatchedAttachmentRoomIdFromUrl,
   isDirectMessageAttachmentRoomId,
-  shouldCopyUploaderMediaToAppData
+  shouldCopyUploaderMediaToAppData,
+  shouldStreamAttachmentReceiveToDisk,
+  canReceiveAttachment
 } from './attachment.logic';
 
 describe('attachment logic', () => {
@@ -44,4 +46,36 @@ describe('attachment logic', () => {
       mime: 'video/mp4'
     }, undefined, true)).toBe(false);
   });
+
+  it('streams oversized generic files to disk when the store supports it', () => {
+    const capabilities = {
+      canStreamToDisk: true,
+      canPersistSize: (bytes: number) => bytes <= 256 * 1024 * 1024
+    };
+
+    expect(shouldStreamAttachmentReceiveToDisk({
+      size: 200 * 1024 * 1024,
+      mime: 'application/zip',
+      filePath: undefined
+    }, capabilities)).toBe(true);
+  });
+
+  it('receives browser-sized files in memory when disk streaming is unavailable', () => {
+    const browserCapabilities = {
+      canStreamToDisk: false,
+      canPersistSize: (bytes: number) => bytes <= 50 * 1024 * 1024
+    };
+
+    expect(canReceiveAttachment({
+      size: 20 * 1024 * 1024,
+      mime: 'application/zip',
+      filePath: undefined
+    }, browserCapabilities)).toBe(true);
+
+    expect(canReceiveAttachment({
+      size: 200 * 1024 * 1024,
+      mime: 'application/zip',
+      filePath: undefined
+    }, browserCapabilities)).toBe(false);
+  });
 });

toju-app/src/app/domains/attachment/domain/logic/attachment.logic.ts

@@ -50,6 +50,49 @@ export function isDirectMessageAttachmentRoomId(roomId: string | null | undefine
   return !!roomId && roomId.startsWith(DIRECT_MESSAGE_ATTACHMENT_STORAGE_PREFIX);
 }
 
+export interface AttachmentReceiveCapabilities {
+  canStreamToDisk: boolean;
+  canPersistSize: (bytes: number) => boolean;
+}
+
+export function shouldStreamAttachmentReceiveToDisk(
+  attachment: Pick<Attachment, 'size' | 'mime' | 'filePath'>,
+  capabilities: AttachmentReceiveCapabilities
+): boolean {
+  if (attachment.filePath?.trim()) {
+    return false;
+  }
+
+  if (!capabilities.canStreamToDisk || !capabilities.canPersistSize(attachment.size)) {
+    return false;
+  }
+
+  if (attachment.size > MAX_AUTO_SAVE_SIZE_BYTES) {
+    return true;
+  }
+
+  return isAttachmentMedia(attachment);
+}
+
+export function canReceiveAttachmentInMemory(
+  attachment: Pick<Attachment, 'size'>,
+  capabilities: AttachmentReceiveCapabilities
+): boolean {
+  if (attachment.size <= MAX_AUTO_SAVE_SIZE_BYTES) {
+    return true;
+  }
+
+  return !capabilities.canStreamToDisk && capabilities.canPersistSize(attachment.size);
+}
+
+export function canReceiveAttachment(
+  attachment: Pick<Attachment, 'size' | 'mime' | 'filePath'>,
+  capabilities: AttachmentReceiveCapabilities
+): boolean {
+  return shouldStreamAttachmentReceiveToDisk(attachment, capabilities)
+    || canReceiveAttachmentInMemory(attachment, capabilities);
+}
+
 function decodeUrlSegment(value: string): string {
   try {
     return decodeURIComponent(value);