🧵 fix: Reject Preliminary Parent Follow-Ups (#13619)

* fix: Reject preliminary parent follow-ups

* chore: Sort frontend imports

* fix: Narrow preliminary parent detection

* fix: Preserve refused submit state

* fix: Propagate refused submit result

packages/api/src/utils/message.spec.ts

@@ -4,6 +4,8 @@ import {
   sanitizeFileForTransmit,
   buildMessageFiles,
   getThreadData,
+  isPreliminaryMessageId,
+  isUnpersistedPreliminaryParent,
 } from './message';
 
 /** Cast to string for type compatibility with ThreadMessage */
@@ -130,6 +132,55 @@ describe('sanitizeMessageForTransmit', () => {
   });
 });
 
+describe('isUnpersistedPreliminaryParent', () => {
+  it('returns false without querying for non-preliminary parent ids', async () => {
+    const getMessages = jest.fn();
+
+    await expect(
+      isUnpersistedPreliminaryParent({
+        userId: 'user-123',
+        conversationId: 'conversation-123',
+        parentMessageId: 'persisted-response',
+        getMessages,
+      }),
+    ).resolves.toBe(false);
+
+    expect(isPreliminaryMessageId('persisted-response')).toBe(false);
+    expect(getMessages).not.toHaveBeenCalled();
+  });
+
+  it('returns true when the underscore-suffixed parent is not persisted', async () => {
+    const getMessages = jest.fn().mockResolvedValue([]);
+
+    await expect(
+      isUnpersistedPreliminaryParent({
+        userId: 'user-123',
+        conversationId: 'conversation-123',
+        parentMessageId: 'pending-response_',
+        getMessages,
+      }),
+    ).resolves.toBe(true);
+
+    expect(getMessages).toHaveBeenCalledWith(
+      { user: 'user-123', messageId: 'pending-response_', conversationId: 'conversation-123' },
+      '_id',
+    );
+  });
+
+  it('returns false when the underscore-suffixed parent is already persisted', async () => {
+    const getMessages = jest.fn().mockResolvedValue([{ _id: 'persisted-parent' }]);
+
+    await expect(
+      isUnpersistedPreliminaryParent({
+        userId: 'user-123',
+        conversationId: 'conversation-123',
+        parentMessageId: 'persisted-response_',
+        getMessages,
+      }),
+    ).resolves.toBe(false);
+  });
+});
+
 describe('buildMessageFiles', () => {
   const baseAttachment = {
     file_id: 'file-1',

packages/api/src/utils/message.ts

@@ -4,6 +4,11 @@ import type { TFile, TMessage } from 'librechat-data-provider';
 /** Minimal shape for request file entries (from `req.body.files`) */
 type RequestFile = { file_id?: string };
 
+type GetMessagesByParentId = (
+  filter: { user: string; messageId: string; conversationId?: string },
+  select: '_id',
+) => Promise<unknown[]>;
+
 /** Fields to strip from files before client transmission */
 const FILE_STRIP_FIELDS = ['text', '_id', '__v'] as const;
 
@@ -92,6 +97,37 @@ export function sanitizeMessageForTransmit<T extends Partial<TMessage>>(
   return sanitized;
 }
 
+export function isPreliminaryMessageId(messageId: unknown): messageId is string {
+  return typeof messageId === 'string' && messageId.endsWith('_');
+}
+
+export async function isUnpersistedPreliminaryParent({
+  userId,
+  conversationId,
+  parentMessageId,
+  getMessages,
+}: {
+  userId: string;
+  conversationId?: string | null;
+  parentMessageId?: string | null;
+  getMessages: GetMessagesByParentId;
+}): Promise<boolean> {
+  if (!isPreliminaryMessageId(parentMessageId)) {
+    return false;
+  }
+
+  const filter: { user: string; messageId: string; conversationId?: string } = {
+    user: userId,
+    messageId: parentMessageId,
+  };
+  if (conversationId && conversationId !== Constants.NEW_CONVO) {
+    filter.conversationId = conversationId;
+  }
+
+  const messages = await getMessages(filter, '_id');
+  return messages.length === 0;
+}
+
 /** Minimal message shape for thread traversal.
  *
  * Both `files` and `attachments` carry `file_id` references, but they