fix: resolve additional Meilisearch plugin bugs found in review

Address review findings from PR #12542:

- Fix deleteObjectFromMeili using MongoDB _id instead of the Meilisearch
  primary key (conversationId/messageId), causing post-remove cleanup to
  silently no-op and leave orphaned documents in the index.

- Pass options.primaryKey explicitly to createMeiliMongooseModel factory
  instead of deriving it from attributesToIndex[0] (schema field order),
  eliminating a fragile implicit contract.

- Fix updateObjectToMeili skipping preprocessObjectForIndex, which meant
  updates bypassed content array-to-text conversion and conversationId
  pipe character escaping.

- Change collection.updateMany to collection.updateOne in addObjectToMeili
  since _id is unique (semantic correctness).

- Add primaryKey to validateOptions required keys.

- Strengthen test assertions to verify { primaryKey } argument is passed
  to addDocuments, addDocumentsInBatches, and updateDocuments. Add tests
  for the update path including preprocessObjectForIndex pipe escaping.

packages/data-schemas/src/models/plugins/mongoMeili.spec.ts

@@ -73,7 +73,10 @@ describe('Meilisearch Mongoose plugin', () => {
       title: 'Test Conversation',
       endpoint: EModelEndpoint.openAI,
     });
-    expect(mockAddDocuments).toHaveBeenCalled();
+    expect(mockAddDocuments).toHaveBeenCalledWith(
+      [expect.objectContaining({ conversationId: expect.anything() })],
+      { primaryKey: 'conversationId' },
+    );
   });
 
   test('saving conversation indexes with expiredAt=null w/ meilisearch', async () => {
@@ -105,7 +108,10 @@ describe('Meilisearch Mongoose plugin', () => {
       user: new mongoose.Types.ObjectId(),
       isCreatedByUser: true,
     });
-    expect(mockAddDocuments).toHaveBeenCalled();
+    expect(mockAddDocuments).toHaveBeenCalledWith(
+      [expect.objectContaining({ messageId: expect.anything() })],
+      { primaryKey: 'messageId' },
+    );
   });
 
   test('saving messages with expiredAt=null indexes w/ meilisearch', async () => {
@@ -130,6 +136,47 @@ describe('Meilisearch Mongoose plugin', () => {
     expect(mockAddDocuments).not.toHaveBeenCalled();
   });
 
+  test('updating an indexed conversation calls updateDocuments with primaryKey', async () => {
+    const conversationModel = createConversationModel(mongoose);
+    const convo = await conversationModel.create({
+      conversationId: new mongoose.Types.ObjectId().toString(),
+      user: new mongoose.Types.ObjectId(),
+      title: 'Original Title',
+      endpoint: EModelEndpoint.openAI,
+    });
+    mockUpdateDocuments.mockClear();
+
+    convo._meiliIndex = true;
+    convo.title = 'Updated Title';
+    await convo.save();
+
+    expect(mockUpdateDocuments).toHaveBeenCalledWith(
+      [expect.objectContaining({ conversationId: expect.anything() })],
+      { primaryKey: 'conversationId' },
+    );
+  });
+
+  test('updateDocuments receives preprocessed data with primaryKey', async () => {
+    const conversationModel = createConversationModel(mongoose);
+    const conversationId = 'abc|def|ghi';
+    const convo = await conversationModel.create({
+      conversationId,
+      user: new mongoose.Types.ObjectId(),
+      title: 'Pipe Test',
+      endpoint: EModelEndpoint.openAI,
+    });
+    mockUpdateDocuments.mockClear();
+
+    convo._meiliIndex = true;
+    convo.title = 'Updated Pipe Test';
+    await convo.save();
+
+    expect(mockUpdateDocuments).toHaveBeenCalledWith(
+      [expect.objectContaining({ conversationId: 'abc--def--ghi' })],
+      { primaryKey: 'conversationId' },
+    );
+  });
+
   test('sync w/ meili does not include TTL documents', async () => {
     const conversationModel = createConversationModel(mongoose) as SchemaWithMeiliMethods;
     await conversationModel.create({
@@ -299,8 +346,10 @@ describe('Meilisearch Mongoose plugin', () => {
       // Run sync which should call processSyncBatch internally
       await conversationModel.syncWithMeili();
 
-      // Verify addDocumentsInBatches was called (new batch method)
-      expect(mockAddDocumentsInBatches).toHaveBeenCalled();
+      // Verify addDocumentsInBatches was called with explicit primaryKey
+      expect(mockAddDocumentsInBatches).toHaveBeenCalledWith(expect.any(Array), undefined, {
+        primaryKey: 'conversationId',
+      });
     });
 
     test('addObjectToMeili retries on failure', async () => {

packages/data-schemas/src/models/plugins/mongoMeili.ts

@@ -94,7 +94,7 @@ const getSyncConfig = () => ({
  * Validates the required options for configuring the mongoMeili plugin.
  */
 const validateOptions = (options: Partial<MongoMeiliOptions>): void => {
-  const requiredKeys: (keyof MongoMeiliOptions)[] = ['host', 'apiKey', 'indexName'];
+  const requiredKeys: (keyof MongoMeiliOptions)[] = ['host', 'apiKey', 'indexName', 'primaryKey'];
   requiredKeys.forEach((key) => {
     if (!options[key]) {
       throw new Error(`Missing mongoMeili Option: ${key}`);
@@ -136,13 +136,14 @@ const processBatch = async <T>(
 const createMeiliMongooseModel = ({
   index,
   attributesToIndex,
+  primaryKey,
   syncOptions,
 }: {
   index: Index<MeiliIndexable>;
   attributesToIndex: string[];
+  primaryKey: string;
   syncOptions: { batchSize: number; delayMs: number };
 }) => {
-  const primaryKey = attributesToIndex[0];
   const syncConfig = { ...getSyncConfig(), ...syncOptions };
 
   class MeiliMongooseModel {
@@ -436,11 +437,10 @@ const createMeiliMongooseModel = ({
       }
 
       try {
-        const Model = this.constructor as Model<DocumentWithMeiliIndex>;
-        await Model.updateMany(
+        // eslint-disable-next-line no-restricted-syntax -- _meiliIndex is an internal bookkeeping flag, not tenant-scoped data
+        await this.collection.updateOne(
           { _id: this._id as Types.ObjectId },
           { $set: { _meiliIndex: true } },
-          { timestamps: false },
         );
       } catch (error) {
         logger.error('[addObjectToMeili] Error updating _meiliIndex field:', error);
@@ -458,9 +458,7 @@ const createMeiliMongooseModel = ({
       next: CallbackWithoutResultAndOptionalError,
     ): Promise<void> {
       try {
-        const object = _.omitBy(_.pick(this.toJSON(), attributesToIndex), (v, k) =>
-          k.startsWith('$'),
-        );
+        const object = this.preprocessObjectForIndex!();
         await index.updateDocuments([object], { primaryKey });
         next();
       } catch (error) {
@@ -479,7 +477,7 @@ const createMeiliMongooseModel = ({
       next: CallbackWithoutResultAndOptionalError,
     ): Promise<void> {
       try {
-        await index.deleteDocument(this._id as string);
+        await index.deleteDocument(String(this[primaryKey as keyof DocumentWithMeiliIndex]));
         next();
       } catch (error) {
         logger.error('[deleteObjectFromMeili] Error deleting document from Meili:', error);
@@ -645,7 +643,7 @@ export default function mongoMeili(schema: Schema, options: MongoMeiliOptions):
     logger.debug(`[mongoMeili] Added 'user' field to ${indexName} index attributes`);
   }
 
-  schema.loadClass(createMeiliMongooseModel({ index, attributesToIndex, syncOptions }));
+  schema.loadClass(createMeiliMongooseModel({ index, attributesToIndex, primaryKey, syncOptions }));
 
   // Register Mongoose hooks
   schema.post('save', function (doc: DocumentWithMeiliIndex, next) {