🔒 fix: Exclude Unnecessary fields from Conversation $unset (#12501)

`BaseClient.js` iterates existing conversation keys to build `unsetFields`
for removal when `endpointOptions` doesn't include them. When tenant
isolation stamps `tenantId` on the document, it gets swept into `$unset`,
triggering `assertNoTenantIdMutation`. Adding `tenantId` to `excludedKeys`
prevents this — it's a system field, not an endpoint option.

packages/data-provider/src/config.spec.ts

@@ -1,7 +1,7 @@
 import type { TEndpointsConfig } from './types';
 import { EModelEndpoint, isDocumentSupportedProvider } from './schemas';
 import { getEndpointFileConfig, mergeFileConfig } from './file-config';
-import { resolveEndpointType } from './config';
+import { resolveEndpointType, excludedKeys } from './config';
 
 const endpointsConfig: TEndpointsConfig = {
   [EModelEndpoint.openAI]: { userProvide: false, order: 0 },
@@ -13,6 +13,15 @@ const endpointsConfig: TEndpointsConfig = {
   Gemini: { type: EModelEndpoint.custom, userProvide: false, order: 9999 },
 };
 
+describe('excludedKeys', () => {
+  it.each(['_id', 'user', 'conversationId', '__v', 'tenantId'])(
+    'excludes system field "%s"',
+    (field) => {
+      expect(excludedKeys.has(field)).toBe(true);
+    },
+  );
+});
+
 describe('resolveEndpointType', () => {
   describe('non-agents endpoints', () => {
     it('returns the config type for a custom endpoint', () => {

packages/data-provider/src/config.ts

@@ -48,6 +48,7 @@ export const excludedKeys = new Set([
   'isArchived',
   'tags',
   'user',
+  'tenantId',
   '__v',
   '_id',
   'tools',