diff --git a/api/cache/getLogStores.js b/api/cache/getLogStores.js
index c46166cc0..9230560b3 100644
--- a/api/cache/getLogStores.js
+++ b/api/cache/getLogStores.js
@@ -47,7 +47,7 @@ const namespaces = {
   concurrent: createViolationInstance('concurrent'),
   non_browser: createViolationInstance('non_browser'),
   message_limit: createViolationInstance('message_limit'),
-  token_balance: createViolationInstance('token_balance'),
+  token_balance: createViolationInstance(ViolationTypes.TOKEN_BALANCE),
   registrations: createViolationInstance('registrations'),
   [ViolationTypes.FILE_UPLOAD_LIMIT]: createViolationInstance(ViolationTypes.FILE_UPLOAD_LIMIT),
   [ViolationTypes.ILLEGAL_MODEL_REQUEST]: createViolationInstance(
diff --git a/api/models/Transaction.js b/api/models/Transaction.js
index ba9c10c1c..b88c96d63 100644
--- a/api/models/Transaction.js
+++ b/api/models/Transaction.js
@@ -50,4 +50,23 @@ transactionSchema.statics.create = async function (transactionData) {
   };
 };
 
-module.exports = mongoose.model('Transaction', transactionSchema);
+const Transaction = mongoose.model('Transaction', transactionSchema);
+
+/**
+ * Queries and retrieves transactions based on a given filter.
+ * @async
+ * @function getTransactions
+ * @param {Object} filter - MongoDB filter object to apply when querying transactions.
+ * @returns {Promise<Array>} A promise that resolves to an array of matched transactions.
+ * @throws {Error} Throws an error if querying the database fails.
+ */
+async function getTransactions(filter) {
+  try {
+    return await Transaction.find(filter).lean();
+  } catch (error) {
+    console.error('Error querying transactions:', error);
+    throw error;
+  }
+}
+
+module.exports = { Transaction, getTransactions };
diff --git a/api/models/checkBalance.js b/api/models/checkBalance.js
index 87798166e..5af77bbb1 100644
--- a/api/models/checkBalance.js
+++ b/api/models/checkBalance.js
@@ -1,5 +1,6 @@
+const { ViolationTypes } = require('librechat-data-provider');
+const { logViolation } = require('~/cache');
 const Balance = require('./Balance');
-const { logViolation } = require('../cache');
 /**
  * Checks the balance for a user and determines if they can spend a certain amount.
  * If the user cannot spend the amount, it logs a violation and denies the request.
@@ -25,7 +26,7 @@ const checkBalance = async ({ req, res, txData }) => {
     return true;
   }
 
-  const type = 'token_balance';
+  const type = ViolationTypes.TOKEN_BALANCE;
   const errorMessage = {
     type,
     balance,
diff --git a/api/models/index.js b/api/models/index.js
index f1b51d5ef..bf8819382 100644
--- a/api/models/index.js
+++ b/api/models/index.js
@@ -22,14 +22,12 @@ const Key = require('./Key');
 const User = require('./User');
 const Session = require('./Session');
 const Balance = require('./Balance');
-const Transaction = require('./Transaction');
 
 module.exports = {
   User,
   Key,
   Session,
   Balance,
-  Transaction,
 
   hashPassword,
   updateUser,
diff --git a/api/models/spendTokens.js b/api/models/spendTokens.js
index ac4adeca0..95d46c743 100644
--- a/api/models/spendTokens.js
+++ b/api/models/spendTokens.js
@@ -1,4 +1,4 @@
-const Transaction = require('./Transaction');
+const { Transaction } = require('./Transaction');
 const { logger } = require('~/config');
 
 /**
diff --git a/api/server/routes/assistants/chat.js b/api/server/routes/assistants/chat.js
index 47a5609a8..fd6c5f7bd 100644
--- a/api/server/routes/assistants/chat.js
+++ b/api/server/routes/assistants/chat.js
@@ -1,6 +1,12 @@
 const { v4 } = require('uuid');
 const express = require('express');
-const { EModelEndpoint, Constants, RunStatus, CacheKeys } = require('librechat-data-provider');
+const {
+  Constants,
+  RunStatus,
+  CacheKeys,
+  EModelEndpoint,
+  ViolationTypes,
+} = require('librechat-data-provider');
 const {
   initThread,
   recordUsage,
@@ -11,10 +17,13 @@ const {
 } = require('~/server/services/Threads');
 const { runAssistant, createOnTextProgress } = require('~/server/services/AssistantService');
 const { addTitle, initializeClient } = require('~/server/services/Endpoints/assistants');
-const { sendResponse, sendMessage, sleep } = require('~/server/utils');
+const { sendResponse, sendMessage, sleep, isEnabled, countTokens } = require('~/server/utils');
+const { getTransactions } = require('~/models/Transaction');
 const { createRun } = require('~/server/services/Runs');
+const checkBalance = require('~/models/checkBalance');
 const { getConvo } = require('~/models/Conversation');
 const getLogStores = require('~/cache/getLogStores');
+const { getModelMaxTokens } = require('~/utils');
 const { logger } = require('~/config');
 
 const router = express.Router();
@@ -128,6 +137,8 @@ router.post('/', validateModel, buildEndpointOption, setHeaders, async (req, res
           : ''
       }`;
       return sendResponse(res, messageData, errorMessage);
+    } else if (error?.message?.includes(ViolationTypes.TOKEN_BALANCE)) {
+      return sendResponse(res, messageData, error.message);
     } else {
       logger.error('[/assistants/chat/]', error);
     }
@@ -207,6 +218,38 @@ router.post('/', validateModel, buildEndpointOption, setHeaders, async (req, res
       throw new Error('Missing assistant_id');
     }
 
+    if (isEnabled(process.env.CHECK_BALANCE)) {
+      const transactions =
+        (await getTransactions({
+          user: req.user.id,
+          context: 'message',
+          conversationId,
+        })) ?? [];
+
+      const totalPreviousTokens = Math.abs(
+        transactions.reduce((acc, curr) => acc + curr.rawAmount, 0),
+      );
+
+      // TODO: make promptBuffer a config option; buffer for titles, needs buffer for system instructions
+      const promptBuffer = parentMessageId === Constants.NO_PARENT && !_thread_id ? 200 : 0;
+      // 5 is added for labels
+      let promptTokens = (await countTokens(text + (promptPrefix ?? ''))) + 5;
+      promptTokens += totalPreviousTokens + promptBuffer;
+      // Count tokens up to the current context window
+      promptTokens = Math.min(promptTokens, getModelMaxTokens(model));
+
+      await checkBalance({
+        req,
+        res,
+        txData: {
+          model,
+          user: req.user.id,
+          tokenType: 'prompt',
+          amount: promptTokens,
+        },
+      });
+    }
+
     /** @type {{ openai: OpenAIClient }} */
     const { openai: _openai, client } = await initializeClient({
       req,
diff --git a/client/src/components/Messages/Content/Error.tsx b/client/src/components/Messages/Content/Error.tsx
index 9505d4eba..3d7f4541f 100644
--- a/client/src/components/Messages/Content/Error.tsx
+++ b/client/src/components/Messages/Content/Error.tsx
@@ -1,6 +1,5 @@
 // file deepcode ignore HardcodedNonCryptoSecret: No hardcoded secrets
-
-import React from 'react';
+import { ViolationTypes } from 'librechat-data-provider';
 import type { TOpenAIMessage } from 'librechat-data-provider';
 import { formatJSON, extractJson, isJson } from '~/utils/json';
 import CodeBlock from './CodeBlock';
@@ -15,7 +14,7 @@ type TMessageLimit = {
 };
 
 type TTokenBalance = {
-  type: 'token_balance';
+  type: ViolationTypes;
   balance: number;
   tokenCost: number;
   promptTokens: number;
diff --git a/client/src/components/SidePanel/Switcher.tsx b/client/src/components/SidePanel/Switcher.tsx
index d9cdab852..584389ec8 100644
--- a/client/src/components/SidePanel/Switcher.tsx
+++ b/client/src/components/SidePanel/Switcher.tsx
@@ -52,7 +52,7 @@ export default function Switcher({ isCollapsed }: SwitcherProps) {
   const currentAssistant = assistantMap?.[selectedAssistant ?? ''];
 
   return (
-    <Select defaultValue={selectedAssistant as string | undefined} onValueChange={onSelect}>
+    <Select value={selectedAssistant as string | undefined} onValueChange={onSelect}>
       <SelectTrigger
         className={cn(
           'flex items-center gap-2 [&>span]:line-clamp-1 [&>span]:flex [&>span]:w-full [&>span]:items-center [&>span]:gap-1 [&>span]:truncate [&_svg]:h-4 [&_svg]:w-4 [&_svg]:shrink-0',
diff --git a/client/src/hooks/useNewConvo.ts b/client/src/hooks/useNewConvo.ts
index 58c11f122..52ac45174 100644
--- a/client/src/hooks/useNewConvo.ts
+++ b/client/src/hooks/useNewConvo.ts
@@ -15,7 +15,12 @@ import type {
   TModelsConfig,
   TEndpointsConfig,
 } from 'librechat-data-provider';
-import { buildDefaultConvo, getDefaultEndpoint, getEndpointField } from '~/utils';
+import {
+  buildDefaultConvo,
+  getDefaultEndpoint,
+  getEndpointField,
+  updateLastSelectedModel,
+} from '~/utils';
 import { useDeleteFilesMutation, useListAssistantsQuery } from '~/data-provider';
 import useOriginNavigate from './useOriginNavigate';
 import useSetStorage from './useSetStorage';
@@ -32,7 +37,8 @@ const useNewConvo = (index = 0) => {
   const { data: endpointsConfig = {} as TEndpointsConfig } = useGetEndpointsQuery();
 
   const { data: assistants = [] } = useListAssistantsQuery(defaultOrderQuery, {
-    select: (res) => res.data.map(({ id, name, metadata }) => ({ id, name, metadata })),
+    select: (res) =>
+      res.data.map(({ id, name, metadata, model }) => ({ id, name, metadata, model })),
   });
 
   const { mutateAsync } = useDeleteFilesMutation({
@@ -81,10 +87,30 @@ const useNewConvo = (index = 0) => {
             conversation.endpointType = undefined;
           }
 
-          if (!conversation.assistant_id && defaultEndpoint === EModelEndpoint.assistants) {
-            const assistant_id =
+          const isAssistantEndpoint = defaultEndpoint === EModelEndpoint.assistants;
+
+          if (!conversation.assistant_id && isAssistantEndpoint) {
+            conversation.assistant_id =
               localStorage.getItem(`assistant_id__${index}`) ?? assistants[0]?.id;
-            conversation.assistant_id = assistant_id;
+          }
+
+          if (
+            conversation.assistant_id &&
+            isAssistantEndpoint &&
+            conversation.conversationId === 'new'
+          ) {
+            const assistant = assistants.find(
+              (assistant) => assistant.id === conversation.assistant_id,
+            );
+            conversation.model = assistant?.model;
+            updateLastSelectedModel({
+              endpoint: EModelEndpoint.assistants,
+              model: conversation.model,
+            });
+          }
+
+          if (conversation.assistant_id && !isAssistantEndpoint) {
+            conversation.assistant_id = undefined;
           }
 
           const models = modelsConfig?.[defaultEndpoint] ?? [];
diff --git a/client/src/utils/endpoints.ts b/client/src/utils/endpoints.ts
index e9004bf8a..37ae4fe9e 100644
--- a/client/src/utils/endpoints.ts
+++ b/client/src/utils/endpoints.ts
@@ -56,3 +56,18 @@ export function mapEndpoints(endpointsConfig: TEndpointsConfig) {
     (a, b) => (endpointsConfig?.[a]?.order ?? 0) - (endpointsConfig?.[b]?.order ?? 0),
   );
 }
+
+export function updateLastSelectedModel({
+  endpoint,
+  model,
+}: {
+  endpoint: string;
+  model: string | undefined;
+}) {
+  if (!model) {
+    return;
+  }
+  const lastSelectedModels = JSON.parse(localStorage.getItem('lastSelectedModel') || '{}');
+  lastSelectedModels[endpoint] = model;
+  localStorage.setItem('lastSelectedModel', JSON.stringify(lastSelectedModels));
+}
diff --git a/config/add-balance.js b/config/add-balance.js
index fd86b811f..d525e7df5 100644
--- a/config/add-balance.js
+++ b/config/add-balance.js
@@ -1,7 +1,7 @@
 const path = require('path');
 require('module-alias')({ base: path.resolve(__dirname, '..', 'api') });
 const { askQuestion, silentExit } = require('./helpers');
-const Transaction = require('~/models/Transaction');
+const { Transaction } = require('~/models/Transaction');
 const User = require('~/models/User');
 const connect = require('./connect');
 
diff --git a/packages/data-provider/package.json b/packages/data-provider/package.json
index 887c6732e..b3a0d45b7 100644
--- a/packages/data-provider/package.json
+++ b/packages/data-provider/package.json
@@ -1,6 +1,6 @@
 {
   "name": "librechat-data-provider",
-  "version": "0.4.8",
+  "version": "0.4.9",
   "description": "data services for librechat apps",
   "main": "dist/index.js",
   "module": "dist/index.es.js",
diff --git a/packages/data-provider/src/config.ts b/packages/data-provider/src/config.ts
index be8048666..4badaf04b 100644
--- a/packages/data-provider/src/config.ts
+++ b/packages/data-provider/src/config.ts
@@ -342,11 +342,12 @@ export const modularEndpoints = new Set<EModelEndpoint | string>([
 ]);
 
 export const supportsBalanceCheck = {
+  [EModelEndpoint.custom]: true,
   [EModelEndpoint.openAI]: true,
   [EModelEndpoint.anthropic]: true,
-  [EModelEndpoint.azureOpenAI]: true,
   [EModelEndpoint.gptPlugins]: true,
-  [EModelEndpoint.custom]: true,
+  [EModelEndpoint.assistants]: true,
+  [EModelEndpoint.azureOpenAI]: true,
 };
 
 export const visionModels = ['gpt-4-vision', 'llava-13b', 'gemini-pro-vision', 'claude-3'];
@@ -436,6 +437,10 @@ export enum ViolationTypes {
    * Illegal Model Request (not available).
    */
   ILLEGAL_MODEL_REQUEST = 'illegal_model_request',
+  /**
+   * Token Limit Violation.
+   */
+  TOKEN_BALANCE = 'token_balance',
 }
 
 /**