diff --git a/client/src/hooks/useTokenUsage.ts b/client/src/hooks/useTokenUsage.ts
index 3141c9c454..06b306bc49 100644
--- a/client/src/hooks/useTokenUsage.ts
+++ b/client/src/hooks/useTokenUsage.ts
@@ -1,10 +1,10 @@
 import { useEffect, useMemo } from 'react';
 import { useParams } from 'react-router-dom';
 import { useSetAtom, useAtomValue } from 'jotai';
-import { getModelMaxTokens } from 'librechat-data-provider';
+import { getModelMaxTokens, isAgentsEndpoint } from 'librechat-data-provider';
 import type { TMessage } from 'librechat-data-provider';
 import { tokenUsageAtom, type TokenUsage } from '~/store/tokenUsage';
-import { useGetMessagesByConvoId } from '~/data-provider';
+import { useGetMessagesByConvoId, useGetAgentByIdQuery } from '~/data-provider';
 import { useChatContext } from '~/Providers';
 
 /**
@@ -17,27 +17,47 @@ export function useTokenUsageComputation() {
   const setTokenUsage = useSetAtom(tokenUsageAtom);
   const { conversationId: paramId } = useParams();
 
-  // Determine the query key to use - same logic as useChatHelpers
-  const queryParam = paramId === 'new' ? paramId : conversationId || paramId || '';
+  // Determine if we need to fetch agent details for token limits
+  const endpoint = conversation?.endpoint ?? '';
+  const isAgent = isAgentsEndpoint(endpoint);
+  const agentId = isAgent ? conversation?.agent_id : null;
 
-  // Use the query hook to get reactive messages
-  // Subscribe to both the paramId-based key and conversationId-based key
-  const { data: messages } = useGetMessagesByConvoId(queryParam, {
-    enabled: !!queryParam,
+  // Fetch full agent details (includes model and provider) when using agents endpoint
+  const { data: agent } = useGetAgentByIdQuery(agentId, {
+    enabled: !!agentId,
   });
 
-  // Also subscribe to the actual conversationId if different from queryParam
-  // This ensures we get updates when conversation transitions from 'new' to actual ID
-  const { data: messagesById } = useGetMessagesByConvoId(conversationId, {
-    enabled: !!conversationId && conversationId !== 'new' && conversationId !== queryParam,
+  /**
+   * Determine the effective conversation ID for querying messages.
+   *
+   * Priority logic:
+   * 1. If URL param is 'new' -> use 'new' (landing page, no conversation yet)
+   * 2. If conversation has actual ID -> use it (active conversation)
+   * 3. Fallback to URL param (handles direct navigation to /c/:id)
+   *
+   * This ensures we always query the correct messages cache key and avoids
+   * dual subscriptions that would cause duplicate reactivity and API calls.
+   */
+  const effectiveConversationId = useMemo(() => {
+    if (paramId === 'new') {
+      return 'new';
+    }
+    return conversationId || paramId || '';
+  }, [paramId, conversationId]);
+
+  /**
+   * Single subscription to messages for the effective conversation ID.
+   * React Query caches messages by [QueryKeys.messages, id], so we'll
+   * automatically get updates when:
+   * - New messages are added via setMessages() in useChatHelpers
+   * - Conversation transitions from 'new' to actual ID (cache is synced in setMessages)
+   * - Messages are fetched from the server
+   */
+  const { data: messages } = useGetMessagesByConvoId(effectiveConversationId, {
+    enabled: !!effectiveConversationId,
   });
 
-  // Use whichever has more messages (handles transition from new -> actual ID)
-  const effectiveMessages = useMemo(() => {
-    const msgArray = messages ?? [];
-    const msgByIdArray = messagesById ?? [];
-    return msgByIdArray.length > msgArray.length ? msgByIdArray : msgArray;
-  }, [messages, messagesById]);
+  const effectiveMessages = useMemo<TMessage[]>(() => messages ?? [], [messages]);
 
   // Compute token usage whenever messages change
   const tokenData = useMemo(() => {
@@ -45,7 +65,7 @@ export function useTokenUsageComputation() {
     let outputTokens = 0;
 
     if (effectiveMessages && Array.isArray(effectiveMessages)) {
-      for (const msg of effectiveMessages as TMessage[]) {
+      for (const msg of effectiveMessages) {
         const count = msg.tokenCount ?? 0;
         if (msg.isCreatedByUser) {
           inputTokens += count;
@@ -59,11 +79,22 @@ export function useTokenUsageComputation() {
     let maxContext: number | null = conversation?.maxContextTokens ?? null;
 
     // If no explicit maxContextTokens, try to look up model default
-    if (maxContext === null && conversation?.model) {
-      const endpoint = conversation.endpointType ?? conversation.endpoint ?? '';
-      const modelDefault = getModelMaxTokens(conversation.model, endpoint);
-      if (modelDefault !== undefined) {
-        maxContext = modelDefault;
+    if (maxContext === null) {
+      // For agents endpoint, get the actual model from the fetched agent
+      if (isAgent && agent?.model) {
+        // Use agent's provider, or fall back to 'agents' endpoint for lookup
+        const provider = agent.provider ?? endpoint;
+        const modelDefault = getModelMaxTokens(agent.model, provider);
+        if (modelDefault !== undefined) {
+          maxContext = modelDefault;
+        }
+      } else if (conversation?.model) {
+        // For other endpoints, use conversation model directly
+        const effectiveEndpoint = conversation?.endpointType ?? endpoint;
+        const modelDefault = getModelMaxTokens(conversation.model, effectiveEndpoint);
+        if (modelDefault !== undefined) {
+          maxContext = modelDefault;
+        }
       }
     }
 
@@ -76,8 +107,10 @@ export function useTokenUsageComputation() {
     effectiveMessages,
     conversation?.maxContextTokens,
     conversation?.model,
-    conversation?.endpoint,
     conversation?.endpointType,
+    isAgent,
+    agent,
+    endpoint,
   ]);
 
   // Update the atom when computed values change