diff --git a/api/app/clients/tools/util/fileSearch.js b/api/app/clients/tools/util/fileSearch.js
index a9faf71c54..be7589a826 100644
--- a/api/app/clients/tools/util/fileSearch.js
+++ b/api/app/clients/tools/util/fileSearch.js
@@ -25,7 +25,7 @@ const fileSearchJsonSchema = {
  * @param {Agent['tool_resources']} options.tool_resources
  * @param {string} [options.agentId] - The agent ID for file access control
  * @returns {Promise<{
- *   files: Array<{ file_id: string; filename: string }>,
+ *   files: Array<{ file_id: string; filename: string; fromAgent: boolean }>,
  *   toolContext: string
  * }>}
  */
@@ -70,6 +70,7 @@ const primeFiles = async (options) => {
     files.push({
       file_id: file.file_id,
       filename: file.filename,
+      fromAgent: agentResourceIds.has(file.file_id),
     });
   }
 
@@ -80,7 +81,7 @@ const primeFiles = async (options) => {
  *
  * @param {Object} options
  * @param {string} options.userId
- * @param {Array<{ file_id: string; filename: string }>} options.files
+ * @param {Array<{ file_id: string; filename: string; fromAgent?: boolean }>} options.files
  * @param {string} [options.entity_id]
  * @param {boolean} [options.fileCitations=false] - Whether to include citation instructions
  * @returns
@@ -97,7 +98,7 @@ const createFileSearchTool = async ({ userId, files, entity_id, fileCitations =
       }
 
       /**
-       * @param {import('librechat-data-provider').TFile} file
+       * @param {import('librechat-data-provider').TFile & { fromAgent?: boolean }} file
        * @returns {{ file_id: string, query: string, k: number, entity_id?: string }}
        */
       const createQueryBody = (file) => {
@@ -106,7 +107,14 @@ const createFileSearchTool = async ({ userId, files, entity_id, fileCitations =
           query,
           k: 5,
         };
-        if (!entity_id) {
+        // User-attached files are embedded under the user id (no entity);
+        // only agent knowledge-base files carry the agent's entity_id.
+        // Sending entity_id for user attachments makes the RAG API's entity
+        // filter return no results for them. When files are provided by
+        // primeFiles, fromAgent is always set; for callers that pass files
+        // directly without the flag, the safe default is unscoped (no
+        // entity_id).
+        if (!entity_id || file.fromAgent !== true) {
           return body;
         }
         body.entity_id = entity_id;
diff --git a/api/test/app/clients/tools/util/fileSearch.test.js b/api/test/app/clients/tools/util/fileSearch.test.js
index 782e48f720..d9b5edb64c 100644
--- a/api/test/app/clients/tools/util/fileSearch.test.js
+++ b/api/test/app/clients/tools/util/fileSearch.test.js
@@ -230,3 +230,63 @@ describe('fileSearch.js - tuple return validation', () => {
     });
   });
 });
+
+describe('entity_id scoping by file origin', () => {
+  const ORIGINAL_RAG_API_URL = process.env.RAG_API_URL;
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    process.env.RAG_API_URL = 'http://localhost:8000';
+    generateShortLivedToken.mockReturnValue('mock-jwt-token');
+    axios.post.mockResolvedValue({ data: [] });
+  });
+
+  afterEach(() => {
+    if (ORIGINAL_RAG_API_URL === undefined) {
+      delete process.env.RAG_API_URL;
+    } else {
+      process.env.RAG_API_URL = ORIGINAL_RAG_API_URL;
+    }
+  });
+
+  function bodiesSent() {
+    return axios.post.mock.calls
+      .filter(([url]) => String(url).endsWith('/query'))
+      .map(([, body]) => body);
+  }
+
+  it('sends entity_id only for agent knowledge-base files', async () => {
+    const tool = await createFileSearchTool({
+      userId: 'user1',
+      entity_id: 'agent_123',
+      files: [
+        { file_id: 'kb-1', filename: 'kb.pdf', fromAgent: true },
+        { file_id: 'user-1', filename: 'attachment.txt', fromAgent: false },
+      ],
+    });
+    await tool.func({ query: 'q' });
+
+    const bodies = bodiesSent();
+    expect(bodies.find((b) => b.file_id === 'kb-1').entity_id).toBe('agent_123');
+    expect(bodies.find((b) => b.file_id === 'user-1').entity_id).toBeUndefined();
+  });
+
+  it('omits entity_id when fromAgent is not set (safe default)', async () => {
+    const tool = await createFileSearchTool({
+      userId: 'user1',
+      entity_id: 'agent_123',
+      files: [{ file_id: 'legacy-1', filename: 'legacy.pdf' }],
+    });
+    await tool.func({ query: 'q' });
+    expect(bodiesSent()[0].entity_id).toBeUndefined();
+  });
+
+  it('sends no entity_id when none is provided', async () => {
+    const tool = await createFileSearchTool({
+      userId: 'user1',
+      files: [{ file_id: 'f1', filename: 'a.txt', fromAgent: true }],
+    });
+    await tool.func({ query: 'q' });
+    expect(bodiesSent()[0].entity_id).toBeUndefined();
+  });
+});