diff --git a/client/src/components/SidePanel/Files/PanelTable.tsx b/client/src/components/SidePanel/Files/PanelTable.tsx
index 2fc8f7031b..e67e16abdd 100644
--- a/client/src/components/SidePanel/Files/PanelTable.tsx
+++ b/client/src/components/SidePanel/Files/PanelTable.tsx
@@ -24,14 +24,14 @@ import {
   type ColumnFiltersState,
 } from '@tanstack/react-table';
 import {
-  fileConfig as defaultFileConfig,
-  checkOpenAIStorage,
-  mergeFileConfig,
   megabyte,
+  mergeFileConfig,
+  checkOpenAIStorage,
   isAssistantsEndpoint,
   getEndpointFileConfig,
-  type TFile,
+  fileConfig as defaultFileConfig,
 } from 'librechat-data-provider';
+import type { TFile } from 'librechat-data-provider';
 import { MyFilesModal } from '~/components/Chat/Input/Files/MyFilesModal';
 import { useFileMapContext, useChatContext } from '~/Providers';
 import { useLocalize, useUpdateFiles } from '~/hooks';
@@ -86,7 +86,7 @@ export default function DataTable<TData, TValue>({ columns, data }: DataTablePro
 
   const fileMap = useFileMapContext();
   const { showToast } = useToastContext();
-  const { setFiles, conversation } = useChatContext();
+  const { files, setFiles, conversation } = useChatContext();
   const { data: fileConfig = null } = useGetFileConfig({
     select: (data) => mergeFileConfig(data),
   });
@@ -142,7 +142,15 @@ export default function DataTable<TData, TValue>({ columns, data }: DataTablePro
         return;
       }
 
-      if (fileData.bytes > (endpointFileConfig.fileSizeLimit ?? Number.MAX_SAFE_INTEGER)) {
+      if (endpointFileConfig.fileLimit && files.size >= endpointFileConfig.fileLimit) {
+        showToast({
+          message: `${localize('com_ui_attach_error_limit')} ${endpointFileConfig.fileLimit} files (${endpoint})`,
+          status: 'error',
+        });
+        return;
+      }
+
+      if (fileData.bytes >= (endpointFileConfig.fileSizeLimit ?? Number.MAX_SAFE_INTEGER)) {
         showToast({
           message: `${localize('com_ui_attach_error_size')} ${
             (endpointFileConfig.fileSizeLimit ?? 0) / megabyte
@@ -160,6 +168,22 @@ export default function DataTable<TData, TValue>({ columns, data }: DataTablePro
         return;
       }
 
+      if (endpointFileConfig.totalSizeLimit) {
+        const existing = files.get(fileData.file_id);
+        let currentTotalSize = 0;
+        for (const f of files.values()) {
+          currentTotalSize += f.size;
+        }
+        currentTotalSize -= existing?.size ?? 0;
+        if (currentTotalSize + fileData.bytes > endpointFileConfig.totalSizeLimit) {
+          showToast({
+            message: `${localize('com_ui_attach_error_total_size')} ${endpointFileConfig.totalSizeLimit / megabyte} MB (${endpoint})`,
+            status: 'error',
+          });
+          return;
+        }
+      }
+
       addFile({
         progress: 1,
         attached: true,
@@ -175,7 +199,7 @@ export default function DataTable<TData, TValue>({ columns, data }: DataTablePro
         metadata: fileData.metadata,
       });
     },
-    [addFile, fileMap, conversation, localize, showToast, fileConfig],
+    [addFile, files, fileMap, conversation, localize, showToast, fileConfig],
   );
 
   const filenameFilter = table.getColumn('filename')?.getFilterValue() as string;
diff --git a/client/src/components/SidePanel/Files/__tests__/PanelTable.spec.tsx b/client/src/components/SidePanel/Files/__tests__/PanelTable.spec.tsx
new file mode 100644
index 0000000000..2639d3c100
--- /dev/null
+++ b/client/src/components/SidePanel/Files/__tests__/PanelTable.spec.tsx
@@ -0,0 +1,239 @@
+import React from 'react';
+import { render, screen, fireEvent } from '@testing-library/react';
+import { FileSources } from 'librechat-data-provider';
+import type { TFile } from 'librechat-data-provider';
+import type { ExtendedFile } from '~/common';
+import DataTable from '../PanelTable';
+import { columns } from '../PanelColumns';
+
+const mockShowToast = jest.fn();
+const mockAddFile = jest.fn();
+
+let mockFileMap: Record<string, TFile> = {};
+let mockFiles: Map<string, ExtendedFile> = new Map();
+let mockConversation: Record<string, unknown> | null = { endpoint: 'openAI' };
+let mockRawFileConfig: Record<string, unknown> | null = {
+  endpoints: {
+    openAI: { fileLimit: 10, supportedMimeTypes: ['application/pdf', 'text/plain'] },
+  },
+};
+
+jest.mock('@librechat/client', () => ({
+  Table: ({ children, ...props }: { children: React.ReactNode }) => (
+    <table {...props}>{children}</table>
+  ),
+  Button: ({
+    children,
+    ...props
+  }: { children: React.ReactNode } & React.ButtonHTMLAttributes<HTMLButtonElement>) => (
+    <button {...props}>{children}</button>
+  ),
+  TableRow: ({ children, ...props }: { children: React.ReactNode }) => (
+    <tr {...props}>{children}</tr>
+  ),
+  TableHead: ({ children, ...props }: { children: React.ReactNode }) => (
+    <th {...props}>{children}</th>
+  ),
+  TableBody: ({ children, ...props }: { children: React.ReactNode }) => (
+    <tbody {...props}>{children}</tbody>
+  ),
+  TableCell: ({
+    children,
+    ...props
+  }: { children: React.ReactNode } & React.TdHTMLAttributes<HTMLTableCellElement>) => (
+    <td {...props}>{children}</td>
+  ),
+  FilterInput: () => <input data-testid="filter" />,
+  TableHeader: ({ children, ...props }: { children: React.ReactNode }) => (
+    <thead {...props}>{children}</thead>
+  ),
+  useToastContext: () => ({ showToast: mockShowToast }),
+}));
+
+jest.mock('~/Providers', () => ({
+  useFileMapContext: () => mockFileMap,
+  useChatContext: () => ({
+    files: mockFiles,
+    setFiles: jest.fn(),
+    conversation: mockConversation,
+  }),
+}));
+
+jest.mock('~/hooks', () => ({
+  useLocalize: () => (key: string) => key,
+  useUpdateFiles: () => ({ addFile: mockAddFile }),
+}));
+
+jest.mock('~/data-provider', () => ({
+  useGetFileConfig: ({ select }: { select?: (d: unknown) => unknown }) => ({
+    data: select != null ? select(mockRawFileConfig) : mockRawFileConfig,
+  }),
+}));
+
+jest.mock('~/components/Chat/Input/Files/MyFilesModal', () => ({
+  MyFilesModal: () => null,
+}));
+
+jest.mock('../PanelFileCell', () => ({ row }: { row: { original: TFile } }) => (
+  <span>{row.original?.filename}</span>
+));
+
+function makeFile(overrides: Partial<TFile> = {}): TFile {
+  return {
+    user: 'user-1',
+    file_id: 'file-1',
+    bytes: 1024,
+    embedded: false,
+    filename: 'test.pdf',
+    filepath: '/files/test.pdf',
+    object: 'file',
+    type: 'application/pdf',
+    usage: 0,
+    source: FileSources.local,
+    ...overrides,
+  };
+}
+
+function makeExtendedFile(overrides: Partial<ExtendedFile> = {}): ExtendedFile {
+  return {
+    file_id: 'ext-1',
+    size: 1024,
+    progress: 1,
+    source: FileSources.local,
+    ...overrides,
+  };
+}
+
+function renderTable(data: TFile[]) {
+  return render(<DataTable columns={columns} data={data} />);
+}
+
+function clickFilenameCell() {
+  const cells = screen.getAllByRole('button');
+  const filenameCell = cells.find(
+    (cell) => cell.tagName === 'TD' && cell.textContent && !cell.textContent.includes('com_ui_'),
+  );
+  if (!filenameCell) {
+    throw new Error('Could not find filename cell with role="button" — check mock setup');
+  }
+  fireEvent.click(filenameCell);
+  return filenameCell;
+}
+
+describe('PanelTable handleFileClick', () => {
+  beforeEach(() => {
+    mockShowToast.mockClear();
+    mockAddFile.mockClear();
+    mockFiles = new Map();
+    mockConversation = { endpoint: 'openAI' };
+    mockRawFileConfig = {
+      endpoints: {
+        openAI: {
+          fileLimit: 5,
+          totalSizeLimit: 10,
+          supportedMimeTypes: ['application/pdf', 'text/plain'],
+        },
+      },
+    };
+  });
+
+  it('calls addFile when within file limits', () => {
+    const file = makeFile();
+    mockFileMap = { [file.file_id]: file };
+
+    renderTable([file]);
+    clickFilenameCell();
+
+    expect(mockAddFile).toHaveBeenCalledTimes(1);
+    expect(mockAddFile).toHaveBeenCalledWith(
+      expect.objectContaining({
+        file_id: file.file_id,
+        attached: true,
+        progress: 1,
+      }),
+    );
+    expect(mockShowToast).not.toHaveBeenCalledWith(expect.objectContaining({ status: 'error' }));
+  });
+
+  it('blocks attachment when fileLimit is reached', () => {
+    const file = makeFile({ file_id: 'new-file', filename: 'new.pdf' });
+    mockFileMap = { [file.file_id]: file };
+
+    mockFiles = new Map(
+      Array.from({ length: 5 }, (_, i) => [
+        `existing-${i}`,
+        makeExtendedFile({ file_id: `existing-${i}` }),
+      ]),
+    );
+
+    renderTable([file]);
+    clickFilenameCell();
+
+    expect(mockAddFile).not.toHaveBeenCalled();
+    expect(mockShowToast).toHaveBeenCalledWith(
+      expect.objectContaining({
+        message: expect.stringContaining('com_ui_attach_error_limit'),
+        status: 'error',
+      }),
+    );
+  });
+
+  it('blocks attachment when totalSizeLimit would be exceeded', () => {
+    const MB = 1024 * 1024;
+    const largeFile = makeFile({ file_id: 'large-file', bytes: 6 * MB });
+    mockFileMap = { [largeFile.file_id]: largeFile };
+
+    mockFiles = new Map([
+      ['existing-1', makeExtendedFile({ file_id: 'existing-1', size: 5 * MB })],
+    ]);
+
+    renderTable([largeFile]);
+    clickFilenameCell();
+
+    expect(mockAddFile).not.toHaveBeenCalled();
+    expect(mockShowToast).toHaveBeenCalledWith(
+      expect.objectContaining({
+        message: expect.stringContaining('com_ui_attach_error_total_size'),
+        status: 'error',
+      }),
+    );
+  });
+
+  it('does not double-count size of already-attached file', () => {
+    const MB = 1024 * 1024;
+    const file = makeFile({ file_id: 'reattach', bytes: 5 * MB });
+    mockFileMap = { [file.file_id]: file };
+
+    mockFiles = new Map([
+      ['reattach', makeExtendedFile({ file_id: 'reattach', size: 5 * MB })],
+      ['other', makeExtendedFile({ file_id: 'other', size: 4 * MB })],
+    ]);
+
+    renderTable([file]);
+    clickFilenameCell();
+
+    expect(mockAddFile).toHaveBeenCalledTimes(1);
+    expect(mockShowToast).not.toHaveBeenCalledWith(
+      expect.objectContaining({
+        message: expect.stringContaining('com_ui_attach_error_total_size'),
+      }),
+    );
+  });
+
+  it('allows attachment when just under fileLimit', () => {
+    const file = makeFile({ file_id: 'under-limit' });
+    mockFileMap = { [file.file_id]: file };
+
+    mockFiles = new Map(
+      Array.from({ length: 4 }, (_, i) => [
+        `existing-${i}`,
+        makeExtendedFile({ file_id: `existing-${i}` }),
+      ]),
+    );
+
+    renderTable([file]);
+    clickFilenameCell();
+
+    expect(mockAddFile).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/client/src/locales/en/translation.json b/client/src/locales/en/translation.json
index 196ea2ad4a..f45cdd5f8c 100644
--- a/client/src/locales/en/translation.json
+++ b/client/src/locales/en/translation.json
@@ -748,7 +748,9 @@
   "com_ui_attach_error": "Cannot attach file. Create or select a conversation, or try refreshing the page.",
   "com_ui_attach_error_disabled": "File uploads are disabled for this endpoint",
   "com_ui_attach_error_openai": "Cannot attach Assistant files to other endpoints",
+  "com_ui_attach_error_limit": "File limit reached:",
   "com_ui_attach_error_size": "File size limit exceeded for endpoint:",
+  "com_ui_attach_error_total_size": "Total file size limit exceeded for endpoint:",
   "com_ui_attach_error_type": "Unsupported file type for endpoint:",
   "com_ui_attach_remove": "Remove file",
   "com_ui_attach_warn_endpoint": "Non-Assistant files may be ignored without a compatible tool",
diff --git a/client/src/utils/__tests__/validateFiles.spec.ts b/client/src/utils/__tests__/validateFiles.spec.ts
new file mode 100644
index 0000000000..6d690bf62a
--- /dev/null
+++ b/client/src/utils/__tests__/validateFiles.spec.ts
@@ -0,0 +1,172 @@
+import { megabyte, fileConfig as defaultFileConfig } from 'librechat-data-provider';
+import type { EndpointFileConfig, FileConfig } from 'librechat-data-provider';
+import type { ExtendedFile } from '~/common';
+import { validateFiles } from '../files';
+
+const supportedMimeTypes = defaultFileConfig.endpoints.default.supportedMimeTypes;
+
+function makeEndpointConfig(overrides: Partial<EndpointFileConfig> = {}): EndpointFileConfig {
+  return {
+    fileLimit: 10,
+    fileSizeLimit: 25 * megabyte,
+    totalSizeLimit: 100 * megabyte,
+    supportedMimeTypes,
+    disabled: false,
+    ...overrides,
+  };
+}
+
+function makeFile(name: string, type: string, size: number): File {
+  const content = new ArrayBuffer(size);
+  return new File([content], name, { type });
+}
+
+function makeExtendedFile(overrides: Partial<ExtendedFile> = {}): ExtendedFile {
+  return {
+    file_id: 'ext-1',
+    size: 1024,
+    progress: 1,
+    type: 'application/pdf',
+    ...overrides,
+  };
+}
+
+describe('validateFiles', () => {
+  let setError: jest.Mock;
+  let files: Map<string, ExtendedFile>;
+  let endpointFileConfig: EndpointFileConfig;
+  const fileConfig: FileConfig | null = null;
+
+  beforeEach(() => {
+    setError = jest.fn();
+    files = new Map();
+    endpointFileConfig = makeEndpointConfig();
+  });
+
+  it('returns true when all checks pass', () => {
+    const fileList = [makeFile('doc.pdf', 'application/pdf', 1024)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(true);
+    expect(setError).not.toHaveBeenCalled();
+  });
+
+  it('rejects when endpoint is disabled', () => {
+    endpointFileConfig = makeEndpointConfig({ disabled: true });
+    const fileList = [makeFile('doc.pdf', 'application/pdf', 1024)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(false);
+    expect(setError).toHaveBeenCalledWith('com_ui_attach_error_disabled');
+  });
+
+  it('rejects empty files (zero bytes)', () => {
+    const fileList = [makeFile('empty.pdf', 'application/pdf', 0)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(false);
+    expect(setError).toHaveBeenCalledWith('com_error_files_empty');
+  });
+
+  it('rejects when fileLimit would be exceeded', () => {
+    endpointFileConfig = makeEndpointConfig({ fileLimit: 3 });
+    files = new Map([
+      ['f1', makeExtendedFile({ file_id: 'f1', filename: 'one.pdf', size: 2048 })],
+      ['f2', makeExtendedFile({ file_id: 'f2', filename: 'two.pdf', size: 3072 })],
+    ]);
+    const fileList = [
+      makeFile('a.pdf', 'application/pdf', 1024),
+      makeFile('b.pdf', 'application/pdf', 2048),
+    ];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(false);
+    expect(setError).toHaveBeenCalledWith('File limit reached: 3 files');
+  });
+
+  it('allows upload when exactly at fileLimit boundary', () => {
+    endpointFileConfig = makeEndpointConfig({ fileLimit: 3 });
+    files = new Map([
+      ['f1', makeExtendedFile({ file_id: 'f1', filename: 'one.pdf', size: 2048 })],
+      ['f2', makeExtendedFile({ file_id: 'f2', filename: 'two.pdf', size: 3072 })],
+    ]);
+    const fileList = [makeFile('a.pdf', 'application/pdf', 1024)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(true);
+  });
+
+  it('rejects unsupported MIME type', () => {
+    const fileList = [makeFile('data.xyz', 'application/x-unknown', 1024)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(false);
+    expect(setError).toHaveBeenCalledWith('Unsupported file type: application/x-unknown');
+  });
+
+  it('rejects when file size equals fileSizeLimit (>= comparison)', () => {
+    const limit = 5 * megabyte;
+    endpointFileConfig = makeEndpointConfig({ fileSizeLimit: limit });
+    const fileList = [makeFile('exact.pdf', 'application/pdf', limit)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(false);
+    expect(setError).toHaveBeenCalledWith(`File size limit exceeded: ${limit / megabyte} MB`);
+  });
+
+  it('allows file just under fileSizeLimit', () => {
+    const limit = 5 * megabyte;
+    endpointFileConfig = makeEndpointConfig({ fileSizeLimit: limit });
+    const fileList = [makeFile('under.pdf', 'application/pdf', limit - 1)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(true);
+  });
+
+  it('rejects when totalSizeLimit would be exceeded', () => {
+    const limit = 10 * megabyte;
+    endpointFileConfig = makeEndpointConfig({ totalSizeLimit: limit });
+    files = new Map([['f1', makeExtendedFile({ file_id: 'f1', size: 6 * megabyte })]]);
+    const fileList = [makeFile('big.pdf', 'application/pdf', 5 * megabyte)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(false);
+    expect(setError).toHaveBeenCalledWith(`Total file size limit exceeded: ${limit / megabyte} MB`);
+  });
+
+  it('allows when totalSizeLimit is exactly met', () => {
+    const limit = 10 * megabyte;
+    endpointFileConfig = makeEndpointConfig({ totalSizeLimit: limit });
+    files = new Map([['f1', makeExtendedFile({ file_id: 'f1', size: 5 * megabyte })]]);
+    const fileList = [makeFile('fits.pdf', 'application/pdf', 5 * megabyte)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(true);
+  });
+
+  it('rejects duplicate files', () => {
+    files = new Map([
+      [
+        'f1',
+        makeExtendedFile({
+          file_id: 'f1',
+          file: makeFile('doc.pdf', 'application/pdf', 1024),
+          filename: 'doc.pdf',
+          size: 1024,
+          type: 'application/pdf',
+        }),
+      ],
+    ]);
+    const fileList = [makeFile('doc.pdf', 'application/pdf', 1024)];
+    const result = validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(result).toBe(false);
+    expect(setError).toHaveBeenCalledWith('com_error_files_dupe');
+  });
+
+  it('enforces check ordering: disabled before fileLimit', () => {
+    endpointFileConfig = makeEndpointConfig({ disabled: true, fileLimit: 1 });
+    files = new Map([['f1', makeExtendedFile({ file_id: 'f1', filename: 'existing.pdf' })]]);
+    const fileList = [makeFile('doc.pdf', 'application/pdf', 1024)];
+    validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(setError).toHaveBeenCalledWith('com_ui_attach_error_disabled');
+  });
+
+  it('enforces check ordering: fileLimit before fileSizeLimit', () => {
+    const limit = 1;
+    endpointFileConfig = makeEndpointConfig({ fileLimit: 1, fileSizeLimit: limit });
+    files = new Map([['f1', makeExtendedFile({ file_id: 'f1', filename: 'existing.pdf' })]]);
+    const fileList = [makeFile('huge.pdf', 'application/pdf', limit)];
+    validateFiles({ files, fileList, setError, endpointFileConfig, fileConfig });
+    expect(setError).toHaveBeenCalledWith('File limit reached: 1 files');
+  });
+});
diff --git a/client/src/utils/files.ts b/client/src/utils/files.ts
index b4d362d456..be81a31b79 100644
--- a/client/src/utils/files.ts
+++ b/client/src/utils/files.ts
@@ -251,7 +251,7 @@ export const validateFiles = ({
   const currentTotalSize = existingFiles.reduce((total, file) => total + file.size, 0);
 
   if (fileLimit && fileList.length + files.size > fileLimit) {
-    setError(`You can only upload up to ${fileLimit} files at a time.`);
+    setError(`File limit reached: ${fileLimit} files`);
     return false;
   }
 
@@ -282,19 +282,18 @@ export const validateFiles = ({
     }
 
     if (!checkType(originalFile.type, mimeTypesToCheck)) {
-      console.log(originalFile);
-      setError('Currently, unsupported file type: ' + originalFile.type);
+      setError(`Unsupported file type: ${originalFile.type}`);
       return false;
     }
 
     if (fileSizeLimit && originalFile.size >= fileSizeLimit) {
-      setError(`File size exceeds ${fileSizeLimit / megabyte} MB.`);
+      setError(`File size limit exceeded: ${fileSizeLimit / megabyte} MB`);
       return false;
     }
   }
 
   if (totalSizeLimit && currentTotalSize + incomingTotalSize > totalSizeLimit) {
-    setError(`The total size of the files cannot exceed ${totalSizeLimit / megabyte} MB.`);
+    setError(`Total file size limit exceeded: ${totalSizeLimit / megabyte} MB`);
     return false;
   }