📦 refactor: Request Message Sanitization for Smaller Final Response (#10792)

* refactor: implement sanitizeFileForTransmit and sanitizeMessageForTransmit functions for smaller payload to client transmission

* refactor: enhance sanitizeMessageForTransmit to preserve empty files array and avoid mutating original message

* refactor: update sanitizeMessageForTransmit to ensure immutability of files array and improve test clarity

packages/api/src/utils/index.ts

@@ -21,3 +21,4 @@ export { default as Tokenizer, countTokens } from './tokenizer';
 export * from './yaml';
 export * from './http';
 export * from './tokens';
+export * from './message';

packages/api/src/utils/message.spec.ts

@@ -0,0 +1,122 @@
+import { sanitizeFileForTransmit, sanitizeMessageForTransmit } from './message';
+
+describe('sanitizeFileForTransmit', () => {
+  it('should remove text field from file', () => {
+    const file = {
+      file_id: 'test-123',
+      filename: 'test.txt',
+      text: 'This is a very long text content that should be stripped',
+      bytes: 1000,
+    };
+
+    const result = sanitizeFileForTransmit(file);
+
+    expect(result.file_id).toBe('test-123');
+    expect(result.filename).toBe('test.txt');
+    expect(result.bytes).toBe(1000);
+    expect(result).not.toHaveProperty('text');
+  });
+
+  it('should remove _id and __v fields', () => {
+    const file = {
+      file_id: 'test-123',
+      _id: 'mongo-id',
+      __v: 0,
+      filename: 'test.txt',
+    };
+
+    const result = sanitizeFileForTransmit(file);
+
+    expect(result.file_id).toBe('test-123');
+    expect(result).not.toHaveProperty('_id');
+    expect(result).not.toHaveProperty('__v');
+  });
+
+  it('should not modify original file object', () => {
+    const file = {
+      file_id: 'test-123',
+      text: 'original text',
+    };
+
+    sanitizeFileForTransmit(file);
+
+    expect(file.text).toBe('original text');
+  });
+});
+
+describe('sanitizeMessageForTransmit', () => {
+  it('should remove fileContext from message', () => {
+    const message = {
+      messageId: 'msg-123',
+      text: 'Hello world',
+      fileContext: 'This is a very long context that should be stripped',
+    };
+
+    const result = sanitizeMessageForTransmit(message);
+
+    expect(result.messageId).toBe('msg-123');
+    expect(result.text).toBe('Hello world');
+    expect(result).not.toHaveProperty('fileContext');
+  });
+
+  it('should sanitize files array', () => {
+    const message = {
+      messageId: 'msg-123',
+      files: [
+        { file_id: 'file-1', text: 'long text 1', filename: 'a.txt' },
+        { file_id: 'file-2', text: 'long text 2', filename: 'b.txt' },
+      ],
+    };
+
+    const result = sanitizeMessageForTransmit(message);
+
+    expect(result.files).toHaveLength(2);
+    expect(result.files?.[0].file_id).toBe('file-1');
+    expect(result.files?.[0].filename).toBe('a.txt');
+    expect(result.files?.[0]).not.toHaveProperty('text');
+    expect(result.files?.[1]).not.toHaveProperty('text');
+  });
+
+  it('should handle null/undefined message', () => {
+    expect(sanitizeMessageForTransmit(null as unknown as object)).toBeNull();
+    expect(sanitizeMessageForTransmit(undefined as unknown as object)).toBeUndefined();
+  });
+
+  it('should handle message without files', () => {
+    const message = {
+      messageId: 'msg-123',
+      text: 'Hello',
+    };
+
+    const result = sanitizeMessageForTransmit(message);
+
+    expect(result.messageId).toBe('msg-123');
+    expect(result.text).toBe('Hello');
+  });
+
+  it('should create new array reference for empty files array (immutability)', () => {
+    const message = {
+      messageId: 'msg-123',
+      files: [] as { file_id: string }[],
+    };
+
+    const result = sanitizeMessageForTransmit(message);
+
+    expect(result.files).toEqual([]);
+    // New array reference ensures full immutability even for empty arrays
+    expect(result.files).not.toBe(message.files);
+  });
+
+  it('should not modify original message object', () => {
+    const message = {
+      messageId: 'msg-123',
+      fileContext: 'original context',
+      files: [{ file_id: 'file-1', text: 'original text' }],
+    };
+
+    sanitizeMessageForTransmit(message);
+
+    expect(message.fileContext).toBe('original context');
+    expect(message.files[0].text).toBe('original text');
+  });
+});

packages/api/src/utils/message.ts

@@ -0,0 +1,68 @@
+import type { TFile, TMessage } from 'librechat-data-provider';
+
+/** Fields to strip from files before client transmission */
+const FILE_STRIP_FIELDS = ['text', '_id', '__v'] as const;
+
+/** Fields to strip from messages before client transmission */
+const MESSAGE_STRIP_FIELDS = ['fileContext'] as const;
+
+/**
+ * Strips large/unnecessary fields from a file object before transmitting to client.
+ * Use this within existing loops when building file arrays to avoid extra iterations.
+ *
+ * @param file - The file object to sanitize
+ * @returns A new file object without the stripped fields
+ *
+ * @example
+ * // Use in existing file processing loop:
+ * for (const attachment of client.options.attachments) {
+ *   if (messageFiles.has(attachment.file_id)) {
+ *     userMessage.files.push(sanitizeFileForTransmit(attachment));
+ *   }
+ * }
+ */
+export function sanitizeFileForTransmit<T extends Partial<TFile>>(
+  file: T,
+): Omit<T, (typeof FILE_STRIP_FIELDS)[number]> {
+  const sanitized = { ...file };
+  for (const field of FILE_STRIP_FIELDS) {
+    delete sanitized[field as keyof typeof sanitized];
+  }
+  return sanitized;
+}
+
+/**
+ * Sanitizes a message object before transmitting to client.
+ * Removes large fields like `fileContext` and strips `text` from embedded files.
+ *
+ * @param message - The message object to sanitize
+ * @returns A new message object safe for client transmission
+ *
+ * @example
+ * sendEvent(res, {
+ *   final: true,
+ *   requestMessage: sanitizeMessageForTransmit(userMessage),
+ *   responseMessage: response,
+ * });
+ */
+export function sanitizeMessageForTransmit<T extends Partial<TMessage>>(
+  message: T,
+): Omit<T, (typeof MESSAGE_STRIP_FIELDS)[number]> {
+  if (!message) {
+    return message as Omit<T, (typeof MESSAGE_STRIP_FIELDS)[number]>;
+  }
+
+  const sanitized = { ...message };
+
+  // Remove message-level fields
+  for (const field of MESSAGE_STRIP_FIELDS) {
+    delete sanitized[field as keyof typeof sanitized];
+  }
+
+  // Always create a new array when files exist to maintain full immutability
+  if (Array.isArray(sanitized.files)) {
+    sanitized.files = sanitized.files.map((file) => sanitizeFileForTransmit(file));
+  }
+
+  return sanitized;
+}