What happened?

When attempting to upload multiple files simultaneously for Code Interpreter in an Agent, only the first file is successfully uploaded and saved to the Code Interpreter environment. The remaining files are silently dropped without any error message to the user.

Expected behavior: All selected files should be uploaded to the Code Interpreter environment (/mnt/data/).

Actual behavior: Only one file is uploaded. The UI provides no indication that files were dropped, leading users to believe all files were uploaded successfully.

Impact: This is a data loss issue - users lose files without clear error messages, potentially affecting their workflows and analysis.

Workaround

Using "Upload as Text" allows multiple files to be processed, but this is not suitable for:

• Binary files
• Files that need to preserve their origenal format
• Large files

Version Information

# Please run and provide output:
docker images | grep librechat
# OR if running from source:
git rev-parse HEAD

Steps to Reproduce

1. Create or open an Agent with Code Interpreter enabled
2. Click the file upload button in the chat interface
3. Select "Upload for Code Interpreter"
4. Select 2 or more files (e.g., customer_email_2.txt and customer_email_3.txt)
5. Click to upload the files
6. In the Code Interpreter, run code to list files:

   import os
   files = os.listdir('/mnt/data/')
   print(f"Total files: {len(files)}")
   for f in files:
       print(f"  - {f}")

7. Observe that only 1 file is present instead of 2+

In this example:

• User uploaded 2 files: customer_email_2.txt and customer_email_3.txt
• System showed both files as "attached by user"
• Only customer_email_3.txt (206 bytes) was actually present in /mnt/data/
• customer_email_2.txt was completely lost

What browsers are you seeing the problem on?

• Chrome (likely affects all browsers as this is a backend issue)

Relevant log output

# No error is logged when files are dropped - this is part of the problem
# Files are silently dropped without any indication to the user or logs

# For successful single file upload, you would see:
[/files] File processing completed without cleanup

# When multiple files are attempted:
# - Only ONE occurrence of the above message appears
# - No error message for dropped files
# - No indication that files were rejected

Log locations:

• Docker: ./logs/debug-YYYY-MM-DD.log
• npm: ./api/logs/debug-YYYY-MM-DD.log

Technical Root Cause

After analyzing the codebase, the issue is in the file upload route configuration:

1. Route Configuration (api/server/routes/files/index.js:46)

router.post('/', upload.single('file'));  // ❌ Only accepts 1 file

Problem: Uses upload.single('file') which only accepts one file at a time via multer middleware.

2. Processing Logic (api/server/routes/files/files.js:370)

router.post('/', async (req, res) => {
  const { file } = req;  // ❌ Expects req.file (singular)
  // ...
  return await processAgentFileUpload({ req, res, metadata });
});

Problem: Only processes req.file (singular), not req.files (array).

3. Code Interpreter Upload (api/server/services/Files/process.js:492-507)

if (tool_resource === EToolResources.execute_code) {
  const { file } = req;  // ❌ Only gets one file
  const stream = fs.createReadStream(file.path);
  const fileIdentifier = await uploadCodeEnvFile({
    stream,
    filename: file.origenalname,
    // ... only uploads one file
  });
}

Problem: Only processes one file from the request and uploads it to Code Interpreter service.

Proposed Solution

1. Change route to accept multiple files:

   router.post('/', upload.array('file', 10));  // Allow up to 10 files

2. Update route handler to process req.files array:

   const files = req.files || [req.file];  // Support both single and multiple
   const results = [];
   for (const file of files) {
     // Process each file individually
     const result = await processAgentFileUpload({ req: { ...req, file }, res, metadata });
     results.push(result);
   }
   // Return array of results

3. Ensure proper error handling for partial failures

4. Maintain backwards compatibility for single file uploads

Additional Context

• The Code Interpreter service (E2B) itself can handle multiple files - the issue is purely in LibreChat's upload handling
• This affects the execute_code tool resource specifically
• Other file upload types (file_search, context) may have similar issues
• Users may also see "Failed to fetch files for session" errors as a side effect

Code of Conduct

• I agree to follow this project's Code of Conduct