Hey everyone! I’ve been building an MCP server that processes user-uploaded images, and I’ve run into a significant issue with the ChatGPT mobile app (both iOS and Android).
THE PROBLEM
When users upload images from the mobile app and my MCP tool tries to process them, the server receives incomplete file references instead of downloadable URLs:
Expected (works on web):
{
"file_id": "file-abc123",
"download_url": "https://files.oaiusercontent.com/...",
"name": "photo.jpg",
"mime_type": "image/jpeg"
}
Actual (mobile app):
"chat_upload"
Just a string! No download URL, no metadata, nothing the server can use to fetch the file.
IMPACT
This means:
File upload features work on web but completely fail on mobile
Users get a broken experience depending on which platform they use
No way to build cross-platform MCP tools that handle user files
WHAT I’VE TRIED
• Parsing the string reference (doesn’t provide enough info)
• Asking users for base64 (breaks UX and doesn’t work for app-managed uploads)
• Looking for server-side APIs to resolve the reference (none exist AFAIK)
THE ASK
Has anyone else encountered this? Any workarounds I’m missing?
I’ve opened a detailed issue on GitHub with full reproduction steps and proposed solutions:
GitHub Issue #185: Mobile file uploads in ChatGPT app send incomplete file references instead of downloadable URLs · Issue #185 · openai/openai-apps-sdk-examples · GitHub
Tags: mcp mobile file-upload bug