API 500 Internal Server Error when reading PDF files

Problem

Claude Code throws API 500 errors when reading PDF files. Tested multiple PDFs (~132KB, ~494KB), same error every time.

API Error: 500 {"type":"error","error":{"type":"api_error","message":"Internal server error"},"request_id":"req_011CXN4shvYfyXQ2AeV8HsBv"}

Environment

• Claude Code v2.1.15, Opus 4.5, Windows 11 (MSYS2/Git Bash)
• Date: 2026-01-22 ~08:50 UTC
• status.anthropic.com showed "All Systems Operational"

What I found

This also breaks claude.ai Projects that have PDFs in their Project Files section. The whole project stops working - even text-only messages fail silently (spinner appears, then returns to pre-send state with no error).

Removing PDFs from Project Files fixes it immediately.

What still works

• Uploading PDFs directly in a chat message (standalone or in a project)
• Everything except Project Files with PDFs

Workaround

Remove PDFs from Project Files. You can still upload them per-message.