agents.md file is somehow only visible through filesystem tools but not through python

There is something a bit strange going on with the CompositeBackend.

For example, if you ask for the contents of the Agents.md file, and if the LLM decides to use read_file then it can actually find the file. However, if you ask it to do so through a python script, so that it writes something like this:

import os

  os.makedirs('/sandbox', exist_ok=True)
  path = '/sandbox/memory/AGENTS.md'
  print('path:', path)
  print('exists:', os.path.exists(path))
  print('readable:', os.access(path, os.R_OK))
  try:
      with open(path, 'r', encoding='utf-8') as f:
          print(f.read())
  except Exception as e:
      print('error:', type(e).__name__, str(e))

It fails for some reason.. it seems the CompositeBackend doesn't work through Python!

The LLM eventually replies with..

I wrote and ran a Python script to read /sandbox/memory/AGENTS.md.
Result:

exists: False

readable: False

FileNotFoundError


So the same pattern holds:

filesystem tools can see /sandbox/memory/AGENTS.md

Python execution cannot access it


This suggests the execution environment and filesystem tools are seeing different mounted views of /sandbox.

Start by tracing the CompositeBackend behavior for filesystem tools and Python execution, using the reported /sandbox/memory/AGENTS.md example as the reproduction. Compare the filesystem views available to each path and define done as making the file consistently visible, or documenting the intended boundary with a regression test.