read file and run code
$ sandbox.dispatch(flow_tool_files_read(...)); sandbox.dispatch(flow_tool_code_run(...))

read result

{
  "data": "hello from OpenRath local backend\n"
}

code result

{
  "text": null,
  "stdout": "HELLO FROM OPENRATH LOCAL BACKEND\n\n",
  "stderr": "",
  "error": null
}