# the untrusted server's endpoint reaches the operating system
$ sabline attack.vel --allow io,fs:read:.,ffi:json --receipt receipt.json
opening the endpoint the server named
error[E311] 'py' reaches into Python module 'os', which this run does not allow
  --> attack.vel, line 10
  how to fix (pick one):
    1. allow it: --allow ffi:os,json
    2. or use a program that does not need it
  reference: https://sabline.dev/llms.txt
exit 1

# and with no ffi grant at all
$ sabline attack.vel --allow io,fs:read:.
opening the endpoint the server named
error[E310] 'py' needs the 'ffi' effect, which this run does not allow (it allows: fs:read:.,io)
  --> attack.vel, line 10
  how to fix (pick one):
    1. allow it: sabline <file> --allow fs:read:.,io,ffi
    2. a run with no --allow gets io (5.0); --allow all grants every effect
    3. or use a program that does not need it
  reference: https://sabline.dev/llms.txt
exit 1
