#Several keys for one service

The thing you hit every day: a personal key for a service, another for work, another for a client. Same variable name, different values. Each is a set:

hush add fal --as "Personal fal" --library    # hush knows fal needs FAL_KEY; asks, hidden
hush add fal --as "Work fal" --library
hush add fal --as "Client fal" --library

Use one per project, or one per run:

hush use work-fal                             # this project, from now on
hush run --use client-fal -- ./build.sh       # this run only — layered last, so it wins

Unknown service? Tell it the variables once:

hush add myapi --as "Staging myapi" --vars MYAPI_KEY,MYAPI_SECRET

From a script or CI, pipe one line per variable, in the order hush asks:

printf '%s\n' "$FAL_KEY" | hush add fal --as "CI fal"
printf '%s\n%s\n' "$SID" "$TOKEN" | hush add twilio --as "Main twilio"

If nothing arrives on stdin, hush add fails rather than reporting success — a run that stored no credential must not look like one that did.