How a script or plain shell runs a command on a client Mac without an agent (byre client-exec), and how to check either Mac's screen lock (byre screen).
# Running commands on a client Mac from a shell
`client_bash` needs an agent. For a script or plain shell on the machine byre runs on, such as a wrapper that fetches a token from the human's Mac, use:
`byre` is `/Applications/Byre.app/Contents/Helpers/byre` on every Mac with the app.
- It runs CMD as `client_bash` does: zsh as a login shell in the home directory, in the app's session, as the human. That session is what GUI-only commands need.
- Without `--client` it picks the most recently active client, the one `list_clients` lists first.
- Each argument reaches the client as one word, so shell syntax needs `-- zsh -c '...'`.
- The command's stdout and stderr come back separately and byte for byte, once it ends, written to client-exec's own stdout and stderr.
- Exit status: the command's own; 75 when no client is connected, it didn't acknowledge the request within 2s, or it disconnected; 124 when `--timeout` (default 30s) killed it. A one-line `byre client-exec: ...` on stderr says why.
## Credentials
It needs `BYRE_TOKEN`, which byre sets for everything it starts: agents, their tools and the processes those run, and the task's terminals. A process byre didn't start reads it from `loopback-token` in byre's data directory (`~/Library/Application Support/byre/` by default); it changes every time byre restarts, so read it at each call:
client-exec calls byre's API at `http://127.0.0.1:8270`. When `HTTP_PROXY` (or `http_proxy`) is set it sends that call through the proxy, loopback included, unless `NO_PROXY` lists the address; a sandbox that denies direct loopback connections then needs only to allow `127.0.0.1:8270` through its proxy. `BYRE_NO_PROXY=1` connects directly whatever the proxy variables say.
`byre screen` prints `unlocked`, `locked` or `no-session` (no GUI login for this user) for the Mac it runs on, and exits 0. Check the server Mac with `byre screen` and the client with:
