LLeMbas/deploy

Deployment

Installs LLeMbas as a system service behind nginx with a self-signed certificate. Written for a systemd + nginx host; tested on Arch.

	Default
Service user	lembas (system account, nologin)
Home	/home/lembas
Install prefix	/srv/lembas (bind mount of the home)
Checkout	$PREFIX/app
Virtualenv	$PREFIX/venv
Database	$PREFIX/data/lembas.db
Environment	$PREFIX/lembas.env (mode 600)
Unit	/etc/systemd/system/lembas.service
Vhost	/etc/nginx/conf.d/<host>.conf
Listens on	127.0.0.1:8080 — reachable only through nginx

The prefix defaults to a bind mount of the service user's home because on many machines the root filesystem is small while /home is not, and the virtualenv plus database belong on the larger volume. Set PREFIX=$HOME_DIR to skip it.

First install

SITE_HOST=chat.example ./deploy/install.sh

Idempotent — safe to re-run. It creates the user and bind mount, clones the repo, builds the venv, generates lembas.env with a fresh LEMBAS_SECRET_KEY, installs the unit and vhost, issues a self-signed certificate, adds a /etc/hosts entry if the name does not already resolve, and enables the service.

Then open https://<SITE_HOST>, accept the certificate warning, and create the first account — it becomes the administrator.

Everything is overridable from the environment:

Variable	Default
SITE_HOST	lembas.local	nginx server_name and certificate CN
APP_PORT	8080	loopback port the service binds
SERVICE_USER	lembas	system account to run as
HOME_DIR	/home/lembas	that account's home
PREFIX	/srv/lembas	install root (bind mount of HOME_DIR)
REPO_URL	this checkout's origin	so a fork deploys itself
LEMBAS_BRANCH	main	branch to deploy

Deploying a change

git push
./deploy/update.sh

update.sh fetches, hard-resets the deployment checkout to origin/main, reinstalls dependencies and restarts, printing the commits it pulled. The hard reset is deliberate: nothing is ever edited in place there, so there is no local work to preserve and no conflicts to resolve.

Operating it

systemctl status lembas
journalctl -u lembas -f
sudo -u lembas /srv/lembas/venv/bin/lembas info      # paths and counts

Configuration lives in $PREFIX/lembas.env. Edit it and restart.

Notes

The secret key is generated once. install.sh will not overwrite an existing lembas.env. Rotating LEMBAS_SECRET_KEY signs every user out and makes stored upstream API keys unreadable — they would have to be re-entered.

nginx buffering is off for a reason. Replies stream as server-sent events. With proxy_buffering on (the default) nginx holds the entire reply and delivers it in one lump at the end, which is indistinguishable from streaming being broken. proxy_read_timeout is raised to an hour because a model can think for minutes before the first token.

The vhost passes WebSocket upgrades through, and must. The terminal panel is the one WebSocket in LLeMbas. A location that sets Connection "" — which is what SSE alone needs, and what this template used to say — fails every handshake, and a failed handshake tells the browser nothing: no status, no reason. The map $http_upgrade at the top of the vhost yields the empty string when the client did not ask to upgrade, so streaming is unaffected. update.sh warns when the installed vhost has drifted from the template, because this is the failure most likely to be diagnosed as a bug in the application.

Every restart kills every open shell. A reply being written is persisted with whatever it has; a terminal has nothing to persist, so a command still running on the far side is cut off. update.sh restarts unconditionally, so a deploy in the middle of somebody's apt-get dist-upgrade ends it. The panel is told why rather than silently reconnecting to a new shell, which would have lost the working directory and the half-typed command.

A terminal is not in the transcript, and is not logged. The open and the close are logged with the user, the chat and the connection; what was typed is not recorded anywhere. That follows from the design — the chat's mode governs the model, not the person at the keyboard — but everything else an agent chat does is in the transcript, so it is a difference in kind and worth knowing before somebody goes looking for the history.

Nothing an agent does runs on this machine. Agent chats execute their commands over SSH, on a host somebody added and prepared — a container, a VM, another machine. That is the whole isolation story, and it is why the unit can stay locked down instead of being opened up to make room for a sandbox.

ProtectSystem=full rather than strict only because the data directory must be writable and strict would mean listing every path.

The practical consequence for whoever runs this: the security of an agent chat is the security of the host behind its SSH profile. A throwaway container with the one project mounted into it is a very different thing from a key to a production server, and LLeMbas cannot tell them apart.

Use a real certificate if this is exposed beyond a trusted LAN. The self-signed cert exists so the install works with no external dependencies; point ssl_certificate at a real one and nothing else needs to change.

The session cookie is deliberately not marked secure, so that a LAN install over plain http can sign anybody in at all. That has always meant a network attacker on http could steal a session; with the terminal it also means they could open an interactive shell on the machine behind that chat. If the terminal is switched on, run this over TLS.

One worker only. True of generations already — the registry is in-process — and sharper here: with two workers a browser reconnecting to its terminal could land in the process that has no shell for it, and silently open a second one on the same machine.