Add registration toggle and password change; genericise deploy

Two things the running instance needed.

**Registration toggle.** Admin -> General, backed by a new settings table
group rather than the environment. LEMBAS_ALLOW_SIGNUP now seeds only the
initial value: once an administrator saves the setting, the stored value
wins. The alternative -- environment always winning -- means a toggle in
the UI silently reverts on the next restart, which is worse than not
offering one. Closing registration also removes the "Create one" link
from the sign-in page, so the link never leads somewhere that refuses.

**Password change**, on the user settings page. Changing a password
revokes every other session and immediately re-issues a cookie for the
current one: if the reason for the change is that somebody else knows
the password, leaving their session alive defeats the point, but signing
the user out of the tab they are standing in is merely rude.

**deploy/ is now host-agnostic.** This repository is public, so the unit
and vhost became templates with __PREFIX__ / __SITE_HOST__ / __APP_PORT__
substituted at install time, and every path, hostname and port moved to
environment variables. REPO_URL defaults to the checkout's own origin so
a fork deploys itself. Machine-specific values belong in private notes,
not here -- CLAUDE.md now says so.

83 tests, ruff clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.env.example

@@ -20,8 +20,10 @@ LEMBAS_RELOAD=false
 # debug | info | warning | error
 LEMBAS_LOG_LEVEL=info
 
-# Allow new accounts to register themselves. The very first account created is
+# Allow new accounts to register themselves. This is only the INITIAL value:
-# always an admin, regardless of this setting. Turn off once your users exist.
+# once an administrator sets it under Admin -> General, the stored setting wins
+# and this variable is ignored. The very first account created is always an
+# admin regardless.
 LEMBAS_ALLOW_SIGNUP=true
 
 # Default theme for signed-out visitors: moria (dark) or shire (light).

CLAUDE.md

@@ -132,6 +132,12 @@ as parameters for exactly this reason.
 two marks on one page with identical ids make the second silently reuse the
 first one's gradients.
 
+**Two kinds of settings.** `lembas.config` is deployment configuration read
+from the environment at startup. `services/settings_store.py` is instance
+settings an admin edits at runtime, stored in the `settings` table. Environment
+variables seed the latter as an *initial* value only — once stored, the database
+wins, or a toggle in the UI would silently revert on the next restart.
+
 **JSON columns need reassignment.** `user.settings_json["theme"] = x` on a
 plain dict is not detected. The columns use `MutableDict` (`db/types.py`), but
 the safe habit is `obj.field = {**obj.field, "k": v}`.
@@ -165,10 +171,14 @@ inlined and themed. If the mark changes, update both.
 
 ## Deployment
 
-`deploy/` holds the systemd unit and nginx vhost for the gamebox install at
+`deploy/` holds a systemd unit template, an nginx vhost template, and
-`https://chat.lan`. See `deploy/README.md`. Service user `lembas`, home
+install/update scripts. Both templates are parameterised (`__PREFIX__`,
-`/home/lembas` bind-mounted to `/srv/lembas`, mirroring the llama-swap and
+`__SITE_HOST__`, …) and substituted at install time, so nothing host-specific is
-comfyui conventions on that machine.
+committed here. See `deploy/README.md`.
+
+This repository is **public**. Keep deployment-specific hostnames, ports and
+internal infrastructure detail out of it — those belong in whatever private
+notes describe the machine.
 
 ## Not built yet
 

README.md

@@ -37,7 +37,9 @@ runtime. Clone it, `pip install -e .`, run it.
 - **OpenAI connections** — point at OpenAI, LM Studio, vLLM, llama.cpp,
   llama-swap, Ollama or OpenRouter; models are discovered and cached
 - **Accounts** — first account becomes the administrator, argon2 password
-  hashing, revocable server-side sessions
+  hashing, revocable server-side sessions, self-service password change
+- **Admin settings** — open or close registration from the UI, stored in the
+  database and effective immediately
 - **Two themes** — *Moria* (dark) and *Shire* (light), switchable per user
 
 **Planned**
@@ -80,7 +82,7 @@ All variables are prefixed `LEMBAS_` and can live in `.env`. See
 | `LEMBAS_SECRET_KEY` | *generated* | Signs sessions and encrypts stored API keys. **Set this.** A generated key changes every restart, signing everyone out and making stored API keys unreadable. |
 | `LEMBAS_DATA_DIR` | `./data` | SQLite database and uploads. |
 | `LEMBAS_HOST` / `LEMBAS_PORT` | `127.0.0.1` / `8080` | Bind address. |
-| `LEMBAS_ALLOW_SIGNUP` | `true` | Let new users register themselves. The first account is always an admin regardless. |
+| `LEMBAS_ALLOW_SIGNUP` | `true` | Whether new users may register themselves — the *initial* value only. Once set under **Admin → General** the stored setting wins. The first account is always an admin regardless. |
 | `LEMBAS_DEFAULT_THEME` | `moria` | `moria` (dark) or `shire` (light). |
 | `LEMBAS_SESSION_TTL` | `2592000` | Session lifetime in seconds. |
 | `LEMBAS_REQUEST_TIMEOUT` | `300` | Seconds to wait on an upstream model. |

deploy/README.md

@@ -1,51 +1,63 @@
 # Deployment
 
-Installs LLeMbas as a **system** service behind nginx at `https://chat.lan`.
+Installs LLeMbas as a **system** service behind nginx with a self-signed
+certificate. Written for a systemd + nginx host; tested on Arch.
 
-Written for `gamebox` (Arch), and follows the conventions already used there
+| | Default |
-for llama-swap and comfyui:
-
-| | |
 |---|---|
 | Service user | `lembas` (system account, `nologin`) |
-| Home | `/home/lembas`, bind-mounted to `/srv/lembas` |
+| Home | `/home/lembas` |
-| Checkout | `/srv/lembas/app` (git clone of the Gitea remote) |
+| Install prefix | `/srv/lembas` (bind mount of the home) |
-| Virtualenv | `/srv/lembas/venv` |
+| Checkout | `$PREFIX/app` |
-| Database | `/srv/lembas/data/lembas.db` |
+| Virtualenv | `$PREFIX/venv` |
-| Environment | `/srv/lembas/lembas.env` (mode 600) |
+| Database | `$PREFIX/data/lembas.db` |
+| Environment | `$PREFIX/lembas.env` (mode 600) |
 | Unit | `/etc/systemd/system/lembas.service` |
-| Vhost | `/etc/nginx/conf.d/chat.lan.conf`, self-signed cert |
+| Vhost | `/etc/nginx/conf.d/<host>.conf` |
-| Listens | `127.0.0.1:8080` — reachable only through nginx |
+| Listens on | `127.0.0.1:8080` — reachable only through nginx |
 
-The home lives on `/home` rather than `/var/lib` because the root LV on that
+The prefix defaults to a bind mount of the service user's home because on many
-box is only 50 GB; `/srv/lembas` is the same bind-mount trick as `/srv/llama`
+machines the root filesystem is small while `/home` is not, and the virtualenv
-and `/srv/comfyui`.
+plus database belong on the larger volume. Set `PREFIX=$HOME_DIR` to skip it.
 
 ## First install
 
 ```bash
-./deploy/install.sh
+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
+repo, builds the venv, generates `lembas.env` with a fresh `LEMBAS_SECRET_KEY`,
-`LEMBAS_SECRET_KEY`, installs the unit and vhost, issues a self-signed cert,
+installs the unit and vhost, issues a self-signed certificate, adds a
-adds a `/etc/hosts` entry, and enables the service.
+`/etc/hosts` entry if the name does not already resolve, and enables the
+service.
 
-Then open <https://chat.lan>, accept the self-signed certificate warning, and
+Then open `https://<SITE_HOST>`, accept the certificate warning, and create the
-create the first account — it becomes the administrator.
+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
 
 ```bash
-git push          # from the working copy
+git push
 ./deploy/update.sh
 ```
 
-`update.sh` fetches, hard-resets `/srv/lembas/app` to `origin/main`, reinstalls
+`update.sh` fetches, hard-resets the deployment checkout to `origin/main`,
-dependencies and restarts the service, then prints what changed. The hard reset
+reinstalls dependencies and restarts, printing the commits it pulled. The hard
-is deliberate: nothing is ever edited in place there, so there is no local work
+reset is deliberate: nothing is ever edited in place there, so there is no local
-to preserve and no merge conflicts to resolve.
+work to preserve and no conflicts to resolve.
 
 ## Operating it
 
@@ -53,10 +65,9 @@ to preserve and no merge conflicts to resolve.
 systemctl status lembas
 journalctl -u lembas -f
 sudo -u lembas /srv/lembas/venv/bin/lembas info      # paths and counts
-sudo systemctl restart lembas
 ```
 
-Configuration lives in `/srv/lembas/lembas.env`. Edit it and restart.
+Configuration lives in `$PREFIX/lembas.env`. Edit it and restart.
 
 ## Notes
 
@@ -70,11 +81,10 @@ 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.
 
-**Name resolution.** `chat.lan` is in Pi-hole, but this box queries the router
-first and the router's dnsmasq is authoritative for `.lan` without forwarding
-those queries on — the same reason `comfy.lan` needs one. `install.sh` adds a
-`/etc/hosts` entry, which is harmless if DNS already answers.
-
 **Hardening is deliberately moderate.** `ProtectSystem=full`, not `strict`: the
 agentic features planned for later need to run commands, and a lockdown that
 has to be torn out again is worse than one that was never applied.
+
+**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.

deploy/install.sh

@@ -1,28 +1,52 @@
 #!/usr/bin/env bash
-# Install LLeMbas as a system service behind nginx at https://chat.lan.
+# Install LLeMbas as a system service behind nginx with a self-signed cert.
 #
-# Follows the conventions already used on this box for llama-swap and comfyui:
+# Creates a dedicated service user, a virtualenv, a systemd unit and an nginx
-# a dedicated service user whose home lives on /home (the root LV is only
+# vhost. Idempotent: safe to re-run. To deploy new code afterwards use
-# 50 GB) and is bind-mounted to /srv/<name>, a system unit so it survives
+# update.sh, which is what a `git push` should be followed by.
-# logout, and an nginx vhost with a self-signed cert.
 #
-# Idempotent: safe to re-run. To deploy new code afterwards use update.sh,
+# Everything is configurable from the environment:
-# which is what a `git push` should be followed by.
+#
+#   SITE_HOST=chat.example   ./deploy/install.sh    # vhost name
+#   APP_PORT=8080                                   # loopback port
+#   PREFIX=/srv/lembas                              # install root
+#   HOME_DIR=/home/lembas                           # service user's home
+#   REPO_URL=...                                    # defaults to this checkout's origin
+#
+# PREFIX defaults to a bind mount of HOME_DIR rather than living directly under
+# /srv, because on many machines the root filesystem is small and the venv plus
+# database belong on the larger /home volume. Set PREFIX=HOME_DIR to skip that.
 set -euo pipefail
 
-REPO_URL="${LEMBAS_REPO_URL:-https://git.houmeres.sk/Houmeres/LLeMbas.git}"
+HERE="$(dirname "$(readlink -f "$0")")"
+
+SITE_HOST="${SITE_HOST:-lembas.local}"
+APP_PORT="${APP_PORT:-8080}"
+SERVICE_USER="${SERVICE_USER:-lembas}"
+HOME_DIR="${HOME_DIR:-/home/lembas}"
+PREFIX="${PREFIX:-/srv/lembas}"
 BRANCH="${LEMBAS_BRANCH:-main}"
-SERVICE_USER=lembas
+# Default to wherever this checkout came from, so a fork deploys itself.
-HOME_DIR=/home/lembas
+REPO_URL="${REPO_URL:-$(git -C "$HERE" remote get-url origin 2>/dev/null || true)}"
-PREFIX=/srv/lembas
+
 APP="$PREFIX/app"
 VENV="$PREFIX/venv"
 ENV_FILE="$PREFIX/lembas.env"
-HERE="$(dirname "$(readlink -f "$0")")"
+
+if [[ -z "$REPO_URL" ]]; then
+  echo "Could not determine REPO_URL. Set it explicitly." >&2
+  exit 1
+fi
+
+echo "== plan =="
+echo "   host    : https://$SITE_HOST  ->  127.0.0.1:$APP_PORT"
+echo "   user    : $SERVICE_USER ($HOME_DIR)"
+echo "   prefix  : $PREFIX"
+echo "   repo    : $REPO_URL ($BRANCH)"
 
 echo "== service user =="
 # --system: no ageing, no mail spool. Home under /home, not /var/lib, so the
-# venv and database sit on the big volume.
+# venv and database sit on the larger volume.
 if ! getent passwd "$SERVICE_USER" >/dev/null; then
   sudo useradd --system --create-home --home-dir "$HOME_DIR" \
        --shell /usr/bin/nologin --comment "LLeMbas" "$SERVICE_USER"
@@ -31,12 +55,14 @@ else
 fi
 sudo chmod 755 "$HOME_DIR"
 
-echo "== /srv/lembas bind-mount onto /home =="
+if [[ "$PREFIX" != "$HOME_DIR" ]]; then
+  echo "== $PREFIX bind-mount onto $HOME_DIR =="
   sudo mkdir -p "$PREFIX"
   grep -q "^$HOME_DIR[[:space:]]" /etc/fstab \
     || echo "$HOME_DIR  $PREFIX  none  bind  0 0" | sudo tee -a /etc/fstab >/dev/null
   sudo systemctl daemon-reload
   mountpoint -q "$PREFIX" || sudo mount "$PREFIX"
+fi
 
 echo "== checkout =="
 if [[ ! -d "$APP/.git" ]]; then
@@ -53,8 +79,8 @@ sudo -u "$SERVICE_USER" "$VENV/bin/pip" install --quiet --upgrade pip
 sudo -u "$SERVICE_USER" "$VENV/bin/pip" install --quiet -e "$APP"
 
 echo "== environment =="
-# Generated once and never regenerated: rotating LEMBAS_SECRET_KEY would sign
+# Generated once and never regenerated: rotating LEMBAS_SECRET_KEY signs every
-# every user out and make the stored API keys unreadable.
+# user out AND makes the stored upstream API keys unreadable.
 if [[ ! -f "$ENV_FILE" ]]; then
   KEY=$("$VENV/bin/python" -c "import secrets; print(secrets.token_urlsafe(48))")
   sudo tee "$ENV_FILE" >/dev/null <<EOF
@@ -63,9 +89,9 @@ if [[ ! -f "$ENV_FILE" ]]; then
 # Changing it signs everyone out and makes stored API keys unreadable.
 LEMBAS_SECRET_KEY=$KEY
 LEMBAS_DATA_DIR=$PREFIX/data
-# Loopback only: reachable through the nginx chat.lan vhost, never direct.
+# Loopback only: reachable through the nginx vhost, never directly.
 LEMBAS_HOST=127.0.0.1
-LEMBAS_PORT=8080
+LEMBAS_PORT=$APP_PORT
 LEMBAS_LOG_LEVEL=info
 LEMBAS_ALLOW_SIGNUP=true
 LEMBAS_DEFAULT_THEME=moria
@@ -80,30 +106,34 @@ fi
 sudo install -d -o "$SERVICE_USER" -g "$SERVICE_USER" -m 750 "$PREFIX/data"
 
 echo "== systemd unit =="
-sudo install -Dm644 "$HERE/lembas.service" /etc/systemd/system/lembas.service
+sed -e "s|__PREFIX__|$PREFIX|g" -e "s|__SERVICE_USER__|$SERVICE_USER|g" \
+    "$HERE/lembas.service" | sudo tee /etc/systemd/system/lembas.service >/dev/null
 sudo systemctl daemon-reload
 
-echo "== self-signed cert for chat.lan =="
+echo "== self-signed cert for $SITE_HOST =="
 sudo mkdir -p /etc/nginx/ssl
-if [[ ! -f /etc/nginx/ssl/chat.lan.crt ]]; then
+if [[ ! -f "/etc/nginx/ssl/$SITE_HOST.crt" ]]; then
   sudo openssl req -x509 -newkey rsa:2048 -nodes \
-    -keyout /etc/nginx/ssl/chat.lan.key -out /etc/nginx/ssl/chat.lan.crt \
+    -keyout "/etc/nginx/ssl/$SITE_HOST.key" -out "/etc/nginx/ssl/$SITE_HOST.crt" \
-    -days 3650 -subj "/CN=chat.lan" -addext "subjectAltName=DNS:chat.lan"
+    -days 3650 -subj "/CN=$SITE_HOST" -addext "subjectAltName=DNS:$SITE_HOST"
-  sudo chmod 600 /etc/nginx/ssl/chat.lan.key
+  sudo chmod 600 "/etc/nginx/ssl/$SITE_HOST.key"
-  sudo chmod 644 /etc/nginx/ssl/chat.lan.crt
+  sudo chmod 644 "/etc/nginx/ssl/$SITE_HOST.crt"
 fi
 
 echo "== nginx vhost =="
-sudo install -Dm644 "$HERE/chat.lan.nginx.conf" /etc/nginx/conf.d/chat.lan.conf
+sed -e "s|__SITE_HOST__|$SITE_HOST|g" -e "s|__APP_PORT__|$APP_PORT|g" \
+    "$HERE/nginx-vhost.conf" | sudo tee "/etc/nginx/conf.d/$SITE_HOST.conf" >/dev/null
 sudo nginx -t
 sudo systemctl reload nginx
 
 echo "== local name resolution =="
-# chat.lan is in Pi-hole, but this box asks the router first and the router's
+# Only useful when the LAN's DNS does not already answer for this name.
-# dnsmasq is authoritative for .lan without forwarding it on -- same reason
+if ! getent hosts "$SITE_HOST" >/dev/null; then
-# comfy.lan needs a hosts entry. Harmless if DNS already resolves it.
+  printf '127.0.0.1\t%s\n::1\t\t%s\n' "$SITE_HOST" "$SITE_HOST" | sudo tee -a /etc/hosts >/dev/null
-grep -q 'chat\.lan' /etc/hosts \
+  echo "   added $SITE_HOST to /etc/hosts"
-  || printf '127.0.0.1\tchat.lan\n::1\t\tchat.lan\n' | sudo tee -a /etc/hosts >/dev/null
+else
+  echo "   $SITE_HOST already resolves"
+fi
 
 echo "== enable service =="
 sudo systemctl enable --now lembas
@@ -111,5 +141,5 @@ sleep 2
 sudo systemctl --no-pager --lines=0 status lembas || true
 
 echo
-echo "LLeMbas is up at https://chat.lan  (self-signed cert; accept the warning)"
+echo "LLeMbas is up at https://$SITE_HOST  (self-signed cert; accept the warning)"
 echo "Create the first account -- it becomes the administrator."

deploy/lembas.service

@@ -1,48 +1,43 @@
-# LLeMbas system service.
+# LLeMbas system service template.
 #
-# Deployed to /etc/systemd/system/lembas.service by deploy/install.sh.
+# install.sh substitutes __PREFIX__ and __SERVICE_USER__ and writes the result
+# to /etc/systemd/system/lembas.service. Edit this file, not the installed copy.
 #
 # A system unit, not a user unit, so it survives logout and comes up at boot
-# without anyone signing in -- matching llama-swap and comfyui on this box.
+# without anyone signing in.
-#
-# /srv/lembas is a bind mount of /home/lembas: the root LV is only 50 GB and
-# the venv plus SQLite database belong on /home, same trick as /srv/llama.
 
 [Unit]
 Description=LLeMbas - web UI for language models
-Documentation=https://git.houmeres.sk/Houmeres/LLeMbas
 After=network-online.target
 Wants=network-online.target
-# The unit is useless without the bind mount: the venv and database live there.
+# The prefix is usually a bind mount; the venv and database live there, so
-RequiresMountsFor=/srv/lembas
+# starting before it is mounted would create an empty database in its place.
-# Not a hard dependency. LLeMbas starts fine with the endpoint down and shows a
+RequiresMountsFor=__PREFIX__
-# readable error in the admin UI, which is better than refusing to boot.
-After=llama-swap.service
 
 [Service]
 Type=simple
-User=lembas
+User=__SERVICE_USER__
-Group=lembas
+Group=__SERVICE_USER__
-WorkingDirectory=/srv/lembas/app
+WorkingDirectory=__PREFIX__/app
-EnvironmentFile=/srv/lembas/lembas.env
+EnvironmentFile=__PREFIX__/lembas.env
-ExecStart=/srv/lembas/venv/bin/lembas serve
+ExecStart=__PREFIX__/venv/bin/lembas serve
 Restart=on-failure
 RestartSec=5
 
-# Reachable only through the nginx chat.lan vhost, never directly on the LAN.
+# The bind address comes from LEMBAS_HOST in the environment file, which the
-# The bind address is set by LEMBAS_HOST in the environment file.
+# installer sets to 127.0.0.1: reachable through nginx, never directly.
 
 # --- Hardening -------------------------------------------------------------
-# Modest rather than maximal: the agentic features planned for later will need
+# Moderate rather than maximal. The agentic features planned for later need to
-# to run commands, so ProtectSystem=strict would only be torn out again.
+# run commands, and a lockdown that has to be torn out again is worse than one
+# that was never applied.
 NoNewPrivileges=yes
 PrivateTmp=yes
 ProtectSystem=full
 ProtectKernelTunables=yes
 ProtectControlGroups=yes
 RestrictSUIDSGID=yes
-# Only /srv/lembas needs to be writable; /home/lembas is the same inode.
+ReadWritePaths=__PREFIX__
-ReadWritePaths=/srv/lembas
 LimitNOFILE=65535
 
 [Install]

deploy/nginx-vhost.conf

@@ -1,12 +1,16 @@
-# chat.lan - HTTPS reverse proxy to LLeMbas (127.0.0.1:8080).
+# nginx vhost template for LLeMbas.
-# Deployed to /etc/nginx/conf.d/chat.lan.conf. Self-signed cert (chat.lan).
 #
-# Mirrors the comfy.lan and llama.lan vhosts on this box.
+# install.sh substitutes __SITE_HOST__ and __APP_PORT__ and writes the result to
+# /etc/nginx/conf.d/<host>.conf. Edit this file, not the installed copy.
+#
+# Assumes a self-signed certificate at /etc/nginx/ssl/<host>.{crt,key}, which
+# install.sh generates. To use a real certificate, point ssl_certificate at it;
+# nothing else here needs to change.
 
 server {
     listen 80;
     listen [::]:80;
-    server_name chat.lan;
+    server_name __SITE_HOST__;
     return 301 https://$host$request_uri;
 }
 
@@ -14,17 +18,17 @@ server {
     listen 443 ssl;
     listen [::]:443 ssl;
     http2 on;
-    server_name chat.lan;
+    server_name __SITE_HOST__;
 
-    ssl_certificate     /etc/nginx/ssl/chat.lan.crt;
+    ssl_certificate     /etc/nginx/ssl/__SITE_HOST__.crt;
-    ssl_certificate_key /etc/nginx/ssl/chat.lan.key;
+    ssl_certificate_key /etc/nginx/ssl/__SITE_HOST__.key;
     ssl_protocols       TLSv1.2 TLSv1.3;
 
     # File uploads land here once that feature exists; 0 = no limit.
     client_max_body_size 0;
 
     location / {
-        proxy_pass http://127.0.0.1:8080;
+        proxy_pass http://127.0.0.1:__APP_PORT__;
         proxy_http_version 1.1;
         proxy_set_header Host              $host;
         proxy_set_header X-Real-IP         $remote_addr;
@@ -32,13 +36,14 @@ server {
         proxy_set_header X-Forwarded-Proto $scheme;
 
         # Streamed replies are server-sent events. Every one of these matters:
-        # with buffering on, nginx holds the whole reply and delivers it in one
+        # with buffering on (the default) nginx holds the whole reply and
-        # lump at the end, which looks exactly like streaming being broken.
+        # delivers it in one lump at the end, which is indistinguishable from
+        # streaming being broken.
         proxy_buffering         off;
         proxy_request_buffering off;
         proxy_cache             off;
-        # SSE is plain HTTP/1.1 chunked, so the connection header must not be
+        # SSE is plain HTTP/1.1 chunked, not a websocket upgrade, so the
-        # the websocket upgrade dance -- it must simply stay open.
+        # connection header must simply be left to keep-alive.
         proxy_set_header Connection "";
 
         # A model can think for minutes before the first token. The default
@@ -47,9 +52,8 @@ server {
         proxy_send_timeout 3600s;
     }
 
-    # Static assets are immutable per release and never need revalidating.
     location /static/ {
-        proxy_pass http://127.0.0.1:8080;
+        proxy_pass http://127.0.0.1:__APP_PORT__;
         proxy_set_header Host $host;
         expires 1h;
         add_header Cache-Control "public";

deploy/update.sh

@@ -1,36 +1,39 @@
 #!/usr/bin/env bash
-# Pull the latest LLeMbas and restart the service.
+# Pull the latest LLeMbas into the deployment and restart the service.
 #
-# This is what to run after pushing: it fetches, hard-resets the deployment
+# Run this after pushing. It fetches, hard-resets the deployment checkout to the
-# checkout to the remote branch, reinstalls dependencies if they changed, and
+# remote branch, reinstalls dependencies if they changed, and restarts. Nothing
-# restarts. Nothing is ever edited in place at /srv/lembas/app, so a hard reset
+# is ever edited in place under the deployment prefix, so a hard reset is safe
-# is safe and avoids merge conflicts from a dirty deployment tree.
+# and avoids merge conflicts from a dirty tree.
 set -euo pipefail
 
-SERVICE_USER=lembas
+SERVICE_USER="${SERVICE_USER:-lembas}"
-PREFIX=/srv/lembas
+PREFIX="${PREFIX:-/srv/lembas}"
+BRANCH="${LEMBAS_BRANCH:-main}"
+
 APP="$PREFIX/app"
 VENV="$PREFIX/venv"
-BRANCH="${LEMBAS_BRANCH:-main}"
 
 if [[ ! -d "$APP/.git" ]]; then
   echo "No deployment at $APP. Run deploy/install.sh first." >&2
   exit 1
 fi
 
-before=$(sudo -u "$SERVICE_USER" git -C "$APP" rev-parse HEAD)
+git_as() { sudo -u "$SERVICE_USER" git -C "$APP" "$@"; }
+
+before=$(git_as rev-parse HEAD)
 
 echo "== fetching =="
-sudo -u "$SERVICE_USER" git -C "$APP" fetch --quiet origin "$BRANCH"
+git_as fetch --quiet origin "$BRANCH"
-sudo -u "$SERVICE_USER" git -C "$APP" reset --hard --quiet "origin/$BRANCH"
+git_as reset --hard --quiet "origin/$BRANCH"
 
-after=$(sudo -u "$SERVICE_USER" git -C "$APP" rev-parse HEAD)
+after=$(git_as rev-parse HEAD)
 
 if [[ "$before" == "$after" ]]; then
-  echo "   already at $(git -C "$APP" rev-parse --short HEAD), nothing to pull"
+  echo "   already at ${after:0:7}, nothing to pull"
 else
-  echo "   $(echo "$before" | cut -c1-7) -> $(echo "$after" | cut -c1-7)"
+  echo "   ${before:0:7} -> ${after:0:7}"
-  sudo -u "$SERVICE_USER" git -C "$APP" --no-pager log --oneline "$before..$after" | sed 's/^/     /'
+  git_as --no-pager log --oneline "$before..$after" | sed 's/^/     /'
 fi
 
 # Cheap and idempotent; catches a dependency added since the last deploy.
@@ -42,7 +45,7 @@ sudo systemctl restart lembas
 sleep 2
 
 if systemctl is-active --quiet lembas; then
-  echo "   lembas is running at https://chat.lan"
+  echo "   lembas is running"
 else
   echo "   lembas FAILED to start:" >&2
   sudo journalctl -u lembas -n 30 --no-pager >&2

src/lembas/api/admin.py

@@ -11,7 +11,8 @@ from sqlalchemy import func, select
 from sqlalchemy.orm import Session as DBSession
 
 from lembas.api.deps import AdminUser, Db
-from lembas.db.models import Connection, Model
+from lembas.db.models import Connection, Model, User
+from lembas.services import settings_store
 from lembas.services.crypto import decrypt, encrypt, mask
 from lembas.services.llm.openai_client import Endpoint, LLMError, list_models
 from lembas.web.templating import render
@@ -39,7 +40,43 @@ def _connections(db: DBSession) -> list[Connection]:
 
 @router.get("")
 async def admin_home(user: AdminUser):
-    return RedirectResponse("/admin/connections", status_code=status.HTTP_303_SEE_OTHER)
+    return RedirectResponse("/admin/general", status_code=status.HTTP_303_SEE_OTHER)
+
+
+@router.get("/general")
+async def general_page(request: Request, db: Db, user: AdminUser, saved: bool = False):
+    return render(
+        request,
+        "admin/general.html",
+        {
+            "values": settings_store.get_group(db),
+            "saved": saved,
+            "user_count": db.scalar(select(func.count()).select_from(User)),
+        },
+    )
+
+
+@router.post("/general")
+async def save_general(
+    db: Db,
+    user: AdminUser,
+    instance_name: str = Form("LLeMbas"),
+    allow_signup: bool = Form(False),
+) -> Response:
+    """Save instance settings.
+
+    Unchecked checkboxes are simply absent from a form post, which is why
+    allow_signup defaults to False here -- that absence *is* the "off" signal.
+    """
+    settings_store.update(
+        db,
+        {
+            "instance_name": instance_name.strip()[:120] or "LLeMbas",
+            "allow_signup": allow_signup,
+        },
+    )
+    log.info("registration %s by %s", "opened" if allow_signup else "closed", user.email)
+    return RedirectResponse("/admin/general?saved=1", status_code=status.HTTP_303_SEE_OTHER)
 
 
 @router.get("/connections")

src/lembas/api/auth.py

@@ -13,6 +13,7 @@ from lembas.config import settings
 from lembas.db.models import ROLE_ADMIN, ROLE_USER, User
 from lembas.security.passwords import hash_password, validate_password, verify_password
 from lembas.security.sessions import COOKIE_NAME, create_session, revoke_session
+from lembas.services import settings_store
 from lembas.web.templating import render
 
 log = logging.getLogger(__name__)
@@ -48,6 +49,19 @@ def _safe_next(raw: str | None) -> str:
     return raw
 
 
+def _login_page(request: Request, db: Db, *, status_code: int = 200, **context):
+    """Render the sign-in page.
+
+    Always goes through here so `allow_signup` reflects the *stored* setting
+    rather than the environment default baked in by render(). Otherwise the
+    "Create one" link would keep appearing after an administrator closed
+    registration, offering a link that only leads to a refusal.
+    """
+    context.setdefault("next", "/")
+    context["allow_signup"] = settings_store.signup_allowed(db)
+    return render(request, "auth/login.html", context, status_code=status_code)
+
+
 @router.get("/login")
 async def login_form(request: Request, db: Db, user: CurrentUser, next: str = "/"):
     if user is not None:
@@ -57,7 +71,7 @@ async def login_form(request: Request, db: Db, user: CurrentUser, next: str = "/
     # cannot possibly satisfy.
     if _no_users_yet(db):
         return RedirectResponse("/auth/register", status_code=status.HTTP_303_SEE_OTHER)
-    return render(request, "auth/login.html", {"next": _safe_next(next)})
+    return _login_page(request, db, next=_safe_next(next))
 
 
 @router.post("/login")
@@ -75,21 +89,23 @@ async def login(
     # cannot be used to discover which addresses are registered.
     if user is None or not verify_password(password, user.password_hash):
         log.info("failed sign-in for %s", email)
-        return render(
+        return _login_page(
             request,
-            "auth/login.html",
+            db,
-            {"error": "That email and password do not match.", "email": email,
-             "next": _safe_next(next)},
             status_code=status.HTTP_401_UNAUTHORIZED,
+            error="That email and password do not match.",
+            email=email,
+            next=_safe_next(next),
         )
 
     if not user.active:
-        return render(
+        return _login_page(
             request,
-            "auth/login.html",
+            db,
-            {"error": "This account has been deactivated. Ask an administrator.",
-             "email": email, "next": _safe_next(next)},
             status_code=status.HTTP_403_FORBIDDEN,
+            error="This account has been deactivated. Ask an administrator.",
+            email=email,
+            next=_safe_next(next),
         )
 
     token = create_session(
@@ -108,12 +124,12 @@ async def register_form(request: Request, db: Db, user: CurrentUser):
     if user is not None:
         return RedirectResponse("/", status_code=status.HTTP_303_SEE_OTHER)
     first_run = _no_users_yet(db)
-    if not first_run and not settings.allow_signup:
+    if not first_run and not settings_store.signup_allowed(db):
-        return render(
+        return _login_page(
             request,
-            "auth/login.html",
+            db,
-            {"error": "Registration is closed. Ask an administrator for an account."},
             status_code=status.HTTP_403_FORBIDDEN,
+            error="Registration is closed. Ask an administrator for an account.",
         )
     return render(request, "auth/register.html", {"first_run": first_run})
 
@@ -127,12 +143,12 @@ async def register(
     password: str = Form(...),
 ):
     first_run = _no_users_yet(db)
-    if not first_run and not settings.allow_signup:
+    if not first_run and not settings_store.signup_allowed(db):
-        return render(
+        return _login_page(
             request,
-            "auth/login.html",
+            db,
-            {"error": "Registration is closed. Ask an administrator for an account."},
             status_code=status.HTTP_403_FORBIDDEN,
+            error="Registration is closed. Ask an administrator for an account.",
         )
 
     name = name.strip()

src/lembas/api/pages.py

@@ -97,13 +97,23 @@ async def chat_detail(request: Request, db: Db, user: RequiredUser, chat_id: str
 
 
 @router.get("/settings")
-async def settings_page(request: Request, db: Db, user: RequiredUser):
+async def settings_page(
+    request: Request,
+    db: Db,
+    user: RequiredUser,
+    error: str = "",
+    saved: str = "",
+):
+    # error/saved arrive as query parameters because the password form redirects
+    # back here: a POST that re-rendered in place would re-submit on refresh.
     return render(
         request,
         "settings.html",
         {
             "chat": None,
             "models": chat_service.available_models(db),
+            "error": error,
+            "saved": saved,
             **_sidebar_context(db, user),
         },
     )

src/lembas/api/preferences.py

@@ -2,9 +2,17 @@
 
 from __future__ import annotations
 
-from fastapi import APIRouter, Body
+import logging
+
+from fastapi import APIRouter, Body, Form, Request, status
+from fastapi.responses import RedirectResponse, Response
 
 from lembas.api.deps import Db, RequiredUser
+from lembas.config import settings
+from lembas.security.passwords import hash_password, validate_password, verify_password
+from lembas.security.sessions import COOKIE_NAME, create_session, revoke_all_for_user
+
+log = logging.getLogger(__name__)
 
 router = APIRouter(prefix="/api/preferences", tags=["preferences"])
 
@@ -27,3 +35,68 @@ async def set_theme(db: Db, user: RequiredUser, theme: str = Body(..., embed=Tru
     user.settings_json = {**(user.settings_json or {}), "theme": theme}
     db.commit()
     return {"ok": True, "theme": theme}
+
+
+@router.post("/password")
+async def change_password(
+    request: Request,
+    db: Db,
+    user: RequiredUser,
+    current_password: str = Form(...),
+    new_password: str = Form(...),
+    confirm_password: str = Form(...),
+) -> Response:
+    """Change your own password.
+
+    Every other session is revoked on success. If the reason for changing a
+    password is that someone else knows it, leaving their session alive would
+    defeat the point.
+    """
+
+    def back(message: str, ok: bool = False) -> Response:
+        from urllib.parse import quote
+
+        field = "saved" if ok else "error"
+        return RedirectResponse(
+            f"/settings?{field}={quote(message)}", status_code=status.HTTP_303_SEE_OTHER
+        )
+
+    if not verify_password(current_password, user.password_hash):
+        log.info("failed password change for %s: current password wrong", user.email)
+        return back("Your current password is not correct.")
+
+    if new_password != confirm_password:
+        return back("The new passwords do not match.")
+
+    if (problem := validate_password(new_password)) is not None:
+        return back(problem)
+
+    if verify_password(new_password, user.password_hash):
+        return back("That is already your password.")
+
+    user.password_hash = hash_password(new_password)
+    db.commit()
+
+    revoke_all_for_user(db, user)
+    token = create_session(
+        db,
+        user,
+        user_agent=request.headers.get("user-agent", ""),
+        ip_address=request.client.host if request.client else "",
+    )
+    log.info("password changed for %s; other sessions revoked", user.email)
+
+    # revoke_all_for_user killed this session too, so hand back a fresh cookie
+    # -- otherwise changing your password would sign you out of the tab you are
+    # standing in.
+    response = back("Password changed. Any other sessions have been signed out.", ok=True)
+    response.set_cookie(
+        COOKIE_NAME,
+        token,
+        max_age=settings.session_ttl,
+        httponly=True,
+        samesite="lax",
+        secure=False,
+        path="/",
+    )
+    return response

src/lembas/services/settings_store.py

@@ -0,0 +1,63 @@
+"""Instance-wide settings that administrators can change at runtime.
+
+Distinct from ``lembas.config``, which holds deployment configuration read from
+the environment at startup. Anything here is editable from the admin UI and
+lives in the ``settings`` table.
+
+Environment variables act as the *initial* value only. Once an administrator
+sets something in the UI, the stored value wins -- otherwise a toggle in the
+interface would silently revert on the next restart, which is worse than not
+offering the toggle at all.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+from sqlalchemy.orm import Session as DBSession
+
+from lembas.config import settings as env_settings
+from lembas.db.models import Setting
+
+GENERAL = "general"
+
+
+def _defaults() -> dict[str, Any]:
+    return {
+        "allow_signup": env_settings.allow_signup,
+        # When on, new accounts land in the `pending` role and cannot sign in
+        # until an administrator approves them. Reserved for the users pass.
+        "require_approval": False,
+        "instance_name": "LLeMbas",
+    }
+
+
+def get_group(db: DBSession, key: str = GENERAL) -> dict[str, Any]:
+    """Stored settings for a group, with defaults filled in for absent keys."""
+    values = _defaults() if key == GENERAL else {}
+    row = db.get(Setting, key)
+    if row is not None and isinstance(row.value, dict):
+        values.update(row.value)
+    return values
+
+
+def get(db: DBSession, name: str, *, key: str = GENERAL) -> Any:
+    return get_group(db, key).get(name)
+
+
+def update(db: DBSession, changes: dict[str, Any], *, key: str = GENERAL) -> dict[str, Any]:
+    """Merge changes into a settings group and persist them."""
+    row = db.get(Setting, key)
+    if row is None:
+        row = Setting(key=key, value={})
+        db.add(row)
+
+    # Reassigned rather than mutated: SQLAlchemy only reliably detects a change
+    # to a JSON column when the whole value is replaced.
+    row.value = {**(row.value or {}), **changes}
+    db.commit()
+    return get_group(db, key)
+
+
+def signup_allowed(db: DBSession) -> bool:
+    return bool(get(db, "allow_signup"))

src/lembas/web/templates/admin/_layout.html

@@ -22,6 +22,10 @@
     <nav class="sidebar__scroll" aria-label="Administration">
       <div class="nav-group">
         <div class="nav-group__label">Administration</div>
+        <a class="nav-item {{ 'is-active' if section == 'general' }}" href="/admin/general">
+          {{ icon("gear", "icon--sm") }}
+          <span class="nav-item__label">General</span>
+        </a>
         <a class="nav-item {{ 'is-active' if section == 'connections' }}"
            href="/admin/connections">
           {{ icon("server", "icon--sm") }}
@@ -40,7 +44,7 @@
           <span class="nav-item__label">Users &amp; groups</span>
         </span>
         <span class="nav-item is-disabled">
-          {{ icon("gear", "icon--sm") }}
+          {{ icon("sliders", "icon--sm") }}
           <span class="nav-item__label">Tools</span>
         </span>
       </div>

src/lembas/web/templates/admin/general.html

@@ -0,0 +1,74 @@
+{% extends "admin/_layout.html" %}
+{% from "_macros.html" import icon %}
+{% set section = "general" %}
+
+{% block title %}General - LLeMbas{% endblock %}
+{% block heading %}General{% endblock %}
+
+{% block admin_content %}
+<p class="admin-lede">
+  Instance-wide settings. These are stored in the database and take effect
+  immediately — no restart, and they survive one.
+</p>
+
+{% if saved %}
+<div class="alert alert--success">{{ icon("check", "icon--sm") }} <span>Settings saved.</span></div>
+{% endif %}
+
+<form method="post" action="/admin/general">
+  <section class="card">
+    <h2 class="card__title">Identity</h2>
+    <div class="field">
+      <label class="field__label" for="instance-name">Instance name</label>
+      <input class="input" id="instance-name" name="instance_name"
+             value="{{ values.instance_name }}" maxlength="120">
+      <p class="field__hint">Shown in the browser tab and on the sign-in page.</p>
+    </div>
+  </section>
+
+  <section class="card">
+    <h2 class="card__title">
+      Registration
+      {% if values.allow_signup %}
+      <span class="badge badge--success">open</span>
+      {% else %}
+      <span class="badge badge--danger">closed</span>
+      {% endif %}
+    </h2>
+
+    <div class="field">
+      <label class="checkbox">
+        <input type="checkbox" name="allow_signup" value="true"
+               {{ 'checked' if values.allow_signup }}>
+        <span>Anyone who can reach this instance may create an account</span>
+      </label>
+      <p class="field__hint">
+        Turn this off once your users exist. Sign-in is unaffected — existing
+        accounts keep working, and the "Create one" link disappears from the
+        sign-in page.
+      </p>
+    </div>
+
+    {% if values.allow_signup and user_count > 0 %}
+    <div class="alert alert--warning">
+      {{ icon("warning", "alert__icon") }}
+      <div>
+        <strong>Registration is open.</strong>
+        <div class="text-sm" style="margin-top: var(--sp-1)">
+          This instance has {{ user_count }} account{{ '' if user_count == 1 else 's' }}.
+          Anyone who can reach it can add another, and every account can use your
+          configured models and API keys.
+        </div>
+      </div>
+    </div>
+    {% endif %}
+
+    <p class="field__hint">
+      <code>LEMBAS_ALLOW_SIGNUP</code> in the environment sets only the starting
+      value. Once saved here, this setting wins.
+    </p>
+  </section>
+
+  <button class="btn btn--primary" type="submit">Save settings</button>
+</form>
+{% endblock %}

src/lembas/web/templates/settings.html

@@ -21,6 +21,17 @@
 
     <div class="admin-scroll">
       <div class="admin-page">
+        {% if error %}
+        <div class="alert alert--error" role="alert">
+          {{ icon("warning", "alert__icon") }} <span>{{ error }}</span>
+        </div>
+        {% endif %}
+        {% if saved %}
+        <div class="alert alert--success" role="status">
+          {{ icon("check", "icon--sm") }} <span>{{ saved }}</span>
+        </div>
+        {% endif %}
+
         <section class="card">
           <h2 class="card__title">Account</h2>
           <div class="field">
@@ -55,6 +66,34 @@
           </p>
         </section>
 
+        <section class="card">
+          <h2 class="card__title">Change password</h2>
+          <form method="post" action="/api/preferences/password">
+            <div class="field">
+              <label class="field__label" for="current-password">Current password</label>
+              <input class="input" type="password" id="current-password"
+                     name="current_password" required autocomplete="current-password">
+            </div>
+            <div class="field">
+              <label class="field__label" for="new-password">New password</label>
+              <input class="input" type="password" id="new-password" name="new_password"
+                     required minlength="8" autocomplete="new-password">
+              <p class="field__hint">At least 8 characters.</p>
+            </div>
+            <div class="field">
+              <label class="field__label" for="confirm-password">Confirm new password</label>
+              <input class="input" type="password" id="confirm-password"
+                     name="confirm_password" required minlength="8"
+                     autocomplete="new-password">
+            </div>
+            <button class="btn btn--primary" type="submit">Change password</button>
+            <p class="field__hint" style="margin-top: var(--sp-3)">
+              Every other session is signed out when the password changes. You
+              stay signed in here.
+            </p>
+          </form>
+        </section>
+
         <section class="card">
           <h2 class="card__title">Session</h2>
           <form method="post" action="/auth/logout">

tests/test_settings.py

@@ -0,0 +1,202 @@
+"""Instance settings (registration toggle) and changing your own password."""
+
+from __future__ import annotations
+
+from fastapi.testclient import TestClient
+from sqlalchemy import select
+
+from lembas.db.models import Session as SessionRow
+from lembas.db.models import User
+from lembas.services import settings_store
+
+
+# --- Registration toggle -----------------------------------------------------
+def test_registration_is_open_by_default(client: TestClient, db, registered):
+    assert settings_store.signup_allowed(db) is True
+
+
+def test_closing_registration_blocks_new_accounts(client: TestClient, db, registered):
+    client.post("/admin/general", data={"instance_name": "LLeMbas"}, follow_redirects=False)
+    assert settings_store.signup_allowed(db) is False
+
+    response = client.post(
+        "/auth/register",
+        data={"name": "Uninvited", "email": "no@thanks.test", "password": "let-me-in-please"},
+        follow_redirects=False,
+    )
+    assert response.status_code == 403
+    assert "Registration is closed" in response.text
+    assert db.scalar(select(User).where(User.email == "no@thanks.test")) is None
+
+
+def test_closed_registration_hides_the_create_account_link(
+    client: TestClient, db, registered
+):
+    client.post("/admin/general", data={"instance_name": "LLeMbas"}, follow_redirects=False)
+    client.post("/auth/logout", follow_redirects=False)
+
+    page = client.get("/auth/login")
+    assert "/auth/register" not in page.text
+
+
+def test_open_registration_shows_the_link(client: TestClient, db, registered):
+    client.post(
+        "/admin/general",
+        data={"instance_name": "LLeMbas", "allow_signup": "true"},
+        follow_redirects=False,
+    )
+    client.post("/auth/logout", follow_redirects=False)
+    assert "/auth/register" in client.get("/auth/login").text
+
+
+def test_existing_users_can_still_sign_in_when_registration_is_closed(
+    client: TestClient, db, registered
+):
+    client.post("/admin/general", data={"instance_name": "LLeMbas"}, follow_redirects=False)
+    client.post("/auth/logout", follow_redirects=False)
+
+    response = client.post(
+        "/auth/login",
+        data={"email": registered["email"], "password": registered["password"]},
+        follow_redirects=False,
+    )
+    assert response.status_code == 303
+
+
+def test_stored_setting_beats_the_environment_default(client: TestClient, db, registered):
+    """A toggle that silently reverted on restart would be worse than none."""
+    from lembas.config import settings as env_settings
+
+    assert env_settings.allow_signup is True
+    settings_store.update(db, {"allow_signup": False})
+    assert settings_store.signup_allowed(db) is False
+
+
+def test_ordinary_users_cannot_change_instance_settings(client: TestClient, db, registered):
+    client.post("/auth/logout", follow_redirects=False)
+    client.post(
+        "/auth/register",
+        data={"name": "Sam", "email": "sam@shire.test", "password": "potatoes-po-ta-toes"},
+        follow_redirects=False,
+    )
+    assert client.post("/admin/general", data={"instance_name": "Pwned"}).status_code == 403
+    assert settings_store.get(db, "instance_name") == "LLeMbas"
+
+
+# --- Password change ---------------------------------------------------------
+def test_password_change_works(client: TestClient, db, registered):
+    response = client.post(
+        "/api/preferences/password",
+        data={
+            "current_password": registered["password"],
+            "new_password": "a-much-better-password",
+            "confirm_password": "a-much-better-password",
+        },
+        follow_redirects=False,
+    )
+    assert response.status_code == 303
+    assert "saved=" in response.headers["location"]
+
+    client.post("/auth/logout", follow_redirects=False)
+    assert (
+        client.post(
+            "/auth/login",
+            data={"email": registered["email"], "password": "a-much-better-password"},
+            follow_redirects=False,
+        ).status_code
+        == 303
+    )
+
+
+def test_old_password_stops_working(client: TestClient, db, registered):
+    client.post(
+        "/api/preferences/password",
+        data={
+            "current_password": registered["password"],
+            "new_password": "a-much-better-password",
+            "confirm_password": "a-much-better-password",
+        },
+        follow_redirects=False,
+    )
+    client.post("/auth/logout", follow_redirects=False)
+    assert (
+        client.post(
+            "/auth/login",
+            data={"email": registered["email"], "password": registered["password"]},
+            follow_redirects=False,
+        ).status_code
+        == 401
+    )
+
+
+def test_wrong_current_password_is_refused(client: TestClient, db, registered):
+    response = client.post(
+        "/api/preferences/password",
+        data={
+            "current_password": "not-my-password",
+            "new_password": "a-much-better-password",
+            "confirm_password": "a-much-better-password",
+        },
+        follow_redirects=False,
+    )
+    assert "error=" in response.headers["location"]
+
+    user = db.scalar(select(User).where(User.email == registered["email"]))
+    db.refresh(user)
+    from lembas.security.passwords import verify_password
+
+    assert verify_password(registered["password"], user.password_hash)
+
+
+def test_mismatched_confirmation_is_refused(client: TestClient, db, registered):
+    response = client.post(
+        "/api/preferences/password",
+        data={
+            "current_password": registered["password"],
+            "new_password": "a-much-better-password",
+            "confirm_password": "a-different-password",
+        },
+        follow_redirects=False,
+    )
+    assert "do%20not%20match" in response.headers["location"]
+
+
+def test_short_new_password_is_refused(client: TestClient, db, registered):
+    response = client.post(
+        "/api/preferences/password",
+        data={
+            "current_password": registered["password"],
+            "new_password": "short",
+            "confirm_password": "short",
+        },
+        follow_redirects=False,
+    )
+    assert "8%20characters" in response.headers["location"]
+
+
+def test_other_sessions_are_revoked_but_this_one_survives(client: TestClient, db, registered):
+    """If the reason for changing a password is that someone else knows it,
+    leaving their session alive defeats the point."""
+    other = TestClient(client.app)
+    other.post(
+        "/auth/login",
+        data={"email": registered["email"], "password": registered["password"]},
+        follow_redirects=False,
+    )
+    assert other.get("/chat", follow_redirects=False).status_code == 200
+    assert db.scalar(select(SessionRow)) is not None
+
+    client.post(
+        "/api/preferences/password",
+        data={
+            "current_password": registered["password"],
+            "new_password": "a-much-better-password",
+            "confirm_password": "a-much-better-password",
+        },
+        follow_redirects=False,
+    )
+
+    # The other browser is out...
+    assert other.get("/chat", follow_redirects=False).status_code == 303
+    # ...and the tab that made the change is still in.
+    assert client.get("/chat", follow_redirects=False).status_code == 200