A terminal panel beside an agent chat

A real shell on the chat's own connection, opened and closed like the
inspector and never beside it. The modes govern the model; what a person
types is theirs, since they hold the credential and could open the same
shell with an ssh client. The model cannot see the panel -- a button
copies the output you choose into the composer.

The session outlives the socket: closing the panel leaves a build
running, and coming back reattaches with the scrollback. Two tabs share
one shell and the smaller window decides the size. It ends on an idle
timeout, on deleting the chat, on disabling, moving or deleting the
connection, and on a restart -- which says why rather than quietly
opening a fresh shell that has lost the working directory.

The nginx template's `Connection ""` is right for SSE and fails every
WebSocket handshake, so `location /` now uses a `map $http_upgrade`;
update.sh grows a drift check for it, because the only symptom on a
stale vhost is a panel that cannot connect.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

deploy/README.md

@@ -81,6 +81,29 @@ 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
@@ -97,3 +120,14 @@ 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.