Look around the machine before deciding to talk about it

The terminal and the canvas both needed a Chat, so they were missing from the
one screen where you are choosing which machine to work on. A draft is the
smallest thing that fixes it: an id, and the three facts behind it.

The trick is that a draft resolves to a *transient* Chat -- constructed, never
added to a session. `canvas.agent_ready`, `_executor`, `_load_agent`, `_save_agent`
and `agent_session.resolve` read exactly four attributes between them and none
of them queries or writes the row, so all of it works unchanged and nothing had
to learn what a draft is. Proven against a real sshd rather than a stub: a
transient chat opens and saves a project file over the same SFTP path a real one
uses, and the database stays empty throughout.

Chats are still created lazily. A draft is not a chat and never becomes one;
when the first prompt makes the real one, the shell is re-keyed into it and the
open tabs are copied across. `terminal.rekey` moves the registry key *and*
`session.chat_id`, because close_for_profile, close_for_owner and the reaper all
pop by the field -- a stale one would leave a dead session that `get` keeps
handing out. The shell is only adopted when its profile and directory match the
chat as finally resolved, since `_new_chat` settles an empty directory to the
connection's own; otherwise it is left alone rather than transplanted onto a
chat that says it runs elsewhere.

Two canvas sources are refused on a draft, by name, and one of them is a hole
rather than an inconvenience. `_load_file` authorises with
`attachment.chat_id != chat.id`, and an upload made on the new-chat screen is
stored with `chat_id=None` -- so a draft whose chat carried no id would make that
comparison `None != None`, which is False, and open every unclaimed attachment
its owner has. `as_chat` does set an id, so it already fails; the refusal is
stated anyway, because a guarantee that lives in an id-shaped coincidence is one
the next change breaks without noticing.

Adoption needed almost no JavaScript: start_chat already answers with
HX-Redirect, so the page reloads and the canvas adopts by construction while the
terminal reconnects to the re-keyed session and replays its scrollback -- the "a
reload is indistinguishable from a second tab" property working for us. What
re-points them mid-screen is a `lembas:agent-target` event, dispatched from
`setDir` and the connection select because assigning to a hidden field's value
fires nothing on its own. Driven under a DOM stub before committing.

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

src/lembas/web/templates/chat/_canvas.html

@@ -16,7 +16,7 @@
 #}
 <aside class="canvas" id="canvas" hidden aria-label="Canvas"
        data-canvas
-       data-chat="{{ chat.id }}"
+       data-chat="{{ chat.id if chat else "" }}"
        data-resize-target>
   {# The left edge, dragged. A separator rather than a decoration: it takes
      focus and answers the arrow keys, or the panel is only resizable with a
@@ -28,7 +28,10 @@
   </div>
 
   <div class="canvas__inner" id="canvas-inner"
-       hx-get="/api/chats/{{ chat.id }}/canvas"
+       {# Before a chat exists this fetches nothing until `draft.js` rewrites it,
+     which is what "intersect once" gives for free: the panel is hidden until
+     it is opened, so the trigger has not fired yet. #}
+       hx-get="{{ "/api/chats/" ~ chat.id ~ "/canvas" if chat else "" }}"
        hx-trigger="intersect once"
        hx-target="this" hx-swap="innerHTML">
     <div class="panel-head">

src/lembas/web/templates/chat/_terminal.html

@@ -12,9 +12,12 @@
 #}
 <aside class="terminal" id="terminal" hidden aria-label="Terminal"
        data-terminal
-       data-url="/api/chats/{{ chat.id }}/terminal/ws"
+       {# Empty before a chat exists: `draft.js` writes a draft id in as soon as
+          the composer has a connection selected. Explicit rather than relying on
+          Jinja rendering `None.id` as nothing. #}
+       data-url="{{ "/api/chats/" ~ chat.id ~ "/terminal/ws" if chat else "" }}"
        data-label="{{ agent_profile.name if agent_profile else 'this connection' }}"
-       data-dir="{{ chat.project_dir }}"
+       data-dir="{{ chat.project_dir if chat else "" }}"
        data-resize-target>
   {#
     The left edge, dragged. A separator rather than a decoration: it takes

src/lembas/web/templates/chat/index.html

@@ -347,6 +347,12 @@
 {# Unconditional: every chat has a transcript, and this is what keeps a block
    somebody opened open across the swaps that arrive twelve times a second. #}
 <script src="{{ url_for('static', path='js/steps.js') }}" defer></script>
+{% if not chat and (canvas_enabled or terminal_enabled) %}
+{# Only where there is no chat yet. It points both panels at a draft id for
+   whatever the composer has selected, and does nothing at all once a chat
+   exists -- which is every other page this block renders on. #}
+<script src="{{ url_for('static', path='js/draft.js') }}" defer></script>
+{% endif %}
 {% if canvas_enabled %}
 <script src="{{ url_for('static', path='js/canvas.js') }}" defer></script>
 {% endif %}