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User guide: Side Canvas, Ask and Agents
Specs: Side Canvas

components/otto-canvas/ is the Agents panel in Otto’s side canvas: a prompt field over the list of otto-agents sessions, in one frosted item of the column that slides in from the right edge. It is an app in architecture.toml, and runs as its own process, an otto-kit app started by the compositor from [[exec_once]] in the shipped config. The compositor owns the column; otto-canvas is a client that places one item in it through the otto-canvas-v1 protocol. It does no agent work itself: it hands each request and each opened session to otto-launcher.

The column, its protocol, height sharing and this panel’s drawing are described in depth on Side canvas; this page is the structural overview.

How it runs

src/main.rs is the whole app, a Sessions value run by otto-kit’s AppRunner.

• One canvas item. On start it creates a CanvasItemSurface, tells the column its natural height (set_content_height), asks for the keyboard on show (set_keyboard_interactivity(on_show); on a compositor without that request, a click gives it the keyboard) and applies the frosted material through the surface style protocol.
• A connection only while shown. On shown it starts a SessionFeed from otto-agents-kit, which connects to the service on its own thread and lists the sessions again whenever the service announces a change. On hidden it drops the feed, so a hidden canvas has no connection, and clears the prompt.
• Height. It grows with its rows up to the share of the column the compositor gives it (max_height, protocol version 5) and scrolls past that with otto-kit’s ScrollView. Without a share it stops at a fixed height.
• Handing off. Opening a row asks the session’s opener first, so a Studio session opens in Studio; otherwise it runs otto-launcher --session <URI>. Enter with text typed runs otto-launcher --ask --send -- <text>, and with nothing typed otto-launcher --ask. The launcher runs in its own process group and is reaped on a thread, and the panel then sends dismiss so the canvas slides away.

The keys (arrows, Tab, Ctrl+N/P and the page keys to walk the rows, the field editing keys) and the row painting come from otto-agents-kit, so the panel behaves like the launcher’s agents mode.

Dependencies

• Workspace: otto-agents-kit (session feed, rows, keys, opener) and otto-kit (the app loop, CanvasItemSurface, text input, scrolling, materials).
• At run time: the compositor’s otto-canvas-v1, a running otto-agents for the list, and otto-launcher on $PATH.

Going deeper

• Side canvas and its spec.
• Agents: the service the panel lists.
• components/otto-canvas/AGENTS.md: running a development build against a dev compositor.