Canvas pane

The Canvas is a second pane that opens to the right of the chat thread. It appears when the reply contains content the linear thread cannot hold well — a long code block, a Mermaid diagram, a structured document, a runnable Python script. Inline replies stay short and readable; everything else moves out of the way.

The Canvas is not a separate document area or a richer composer. It is a render destination — the agent decides what goes there based on the shape of its output, and the user sees it without having to ask.

What the Canvas is

The Canvas opens automatically the first time a reply produces Canvas-worthy content. The thread keeps a short pointer ("Source", "Preview") at the spot in the conversation where the Canvas content was generated; the right-hand pane holds the actual content. Toggle between Source and Preview at the top of the Canvas to read raw code or see the rendered result; Download saves the current Canvas content to a file.

When it auto-opens

The Canvas opens for several render kinds the inline thread would crowd: Code (any language), HTML, Mermaid diagrams, SVG, long Markdown documents the agent produced, and runnable scripts — Python (sandbox), Node (sandbox), Script (sandbox). Run-code outputs land in the Canvas alongside the script so a single pane shows code and result. Short snippets the inline thread can hold do not trigger the Canvas — the threshold is rough but consistent across kinds.

Editing in the Canvas

The Canvas is a render surface for whatever the agent produced. Editing the rendered content means asking the agent to revise it — a follow-up message in the thread ("change the timeout to 30 seconds", "make the diagram horizontal") triggers a new generation that replaces the Canvas content. There is no direct-edit mode; the agent owns what is in the Canvas.

Persistence across the chat

The Canvas content is part of the chat, not a separate file. Reopening the chat later reopens the Canvas with the latest content; switching to another chat closes the Canvas pane until that chat produces or carries Canvas content of its own. Sharing the chat with Share chat carries the Canvas across — the viewer sees the same Source / Preview toggle, in read-only mode.

Where this fits

The Canvas is the answer to "what happens when the reply is too big for the thread". It composes with everything else in Chat — agents, attachments, voice, shared chats — without those features needing to know about it. The next read that sometimes matters: Build a custom tool walks an agent that produces runnable Python in the Canvas, end to end, on a fresh instance.