Open a workspace New tab, choose Canvas, then select an HTML, SVG or Markdown file from the thread's checkout. Use the workspace's Full view button to expand it; Escape returns to the conversation. Reload Canvas restarts the preview manually.
Canvas runs local HTML scripts and loads relative styles, scripts, images and fonts. It refreshes the document when its source or a loaded local asset changes, including assets that appear after the document. Polling runs while Canvas is visible. Switching workspace tabs preserves the preview; closing Canvas or its thread releases its guest. Deleted files show an error and recover when restored.
Streamer Mode covers only the Canvas preview while the rest of the workspace stays usable. Turning it off restores the same running preview and selection. Recognized secrets in filename labels are masked without changing the selected path or the file Canvas opens.
Markdown supports headings, paragraphs, lists, fenced code, inline code, bold and web link text. Raw HTML in Markdown is displayed as text. SVG renders as an SVG document. Canvas is a preview, so interactions do not save edits back to the source file.
Each preview runs in its own temporary browser session without Node, a preload, Modex's bridge, permissions, downloads or app credentials. Main serves only supported regular files inside the checkout; symlinks cannot grant access outside it. Hidden paths and unsupported file types are refused. Each resource is limited to 1 MB and a preview can track up to 128 resources. Remote requests, external navigation, frames, form submissions and privileged URLs are blocked. For a development server or a page requiring network access, use the existing workspace browser tab.
Canvas currently requires the full desktop app. The Store client and browser development bridge report it unavailable rather than forwarding preview operations to a host.