Atrium

Render .html and .md files inline in VS Code instead of opening source.

Clicking a markdown or HTML file in the Explorer renders it as a real page — styled markdown, full HTML documents in a sandboxed iframe with relative URLs resolved. Right-click → Open With → Text Editor when you want to edit.

What it renders

Markdown → styled HTML. Headings, lists, code blocks, tables, task lists, blockquotes, links, images.
Full HTML documents (anything with <!DOCTYPE> or <html>) → sandboxed srcdoc iframe. Relative URLs are rewritten to webview URIs so images, stylesheets, and inline scripts work the way they do in a browser.
HTML fragments (no <html> wrapper) → inline against the file's directory as base.
Both live-reload when the file is saved on disk.

Copilot Chat integration (optional)

Atrium registers a URI handler at vscode://vegadevshop.atrium/open?file=<absolute-path>. Any time Copilot Chat (or anything else that emits vscode:// links) ends a response with a link in that format, clicking opens the file directly in Atrium's renderer — no Explorer hunt, no source tab.

Wire Copilot into this by adding to your .github/copilot-instructions.md:

## File references

Whenever I create or edit an `.html` or `.md` file, end the response with:

[label](vscode://vegadevshop.atrium/open?file=<urlencoded-absolute-path>)

<urlencoded-absolute-path> is the file's absolute path through encodeURIComponent.

Settings

None required. Optional: workbench.editorAssociations if you want different defaults for a specific file type. To edit .md as source instead of preview, add:

"workbench.editorAssociations": {
  "*.md": "default"
}

Why a custom editor?

VS Code's built-in markdown preview is a command (Cmd+Shift+V), not a default editor — you have to invoke it each time, and there's no equivalent for HTML at all. Atrium fills the niche of "click a file, see the render, period," for both formats.

Commands

Command	What it does
`Atrium: Open File in Atrium`	Programmatic — opens an absolute path in the renderer. Used by the URI handler.
`Atrium: Check for Updates`	Polls the Marketplace; offers to install if a newer version exists.

License

MIT