Previews
Your agent builds the prototype. Radial gives it a URL.
Coding agents mock up ideas in single-file HTML. Attach one to an issue and everyone in the workspace gets it rendered at a Radial URL, with comments on the file itself. No deploy, no hosting, no screenshot decaying in a Slack thread.
$ radial attach RAD-42 billing-v2.html ✓ Attached billing-v2.html to RAD-42 Preview: https://app.radial.build/p/acme/RAD-42/f3a9c1
The prototype your agent already built during planning, reviewed where the work is tracked. That URL is the whole product: click it, and you are inside a Radial frame with every prototype on the issue in one menu.
One command to review
radial attach RAD-42 prototype.html prints a Preview URL. Same capability over MCP and REST, so your agent can attach mid-plan without a human touching a browser.
Reviewed where the work is tracked
The URL is workspace-only and wrapped in Radial. Every HTML file on the issue sits in the Preview menu, comments are scoped per file, and the decision lands on the issue timeline your agent reads next.
Sandboxed on purpose
Every prototype renders as untrusted code: an opaque, sandboxed frame with no reach into your Radial session, cookies, or data. We assume the worst about the file so you can look at it without thinking about it.
How we render untrusted HTML
We treat every prototype as hostile code.
A prototype is bytes someone (or some agent) uploaded. So Radial serves it under a content-security sandbox on an opaque origin: it cannot read your cookies, reach your session, touch the Radial page around it, or navigate your tab somewhere else. It runs in a box with the door welded shut, and it does so even if you open the raw file directly. Only the workspace can see it, and only rendered HTML renders — everything else downloads.
You’re rendering arbitrary HTML?
Yes, and that is the feature. Prototypes are untrusted code by default here: they render in a sandbox on an opaque origin with no access to your session or data. Most teams reviewing agent HTML today double-click the file locally with zero isolation. The Preview is the safer path, not the riskier one.
Why not just deploy it to Vercel or Netlify?
You can, for the thing you’re shipping. A prototype is a question, not a release. Previews skip the repo, the pipeline, and the hosting account; access is workspace membership, not a URL you hope stays obscure; and the feedback lands on the issue instead of a deploy nobody can find in three weeks.
Attach a prototype. Get a Preview.