inline-embeds

Development

How to render interactive previews of app screens inline in agent chat via sandboxed iframes. Covers the `embed` fence syntax, the `postNavigate` pop-out helper, and when to prefer an embed over prose / a static image.

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Source SKILL.md: https://github.com/BuilderIO/agent-native/blob/HEAD/packages/core/src/templates/default/.agents/skills/inline-embeds/SKILL.md

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Inline Embeds

The chat renderer lets you embed a sandboxed iframe pointing at any same-origin route of this app, rendered inline with your reply. Use this when a live, interactive preview communicates more than prose or a static screenshot — a chart, an email thread, a slide, a form, a ticket.

The `embed` fence

Emit a fenced code block with the language embed:

```embed
src: /email?id=msg_123
aspect: 4/3
title: Re: Q4 planning
```

Keys:

Key	Required	Notes
`src`	yes	Same-origin path beginning with `/`. Cross-origin URLs are blocked
`aspect`	no	`16/9` (default), `4/3`, `3/2`, `2/1`, `21/9`, `1/1`
`title`	no	Accessible label + hover tooltip
`height`	no	Fixed pixel height when aspect ratio doesn't fit

The rendered iframe is sandboxed (allow-scripts allow-same-origin allow-forms allow-popups) and referrerpolicy="same-origin". The browser enforces that the iframe can't navigate the parent window.

When to reach for an embed

A chart or visualization that benefits from tooltips / hover.
A detail view the user might want to scan (email, ticket, event, slide).
Anything where "here's a link to it" would force an extra click.

Don't embed when plain prose, a bulleted list, or a small table is enough. Don't embed external sites — the renderer blocks cross-origin URLs.

"Open in main window" button — `postNavigate`

Every embed route should include a small "Open" button so the user can pop the view out of the chat and into the full app. Import the helper from @agent-native/core/client:

import { postNavigate, isInAgentEmbed } from "@agent-native/core/client";

export function OpenButton({ path }: { path: string }) {
  if (!isInAgentEmbed()) return null;
  return (
    <button onClick={() => postNavigate(path)}>Open</button>
  );
}

postNavigate sends a postMessage to the parent chat window. The chat renderer validates the message is same-origin, same-iframe, and the path is relative, then updates the parent URL via history.pushState so react-router navigates without a page reload.

When the page is loaded directly (not in an iframe), postNavigate falls back to a same-window navigation, so the button works both ways.

Adding an embed route to a template

Create a chromeless route (e.g. app/routes/email.tsx) that renders the detail view without the app shell.
Mark the route path as bare in app/components/layout/Layout.tsx so the sidebar / header don't render inside the iframe.
Render the existing detail component with a transparent background so it blends into the chat theme.
Include an <OpenButton> that calls postNavigate("/path/to/detail").
Document the embed URL in this template's AGENTS.md so the agent knows what's embeddable.

The framework-level fence renderer and security enforcement apply automatically — no per-template wiring beyond the route and layout bypass.