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Preview renders HTML files (sandboxed, scripts off, local images inlined) #2141
Description
Important
Problem — Preview opens .html files as source text, so an agent-written status page cannot be read in the studio.
Approach — Render .html/.htm in Preview inside a scripts-off, same-origin sandboxed frame. The host prepares the document first: strips scripts, meta refresh, base and embedded frames; inlines locally referenced images as data URIs; then intercepts link clicks. A Rendered/Source toggle mirrors Markdown's, and the existing zoom controls apply.
Scope — in: rendering, preparation, image inlining, link routing, toggle, zoom, scroll kept across re-renders · out: live-refresh extensions (sub-issue 2), pop-out (sub-issue 3), page scripts.
Acceptance Criteria
- An
.htmlor.htmfile opens rendered by default; the toggle switches to the source editor and back; saving from Source re-renders. - Scripts, inline event handlers and meta refresh in the page have no effect (the prepared document contains no script, meta refresh, base, iframe, object or embed elements).
- Relative, absolute-path and
file://image sources are resolved against the page's folder and inlined;httpsand data sources are left alone; inlining stops at a fixed count and size budget. -
httpslink clicks open the system browser; relative andfile://link clicks open the target in Preview for the same session; in-page#anchorlinks scroll; nothing navigates the frame. - Zoom in/out/reset changes the page scale; re-rendering the same file keeps the scroll position.
Testing Decisions
Pure preparation and link classification live in their own module with unit tests (happy-dom: script/refresh stripping, image path resolution, budget, link classes). Extend the Preview routing test for the new category.
Key Decisions
The sandbox allows same-origin and never scripts. Image bytes come through the engine's file read, which already serves image/PDF bytes to Preview.
Source
Part of #2140.
Activity