The preview went through a proxy written into this plugin. The platform already had one —
/api/dev-proxy/:port/* — and it is better in exactly the ways the copy was worst.
Authentication. An iframe navigation cannot carry an Authorization header, and the copy answered that
by putting a token on the URL and on every asset the page then requested. The platform's answer is a
short-lived cookie obtained by an ordinary authenticated request, and its own comments say why: a
token on an iframe URL is a guess about which key the browser stored it under. It had been tried
there and rejected before this plugin repeated it.
Coverage. The copy rewrote URLs with a regex over the markup, which catches only what is written into
the document. The platform injects a script that patches fetch, XMLHttpRequest and WebSocket, so URLs
the page BUILDS at runtime are moved as well — which is most of them in a modern dev server. It also
normalises `..`, forwards HMR, and has nineteen tests behind it.
So the plugin's proxy is gone, previewUrl with it, and the panel does what the platform's Preview
panel does: ask for the session, then mount the frame at the dev port.
No sandbox attribute, for the reason that panel gives. Without allow-same-origin a frame has an opaque
origin and no storage; with allow-same-origin and allow-scripts it can reach up and remove its own
sandbox attribute. Claiming a protection that does not hold is worse than not claiming it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
pastilhasandClaude Opus 5
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