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Build Errors and Preview Warnings

The error bar that will not scroll away, and the quality warnings that catch a page that built fine but looks wrong.

The pinned error bar

When a build fails, the errors are pinned in a bar under the chat header — not left in the timeline, where the AI's next answer pushes them out of sight.

It cannot scroll away. It stays there while any error is outstanding, and as each one is fixed it is struck through rather than quietly removed, so a list of three visibly becomes "two left" instead of shrinking behind your back. When they are all gone the bar collapses into a green line you dismiss yourself.

An error that comes back loses its tick again.

What counts as fixed

The preview rebuilds after every edit and reports what it still sees. An error missing from the newest finished report is what marks it fixed.

Half-finished builds change nothing on the bar — a build still running proves neither that an error is gone nor that it is back.

Warnings on a build that succeeded

A page can build perfectly and still be wrong, so after it paints, the preview measures itself and adds plain-language warnings to the Preview built line. They catch the three failures a green build hides:

• styles that never arrive — the page is using class names no stylesheet defines, which is what an unstyled stack of text looks like from the inside;
• broken words in your copy — visible undefined, NaN or [object Object] where a real value was meant to be;
• links that cannot work — a phone link with its scheme doubled, so tapping it does nothing.

The AI does not read these by itself, so typing fix the warnings sends none of them. Press Fix these for me on the card instead: it puts every warning into a message for the AI.

These checks exist because of a real site: it built green, and shipped with an unstyled page, a button reading "Bel undefined" and two dead tap-to-call links. Every file was individually plausible — nothing had ever checked them against each other.

Where to next

• Next in Code Studio (IDE): The Customize Panel
• Errors cleared at last: Publishing a Web App — The security check and putting the app on the internet.
• Starting from scratch here: Web App Studio — The build pill and the diagnosis card in the preview.

8 of 37 in Code Studio (IDE) · Last checked 16 September 2026 · Previous: A Cinematic Website Opening