Intel / article

Release: datasette-apps 0.2a0

Source: simonwillison.net
Author: Simon Willison
Date: Published Aug 1, 2026

Why it matters

Shows a working pattern for letting an safely test UI changes it just made — running JS against a hidden, non-interactive iframe instance of the app — without disrupting what the user sees, useful for anyone building agent-driven app editors.

Terms in this piece · Glossary

AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
context window — The maximum amount of text a model can consider at once — its working memory for the current conversation or task.

Key quotes

“The app_debug() tool is pretty neat: it works by displaying the app in a opacity: 0 iframe with pointer-events: none (so it can't be seen or interacted with) and then executing agent-provided JavaScript inside that sandboxed iframe.”

“This means the agent can smoke test that the app is working and even do things like measure the dimensions of different elements.”

Read the source simonwillison.net