Troubleshooting

Match the symptom to the row before changing anything. Several of these look like a broken build and throw nothing. Container and stacking detail: Embedding.

Symptom	Cause	What to do
Chrome renders, clicks / drags / keystrokes do nothing	A second Vue reactivity instance. @templatical/core (or any other Vue-using @templatical/* package) is in the app's own dependencies, so refs the editor creates are invisible to that second WeakMap.	Keep those packages out of the app's dependencies. The editor already bundles them.
Editor mounts, layout is gone	@templatical/editor/style.css was not imported. The exports map resolves that subpath to dist/style.css.	Import the stylesheet next to init(). Do not install tailwindcss as a peer — it is compiled into that file.
Dialogs clipped, painted under host chrome, or a drag ghost that drifts	An ancestor of the container is a containing block for position: fixed: transform, filter, backdrop-filter, perspective, will-change, contain, isolation, opacity below 1, or a positioned element with z-index.	Remove that property from ancestors, or mount outside that stacking context.
Sidebar last items / footer clip, no scroll	The container has no definite height. The editor fills its parent; without one it uses a small anti-collapse floor and chrome still assumes real height.	Give the container a real height (100% of a sized parent, or a px/vh value).
React 18 StrictMode: extra editors, leaked listeners	init() is async. StrictMode unmounts the effect before the promise resolves, so the created instance is never stored and never unmount()ed.	Unmount the instance that just finished when the effect was cancelled. See Installation.
toHtml() throws / toMjml() asks for a package	The SDK ships no MJML compiler. toMjml() lazy-imports @templatical/renderer. HTML is any MJML library, render.compileMjml, or template-tools render --format html.	Install the renderer peer for MJML. Compile HTML on the server. How Rendering Works.
require('@templatical/editor') fails	ESM only. No main, no CJS, no UMD.	Use import. A CJS-only app needs a bundler that can consume ESM.
Theming tokens vanish after all: initial on the container	Inheritance crosses the shadow boundary. Resetting the container wipes --tpl-user-*, which is the theming surface, and can break the height chain.	Do not reset the container. The editor already neutralizes host typography at its own root.

The Agent Skill's diagnose mode walks the same table against an existing init() call.