# Changelog

> True HMR for Lit components, CSS delivery helpers, and a DevTools timeline for Vite.

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## Version 0.4.0

Sep 29, 2026

A maintenance release. The timeline panel stays fast with a full buffer, the live inspector stops walking the whole page, and several failures that used to pass silently now say so. Releases are published from CI now.

### Added

* **Verbose render layer.** lit-html’s per-part debug events (template instantiation, `set part`, each binding commit) go to a new “Lit Render (verbose)” layer. It is off by default, because it fires once per binding on every render. Values are summarized as strings (`string:"…"`, `node:<li>`, `template`, `function:onClick`) and never passed through.
* **Releases from a version tag.** Pushing a `v*` tag runs the CI gate, checks the tag against `package.json` and `CHANGELOG.md`, publishes to npm over trusted publishing (OIDC), and creates the GitHub Release from the changelog section. Prereleases go to the `next` dist-tag.

### Changed

* **The timeline list renders only the visible rows**, through `@lit-labs/virtualizer`. A 2500-event recording keeps about 75 rows in the DOM instead of one per event. Filtering reruns only when the events or filters change.
* **Live inspector mode no longer re-walks the page on every mutation.** Batches with no custom element or shadow root in them are dropped, and relevant batches walk only the subtrees they added.
* **The docs site was rewritten** in plain language, with a tutorial, task-sized DevTools guides, a troubleshooting page, screenshots in both themes, and the Lit Design System’s colours and type.

### Fixed

* The source overlay’s default hotkey is Ctrl+Shift+S, as documented. The runtime used to fall back to `e`, which also collided with the DevTools pick command.
* The source overlay removes its HMR listeners when it disconnects. Moving the element used to register the toggle twice, so the Vite DevTools overlay command did nothing, and a removed overlay kept reacting.
* `urlSheet()` and `?css-sheet` warn when a stylesheet fails to load, and treat non-ok responses as failures. A 404 used to hand Vite’s fallback page to the sheet as CSS, with a clean console. The sheet keeps its last good CSS.
* An unknown `LIT_PLUGIN_HMR_ON_INCOMPATIBLE` value logs a warning and falls back to the default, instead of quietly acting as `reload`.
* The Lightning CSS pass over `css` literals finds them by parsing the module, so `css`-tagged text inside a string, a comment, or another template literal is no longer rewritten.