# What we do not do

> The architecture explained by its omissions: no JavaScript dialog, no listener per instance, no MutationObserver, no mirrored state, no Provider, no positioning engine, no forced virtualization, no hidden cost.

Page: https://svelte-lean.vercel.app/docs/what-we-dont-do · Markdown: https://svelte-lean.vercel.app/docs/what-we-dont-do.md · Index: https://svelte-lean.vercel.app/llms.txt

Each omission below is a rule of the repository's architecture contract, with its reason and where it is enforced.

## Omissions

| We do not | Because | Enforced by |
| --- | --- | --- |
| Build a JavaScript dialog | `<dialog>` provides the top layer, inertness, Escape, focus return and the backdrop. | Dialog contract; native-only fixture, Svelte Lean chunk 0 B |
| Add a listener per instance | One listener per event type routes along `composedPath()` for every root. | Forbidden changes, tabs.test.ts, listeners.spec.ts (1 and 1000 roots, counted two ways) |
| Discover roots with a `MutationObserver` | The router finds a root on its first event; an observer adds work on every update. | ADR 0004; the audit's `grep -rn MutationObserver packages/*/src` returns nothing |
| Mirror native state into Svelte state | `open`, `checked`, `disabled` and focus are in the DOM; a copy can drift. | Tabs unit test asserts no `WeakMap` in the behavior |
| Require a Provider | Theme is CSS tokens; the runtime attaches to the document. | `grep -rni provider packages/*/src` returns nothing |
| Ship a positioning engine | CSS anchor positioning places popovers; without it the platform default placement is the documented fallback. | `grep -rni floating-ui packages/*/src` returns nothing |
| Force virtualization or a component per cell | `<DataTable />` renders a native `<table>`; grouping, pivot, clipboard, export, server data and persistence load only when imported. | table-basic fixture |
| Hide runtime cost | Every primitive page shows its tier, listeners and bytes (tabs: 1839 B brotli). | Measurement files; the [proof page](https://svelte-lean.vercel.app/proof.md) reads live listeners |

The table's state object is application state by design, not a mirror. Virtual rows are not shipped.

## Also not

- Random ids for ARIA relationships.
- `document` or `window` access at module evaluation.
- `eval`, `new Function` or string-to-code attributes (strict CSP safe).
- A Tailwind or CSS-in-JS dependency.
- A production dependency without a written reason.
- A root entry that registers every behavior.
- A rename of a protocol attribute, event, token or export without a deprecation window.

Full list: "Forbidden changes" in AGENTS.md. Costs: [Trade-offs](https://svelte-lean.vercel.app/docs/trade-offs.md).