# Context: the verification contract

`scripts/verify.mjs` is 13 KB, 42 `throw new Error` sites, 16 checkpoints. It
reads 26 source files and asserts that specific **string tokens** appear in them
— `data-phase="plan"`, `renderTree`, `.change-lens`,
`styles.css?v=20260904-vote-widget`, and so on.

## Why this matters more than it looks

These assertions are the only thing standing between this site and silent
content loss during a large refactor. They are also **all going to break**,
because they assert against files that will stop existing.

The failure mode to guard against: an agent runs `pnpm run verify`, sees red,
and "fixes" it by deleting the assertion. The suite goes green and the site
loses a section. **Deleting an assertion is a change that requires review, the
same as deleting a feature.**

## How the contract must evolve

Three kinds of assertion, three different fates:

| Kind                      | Example                                          | Fate                                                                                                                    |
| ------------------------- | ------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------- |
| **Content presence**      | `'data-phase="plan"'` in `full-guide/index.html` | Re-point at built output (`dist/`) — the token should survive rendering. If it does not, the component dropped content. |
| **Implementation detail** | `'const phases'`, `'renderTree'` in `app.js`     | Obsolete. Replace with an assertion about _behaviour or output_, never delete outright.                                 |
| **Cache-busting version** | `'app.js?v=20260904-vote-widget'`                | Obsolete — Astro hashes assets. Replace with "the built HTML references a hashed asset".                                |

**Rule: the assertion count must not fall.** Every removed token is replaced by
one that pins the same user-visible fact against the new architecture. The
verification engineer owns this and is the only role allowed to reduce coverage,
with a written reason per removal.

## The stronger check to add

Token-matching is brittle. During the migration, add a **rendered-output diff**:
snapshot the current site's DOM text content per route, then assert the Astro
build produces the same text. That catches dropped paragraphs the way token
matching cannot.

```bash
# before migrating a page, from the vanilla site:
node .agents/scripts/snapshot-route.mjs /models/ > .agents/snapshots/models.txt
# after: same script against dist/, diff must be empty (or reviewed)
```

See [`../skills/verify-contract/SKILL.md`](../skills/verify-contract/SKILL.md).

## Also in the suite

`scripts/audit-ui.mjs` asserts every page has a viewport meta and **no external
`<script>`/`<link>`**. Keep it and extend it: it currently misses external URLs
inside CSS (`@font-face src`, `@import`, `url()`), which is exactly how the
broken Google Fonts request in `styles.css:1` got in.
