# U3 landed — the page declares the seam, the Booth mounts into it

_2026-09-22 · booth_

**Ten regular expressions against author-written HTML are gone.** Six in
`wrap_verbatim_html` hunting for somewhere to hang a favicon and a chip, four in
`booth/inline.py` substituting rendered ask markup into the author's own tags.
What replaced them, in full:

```python
return html if declares_embed(html) else html + EMBED_SCRIPT_TAG
```

A substring test and a `+`. **Both of the old wrapper's hard constraints stopped
existing rather than being satisfied more carefully** — nothing can displace a
leading doctype into quirks mode and nothing can push the charset `<meta>` out
of its first-1024-byte window, because nothing in front of them ever moves.

## What moved where

| was | is |
|---|---|
| `wrap_verbatim_html` + 6 regexes | `embed_verbatim` — one `in`, one `+` |
| `booth/inline.py`, 119 lines | deleted; `form_id` survived into `app.py` |
| `_BACK_CHIP`, `asks_chip` | built in the DOM by `embed.js` |
| `inject_asks` | `GET /b/<name>/embed.json` + placement in `embed.js` |
| `_ask_inline.html`'s `styles()` | the CSS lives in `embed.js` |
| `FAVICON_LINK` string injection | `document.querySelector('link[rel~="icon"]')` |

**The fragments are still rendered by Jinja.** `embed.js` places what comes back
and never builds one — a second renderer in JavaScript would be the same bug
INV-1 exists to stop, in a new language. The payload also decides openness
(`open_marks`) and order, so the page has no opinion about either.

## The thing the contract got wrong, and the seam review caught

The payload first keyed `questions` by question key. **A single-question pick
normalizes to `questions: [{"key": None, …}]`** (`asks.normalize_ask`, the
`multi: False` branch), and `json.dumps` writes that key as the string `"null"`
— inventing a name that collides with a real key. Every one-question ask in the
fleet would have hit it, including the live `sindra-voice-1`. `questions` is a
LIST of `{key, html}` now; the key is nullable, and declaration order rides in
the format instead of leaning on object-key insertion order.

The cold contract panel could not have found this: it is a fact about
`booth/asks.py`, which an artifact-only reader never sees. Third time the seam
review has caught what the cold pass structurally cannot — see
[[2026-09-21-two-gates-are-complementary]].

## The live report that was already subtly broken

`dfa-concepts/index.html` writes `<div class="ask" data-booth-ask="dfa:logo">
<h3>The one asset that must survive</h3>`. `_EL_RE` matched the **opening tag**
and replaced it, so the author's `.ask` wrapper class vanished, the heading was
orphaned and the `</div>` went stray. Nobody filed a bug, because a page that is
95% right does not look broken.

`el.insertAdjacentHTML("beforeend", frag)` keeps the element and its contents
and puts the fragment inside. Verified live in a real browser: 5 author `.ask`
wrappers intact, 5 headings intact, 14 radios mounted inside them, zero console
errors. **The replacement is not just less fragile, it renders the operator's
own report more faithfully than the thing it replaced.**

## The cost, stated because it is real

The verbatim path used to work with **no JavaScript** — server-rendered ask, plain
form POST, HTML5 `form=` binding resolved at parse time. It needs the script now.
The operator's 2026-09-21 ruling accepts that; this entry records the consequence
so nobody meets it as a surprise. The never-invisible guarantee survives in a
weaker and still-true form through surfaces needing no script: the index card's
open-mark badge, and `/b/<name>/marks`.

## Anchor syntax

`data-booth-mark` is canonical (U2 made an ask one shape of mark).
`data-booth-ask` is a kept alias — 2 of the 4 live verbatim booths spell it that
way, in the operator's own reports, and the alias is one clause in one selector
string. The `<!-- booth:ask … -->` comment forms were **dropped, not ported**:
zero users across all 21 live booths, and a page that used one falls back to the
append path, so its ask still renders.

## Verification

431 tests (410 → 431). Live: all 21 booths 200, and each of the four verbatim
booths grew by exactly 46 bytes — `len(EMBED_SCRIPT_TAG)`, one append, nothing
else. Related: [[2026-09-22-the-browser-became-a-test-surface]],
[[2026-09-22-seven-of-seven-falsifiers]],
[[2026-09-21-regex-injecting-chrome]].