---
id: F-0004
type: framework-finding
class: FRAMEWORK_LIMITATION
status: open
discovered: "2026-08-22"
discovered_by: TD-WP-0002-T07
workplan: TD-WP-0002
task: TD-WP-0002-T07
carried_to: TD-WP-0002-T10
---

# F-0004 — The browser surface is driven without a browser

## Decision

`TD-WP-0002-T07` names Playwright as the browser driver. It was not used.
Instead, `src/testdriver/html.py` parses the lab's server-rendered HTML with
`html.parser`, and `src/testdriver/browser.py` drives it over real HTTP.

Reasons, in order of weight:

1. **The lab's surface has no JavaScript.** It is server-rendered forms. A
   browser engine would not change what H-001 or H-002 can be measured against —
   the mutations that matter are DOM restructuring, rewording and field renaming,
   all of which a parser faces in full.
2. **Establishing Playwright is a real cost to the operator** — installation plus
   a licence review, and the usual snag is the Chromium binaries the installer
   pulls rather than the library licence itself. Blocking the vertical spike on
   that was not worth it for a surface that gains nothing from it.
3. **The stack is deliberately boring.** Zero dependencies remains true.

`Driver` is a Protocol, so a Playwright implementation sits alongside this one
without touching the kernel, the oracles or the evidence format.

## What this costs — stated, not buried

The driver cannot:

- execute JavaScript, so **no single-page-application surface can be driven**;
- take screenshots, so that evidence type listed in `INTENT.md` is unavailable;
- read an accessibility tree, or observe visual layout at all.

The third is the most consequential for the thesis. A real mechanical change
often moves a control *visually* while leaving the DOM largely intact, and this
driver is blind to that entire class. H-001's mutation set is therefore narrower
than the hypothesis's wording implies: it tests **structural** durability, not
**visual** durability.

That should be said plainly whenever the H-001 result is quoted.

## Carried to T10

Two questions, neither answerable now:

1. Does a Playwright driver actually change the H-001 result, or merely widen the
   surface it can reach? Worth one experiment, not a rewrite.
2. Is the screenshot evidence type in `INTENT.md` load-bearing, or was it listed
   because screenshots are conventional in this space? If nothing has needed one
   by T10, that is a candidate for compression.