tegwick
44faf3de8e
Two decisions taken with the operator: stdlib HTML driver instead of Playwright (F-0004), and a deterministic discovery runtime instead of a live model. Both sit behind interfaces so the alternatives drop in later. - html.py: stdlib DOM parse and query - agentic.py: DiscoveryRuntime (agentic arm, ignores data-td by construction) and RecordedSelectorRuntime (control arm, uses the strongest identifier the page offers) - browser.py: per-actor sessions over real HTTP, constructed per call so no actor inherits another's connection state - cost/nondeterminism metrics recorded from the first run F-0005 (CONCEPT_DRIFT): the H-001 result is a narrowing. Where test ids are preserved, discovery 9/9 and recorded selectors 9/9 - the semantic action buys nothing. Where they are dropped, discovery 2/3 and recorded 0/3. The concept model presents semantic actions as generally superior; the evidence says conditionally superior. M21 and M22 added mid-task: the deciding side of the axis was N=1. M22 (field names renamed) defeats the heuristic and is the first concrete evidence that a live model would add capability, not just cost. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Assistant: claude-code Assistant-Model: opus Assistant-Process: 1629012@bnt-lap001 Assistant-Session: 78d4fb13-8a1e-474b-87a3-9b9261c49a39
60 lines
2.4 KiB
Markdown
60 lines
2.4 KiB
Markdown
---
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id: F-0004
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type: framework-finding
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class: FRAMEWORK_LIMITATION
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status: open
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discovered: "2026-08-22"
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discovered_by: TD-WP-0002-T07
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workplan: TD-WP-0002
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task: TD-WP-0002-T07
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carried_to: TD-WP-0002-T10
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---
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# F-0004 — The browser surface is driven without a browser
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## Decision
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`TD-WP-0002-T07` names Playwright as the browser driver. It was not used.
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Instead, `src/testdriver/html.py` parses the lab's server-rendered HTML with
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`html.parser`, and `src/testdriver/browser.py` drives it over real HTTP.
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Reasons, in order of weight:
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1. **The lab's surface has no JavaScript.** It is server-rendered forms. A
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browser engine would not change what H-001 or H-002 can be measured against —
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the mutations that matter are DOM restructuring, rewording and field renaming,
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all of which a parser faces in full.
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2. **Establishing Playwright is a real cost to the operator** — installation plus
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a licence review, and the usual snag is the Chromium binaries the installer
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pulls rather than the library licence itself. Blocking the vertical spike on
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that was not worth it for a surface that gains nothing from it.
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3. **The stack is deliberately boring.** Zero dependencies remains true.
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`Driver` is a Protocol, so a Playwright implementation sits alongside this one
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without touching the kernel, the oracles or the evidence format.
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## What this costs — stated, not buried
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The driver cannot:
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- execute JavaScript, so **no single-page-application surface can be driven**;
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- take screenshots, so that evidence type listed in `INTENT.md` is unavailable;
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- read an accessibility tree, or observe visual layout at all.
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The third is the most consequential for the thesis. A real mechanical change
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often moves a control *visually* while leaving the DOM largely intact, and this
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driver is blind to that entire class. H-001's mutation set is therefore narrower
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than the hypothesis's wording implies: it tests **structural** durability, not
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**visual** durability.
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That should be said plainly whenever the H-001 result is quoted.
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## Carried to T10
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Two questions, neither answerable now:
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1. Does a Playwright driver actually change the H-001 result, or merely widen the
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surface it can reach? Worth one experiment, not a rewrite.
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2. Is the screenshot evidence type in `INTENT.md` load-bearing, or was it listed
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because screenshots are conventional in this space? If nothing has needed one
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by T10, that is a candidate for compression.
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