---
id: F-0005
type: framework-finding
class: CONCEPT_DRIFT
status: open
discovered: "2026-08-22"
discovered_by: TD-WP-0002-T07
workplan: TD-WP-0002
task: TD-WP-0002-T07
hypotheses: [H-001]
carried_to: TD-WP-0002-T10
---

# F-0005 — Semantic actions earn their keep more narrowly than claimed

## The claim as written

H-001, from `TestDriverImprovementLoop.md` § 3:

> A semantic action survives implementation restructuring better than a recorded
> UI interaction sequence.

`INTENT.md` treats this as foundational — semantic actions are "the bridge
between agentic exploration and deterministic crystallization".

## The measurement

Twelve mechanical mutations, two arms, same semantic action
(`grant_access(Bob, R, READ)`), same surface, same oracles.

| | Discovery (agentic) | Recorded selectors (control) |
|---|---|---|
| test ids **preserved** (9 mutations) | 9/9 | **9/9** |
| test ids **dropped** (3 mutations) | 2/3 | 0/3 |

The control arm is not a straw man: it uses stable `data-td` attributes, which is
what a well-instrumented application provides and what good practice recommends.
`test_the_control_arm_is_not_a_straw_man` asserts it keeps winning where those
attributes survive.

## What this actually says

**Where an application is well instrumented and keeps its identifiers, the
semantic action buys nothing.** Nine mutations, two arms, identical results. The
conventional approach is not merely adequate there — it is cheaper, faster and
deterministic.

The semantic action earns its keep in exactly one circumstance: **when stable
identifiers are absent or are not carried forward through a change.** That is a
real and common circumstance — a rewrite rarely preserves test ids, and a large
share of applications never had them — but it is much narrower than "survives
implementation restructuring better", which reads as a general claim.

## The second boundary: M22

Discovery fails on M22, where form field names change (`subject_id` →
`recipient`) with test ids dropped. The heuristic runtime scores candidates
partly on field names, so renaming them removes a signal it depends on.

This is an honest limit rather than a bug. It marks where a scripted runtime
stops and where a model plausibly starts: the page still carries the label
"Person" next to the field, which a model could read and a keyword heuristic
cannot. **M22 is the first concrete piece of evidence that a live model would add
capability rather than merely cost** — worth more than a general argument that it
might.

## Consequences

1. **H-001 must never be quoted as a single rate.** Split by the test-id axis or
   it is misleading. `research/hypotheses/H-001-semantic-action-stability.md` now
   records the split.
2. **The concept model overstates this.** `INTENT.md` and the Concept Model
   present semantic actions as generally superior. The evidence says
   conditionally superior. Classified `CONCEPT_DRIFT` — the concept should be
   revised to match the evidence (§ 5 path 2), not the other way round.
3. **Three mutations is still thin.** 2/3 and 0/3 are directionally clear and
   statistically nothing. Any stronger statement needs more mutations on the
   dropped-identifier side. Recorded rather than rounded up.
4. See also **F-0004**: this driver tests structural durability only. Visual
   relayout, the other major mechanical change class, is untested entirely.