T07: agentic realization over a stdlib browser surface

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

research/concepts/fitness-map.md

@@ -1,6 +1,6 @@
 # Concept ↔ Implementation Fitness Map
 
-**Updated:** 2026-08-22 (TD-WP-0002-T06)
+**Updated:** 2026-08-22 (TD-WP-0002-T07)
 
 Traces each important concept to the implementation, experiment and evidence that
 support it. **Unsupported entries are the point of this map** — a concept with no
@@ -13,8 +13,12 @@ Support levels follow `TestDriverImprovementLoop.md` §13:
 
 ## Current state
 
+`C-semantic-action` is the first concept to reach `C2`: it has an experiment
+behind it (the T07 two-arm comparison), and that experiment narrowed the claim
+rather than confirming it. Everything else still rests on unit tests.
+
 The deterministic kernel exists (T04) and its guarantees are covered by unit
-tests. **Levels have not moved.** A passing unit test is not an experiment: it
+tests. **Levels do not move for those.** A passing unit test is not an experiment: it
 shows the code does what its author intended, not that the concept holds under
 the mutations it claims to survive. Levels rise when E-001/E-002/E-003 produce
 evidence, not before. The implementation column below moves; the level column
@@ -26,7 +30,7 @@ were aspirational, not evidenced.
 |---|---|---|---|---|---|
 | `C-use-case` | C1 | `intent.py` | — | — | Is a use case expressible without leaking mechanics? |
 | `C-actor-isolation` | C1 | `world.py` | E-001 | `td://self/actor-isolation` | **F-0003** — only observable when the scenario plants canaries. |
-| `C-semantic-action` | C1 | `actions.py` | E-001 | — | Does identity survive restructuring better than a recorded sequence? (H-001) |
+| `C-semantic-action` | **C2** | `actions.py`, `agentic.py` | E-001 (partial) | T07 arm comparison | **F-0005** — supported only where stable identifiers are absent. Narrower than the concept model claims. |
 | `C-oracle-independence` | C1 | `runner.py`, `oracles.py` | E-001, E-003 | — | Independence of components ≠ independence of belief. (H-004) |
 | `C-evidence-pack` | C1 | `evidence.py` | — | `td://self/evidence-reproducibility` | Verdicts are reproducible from S3 alone, on passing and failing runs. |
 | `C-observation-channel` | C1 | `lab/app.py` | — | — | **D-07** — required of every system under test. Adoption cost unknown. |

research/findings/F-0004-stdlib-driver-instead-of-playwright.md

@@ -0,0 +1,60 @@
+---
+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.

research/findings/F-0005-semantic-actions-earn-their-keep-narrowly.md

@@ -0,0 +1,80 @@
+---
+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.

research/hypotheses/H-001-semantic-action-stability.md

@@ -1,7 +1,7 @@
 ---
 id: H-001
 title: Semantic Action Stability
-status: PROPOSED
+status: EXPERIMENTING
 created: "2026-08-22"
 experiments: [E-001]
 concepts: [C-semantic-action]
@@ -36,6 +36,28 @@ The comparison is unfair if arm B is built naively — a brittle straw man makes
 H-001 trivially true and worthless. Arm B uses the most robust selector strategy
 reasonably available (roles, labels, test ids where the lab provides them).
 
+## Result so far (TD-WP-0002-T07)
+
+Twelve mechanical mutations, both arms, same semantic action:
+
+| | Discovery (agentic) | Recorded selectors (control) |
+|---|---|---|
+| test ids preserved (9) | 9/9 | **9/9** |
+| test ids dropped (3) | 2/3 | 0/3 |
+
+**Not falsified, but substantially narrowed.** Where stable identifiers survive,
+the control arm matches the agentic arm exactly — the semantic action buys
+nothing. It earns its keep only where identifiers are absent or not carried
+forward.
+
+Three mutations on the deciding side is directionally clear and statistically
+nothing. See `research/findings/F-0005-...` — the concept model overstates this
+and should be revised to match the evidence.
+
+Scope caveat (F-0004): the driver tests **structural** durability only. Visual
+relayout is untested.
+
 ## Status log
 
 - 2026-08-22 `PROPOSED`. No evidence.
+- 2026-08-22 `EXPERIMENTING`. Partial evidence from T07; awaiting E-001 in full.

research/hypotheses/H-002-mechanical-adaptation.md

@@ -1,7 +1,7 @@
 ---
 id: H-002
 title: Mechanical Adaptation
-status: PROPOSED
+status: EXPERIMENTING
 created: "2026-08-22"
 experiments: [E-001]
 concepts: [C-adaptation]
@@ -33,8 +33,20 @@ at all.
   (`docs/TestDriverClassificationDesign.md` D-02). Any non-empty diff is both a
   falsification signal **and** a framework defect, since no write path should exist.
 
+## Result so far (TD-WP-0002-T07)
+
+Discovery recovered from 11 of 12 mechanical mutations with **no claim or
+invariant diff in any run**, as D-02 requires structurally. The single failure
+(M22, field names renamed) failed *loudly* — a `RealizationFailed` recorded in
+evidence, not a silent pass. That distinction is the one that matters: the
+framework reported that it could not act, rather than reporting that nothing was
+wrong.
+
+Full classification of recovery vs defect is T08.
+
 ## Status log
 
-- 2026-08-22 `PROPOSED`. Design decision D-02 makes the second falsification
+- 2026-08-22 `PROPOSED`.
+- 2026-08-22 `EXPERIMENTING`. Recovery demonstrated; classification pending T08. Design decision D-02 makes the second falsification
   branch structurally unreachable; the measurement is retained anyway, as an
   assertion that the architecture is what we believe it is.