---
id: F-0006
type: framework-finding
class: CONCEPT_DRIFT
status: resolved
discovered: "2026-08-22"
resolved: "2026-08-22"
discovered_by: TD-WP-0002-T08
workplan: TD-WP-0002
task: TD-WP-0002-T08
hypotheses: [H-004]
---

# F-0006 — The classifier cannot infer a semantic change, only escalate

## What the design said

`docs/TestDriverClassificationDesign.md` (T02) specifies a decision table with
four outcomes, one of which is `SEMANTIC_CHANGE`:

> | any | yes | unchanged, but the asset's declared claim set differs from the use
> case | `SEMANTIC_CHANGE` → human |

`TestDriverInitialMilestones.md` M6 states the same four-way path:
`IMPLEMENTATION CHANGE` / `INTENT CHANGE` / `PRODUCT DEFECT` / `AMBIGUOUS`.

Both read as though a classifier could look at a run and determine that intended
behaviour had changed.

## What building it showed

It cannot, and the lab already contained the proof before the classifier existed.

**M12** (revocation deferred by product decision, `SEMANTIC`) and **M19**
(revocation propagates after a delay, `DEFECT`) produce *identical* evidence:
same failing assertion, same step, same snapshot, same audit trail.
`test_deferred_revoke_and_revoke_race_are_behaviourally_identical` has asserted
this since T05.

No quantity of evidence distinguishes them, because the difference is not in the
system. It is in whether someone decided the new behaviour was wanted. A
classifier that emitted `SEMANTIC_CHANGE` from evidence would be guessing, and
guessing in the one direction the project cannot afford: `SEMANTIC_CHANGE`
sounds benign, and "the team must have meant it" is exactly the reasoning that
normalizes a defect.

## Resolution

Path 2 — the concept is deliberately revised.

The classifier's output space is now:

| Outcome | Safe to accept | Meaning |
|---|---|---|
| `UNCHANGED` | yes | no observable difference |
| `MECHANICAL_ADAPTATION` | yes | surface moved, every claim still holds |
| `BEHAVIOUR_CHANGED` | **no** | a claim that held no longer holds |
| `INTENT_CHANGED` | **no** | the recorded claim set itself moved |
| `REALIZATION_FAILED` | **no** | the action could not be performed |
| `AMBIGUOUS` | **no** | the evidence does not support a conclusion |

`BEHAVIOUR_CHANGED` replaces both `PRODUCT_DEFECT` and `SEMANTIC_CHANGE`.
Which of the two it is remains a real and important question — it is simply a
question for a human, recorded as an adjudication, not inferred from a run.

**`INTENT_CHANGED` is detectable**, but note what makes it so: the *claim
fingerprint* changed, meaning a human already edited what is being asserted.
That is a fact about the recorded use case, not an inference about behaviour.
This is what the T02 table's fourth row was really describing; it was filed under
the wrong heading.

## Why this makes the framework better, not weaker

Calling a semantic change a defect is a **false alarm**: a human looks, says "we
meant that", and updates the claim — which then registers as `INTENT_CHANGED`
with full provenance. Cost: one review.

Calling a defect a semantic change is a **false adaptation**: the thesis dies.

Collapsing the two into one escalating outcome makes the framework err only in
the direction it can afford. The measured consequence is visible in the T08
matrix: 2 of 4 `SEMANTIC` mutations are escalated as `BEHAVIOUR_CHANGED`, which
looks like imprecision and is in fact the design working.

## Consequences

- `docs/TestDriverClassificationDesign.md` decision table updated in place, with
  the original row preserved and marked.
- `TestDriverInitialMilestones.md` M6's four-way path is superseded by this
  finding; the milestone's *intent* (do not normalize defects) is unchanged and
  is met.
- H-004's falsification condition is unaffected: False Adaptation Rate over
  `DEFECT`-labelled mutations. Measured **0/7** at T08.