APRF-RFC-0008: Demote explainability EXP-M4 to recommended (EXP-R3)

Field	Value
Status	accepted
Author(s)	StackRail (working-draft publisher)
Created	2026-08-01
SemVer impact	MINOR
Related	APRF-RFC-0007 (pre-release M→R pattern)

Problem

EXP-M4 required material model/prompt promotions to retain a change or counterfactual summary as a Regulated mandatory (`must`, `minCriticality: 3`, `requiredFromLevel: 5`). That over-weights promotion narrative documentation relative to production-blocking explainability gates:

Stronger / adjacent control	What it already proves
EXP-M1	Factual/high-stakes RAG answers carry resolvable citations
EXP-M2	Operators reconstruct decision paths within a documented budget
EXP-M3	Explanation payloads redact/block secrets and unauthorized data
PRM-M2	Prompt changes link to review/eval evidence
CHG-M1	AI artifact change records / registry retention
EVL-M4	Shadow/A-B or cutover evaluation for promotions

Change/counterfactual summaries remain valuable Level-5 explainability maturity, but failing Regulated for a missing promotion narrative when citation provenance, path reconstruction, and explanation hygiene already hold creates false fails for teams with staged promotion UX and eval-gated releases.

Proposal

1. Demote EXP-M4 → EXP-R3 (recommended `should` language; hybrid detection via `repo-ai-change-summary` / `ai-change-summary` collector). Reuses the recommended slot vacated when the regulated explainability matrix was renumbered to EXP-R2.

2. Remove EXP-M4 from Regulated `mandatoryCheckIds` (Regulated 52→51; tier3-only 14→13). Core unchanged (38).

3. Remove EXP-M4 from explainability mandatoryChecks in `aprf-spec.json`; add EXP-R3 under recommendedChecks.

4. Pass condition unchanged in substance: last material model/prompt promotion retains a change or counterfactual summary; attest `measuredAt` ≤90d.

5. Keep EXP-M1–M3 as the explainability mandatory spine (citations, path reconstruction, explanation hygiene).

Alternatives considered

- Soften passCondition but keep Regulated mandatory — rejected; still blocks Tier-3 for promotion-narrative maturity.

- Demote in place (`gate: recommended` on EXP-M4) — rejected; recommended Checks use the `*-R*` namespace.

- Merge into PRM-M2 / CHG-M1 — rejected; those prove review/eval linkage and registry retention, not a human-readable change/counterfactual narrative.

- Merge into EXP-R1 — rejected; EXP-R1 centers on user-facing rationale for material decisions, not version-to-version promotion summaries.

Compatibility

Change	Impact
EXP-M4 removed; EXP-R3 added	Catalog mandatory −1; recommended +1; total Checks unchanged (178)
Core	Unchanged (38)
Regulated	52→51 (EXP-M4 removed)
Crosswalk / relatedRules	Remapped EXP-M4 → EXP-R3
Collector / plugin	`ai-change-summary` maps to EXP-R3

SemVer: MINOR — profile gate set and Check ID remapping while still on working-draft `0.10.x`.

Pre-release exception: no tagged release yet — EXP-M4 YAML removed rather than deprecated stub. Recorded in `id-gaps.md`. After first tagged release, future demotions must use `deprecated` + `replacedBy`.

Security considerations

No weakening of citation provenance, decision-path reconstruction, or explanation secret/PII hygiene. Residual risk is slower incident/dispute explanation of what changed in the last model/prompt promotion; mitigated by high-severity EXP-R3 plus PRM-M2/CHG-M1/EVL-M4 siblings.

Open questions

- Should Regulated later re-include promotion change summaries as additional mandatory once Level-5 release-explainability maturity is ratified?

- Should empty “N/A” summaries for non-behavioral promotions be an explicit named-exception path rather than fail?

Checklist

- [x] Problem and affected parties

- [x] Proposed change stated

- [x] SemVer impact justified

- [x] Compatibility / deprecation plan

- [x] Checks remain measurable

- [x] Crosswalk impact noted

- [x] Security / safety considered

- [x] Open questions listed

Comment window: 14 days from `Created` (working-draft quorum applies). Interim contact: see `/aprf/rfc/`.