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
Index summary	Demotes EXP-M4→EXP-R3 (change/counterfactual summaries); removes from Regulated mandatories; pre-release ID-removal exception.
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

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.
Remove EXP-M4 from Regulated mandatoryCheckIds (Regulated 52→51; tier3-only 14→13). Core unchanged (38).
Remove EXP-M4 from explainability mandatoryChecks in aprf-spec.json; add EXP-R3 under recommendedChecks.
Pass condition unchanged in substance: last material model/prompt promotion retains a change or counterfactual summary; attest measuredAt ≤90d.
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

Problem and affected parties
Proposed change stated
SemVer impact justified
Compatibility / deprecation plan
Checks remain measurable
Crosswalk impact noted
Security / safety considered
Open questions listed

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