Epic: drift discoverability

[kyle-sexton]

Brief

TLDR

Three small items that make the drift-detection lanes findable and schedulable, and close a silent second way in how a delta baseline is persisted. Router text in the codebase-health audit Boundary, a routine fan-out on the ci-cron surface, and moving the instruction-placement delta baseline onto the artifact protocol.

Goal

An operator who reaches one drift lane can find the others, a scheduled surface sweeps the delta lanes without a human remembering to, and both delta skills persist their baseline the same way.

Constraints

• Every cross-skill reference is presence-gated.
• The listing-entry cap for a skill description is respected; router text does not inflate the description past it.
• Routine instruction content lives in the tracked leaf per the routine catalog's instruction-provenance rule.
• The scheduling surface is ci-cron. No cloud schedule surface.
• Reuse-or-replace: the artifact-protocol baselines slot is the established way, so the ephemeral state-key becomes a replacement, not a parallel second way.

Acceptance criteria

• The codebase-health audit Boundary names each sibling drift lane with one line on what it owns, and every reference is presence-gated.
• The doc-freshness-sweep routine leaf (or a sibling drift-delta-sweep row) names the instruction-placement delta, overengineering delta, and codebase-health audit skills as its fan-out on the ci-cron surface.

Amended 2026-09-06 (planning slice #3809). Criterion 2 is satisfied by a sibling v1 catalog row drift-delta-sweep with its own leaf, not by extending the doc-freshness-sweep leaf (extending would change what the ratified identity doc-freshness-sweep/advisory authorizes without an org re-reviewing it). "On the ci-cron surface" is satisfied in the shipped contract this way: the leaf states the fan-out's run predicate as a fact (the delta lanes compare only with a resolvable branch identity and a memory-tier home persisted across runs) and gives one illustrative binding, a scheduled job on the CI-orchestration home whose runner restores that home, which guided setup records as the ci-cron scheduler class; the catalog's hosting stance keeps the actual surface binding org-owned, the leaf excludes no surface, and nothing in this container registers one, so the "no cloud schedule surface" constraint is met by registering nothing. The reuse-or-replace constraint also covers the overengineering plugin's recurring-wiring contract, which the leaf reconciles with rather than diverging from (a routine's tracker-held queue item has that contract's preferred recurring-work-item durability, minted by a scheduled tick that is itself an enforcement-surface item the report must justify). A reviewer ruling is open: v1 rests on the class-level pattern (report-only drift-watch rows already recur in this repository's schedule) with no run record for these three lanes together; a join: ruling would ship no leaf and leave this criterion unsatisfiable as written. Criteria 1, 3, and 4 (#3810 shipped via PR #3828, #3811 via PR #3831) are unchanged by this note. Deferred questions raised by the planning slice: a generator need for sibling-plugin presence and a persisted home; an unattended token for the codebase-health audit; a consumer-side binding of the class for this repository; and the v1 ruling above.

• The instruction-placement delta skill persists its baseline in the artifact-protocol baselines slot, and declined findings survive across worktrees.
• The instruction-placement delta skill carries its own artifact-protocol reference documenting its participation.

Captured assumptions

• The seven sibling drift lanes named in the router are the complete current set; new lanes are added as they land.
• The ci-cron surface is where a fleet-wide drift sweep belongs; nobody needs a cloud-scheduled equivalent.

Out-of-scope

• A cloud schedule routine for drift sweeping.
• Phase-end nudges about concepts that were skipped: nothing was built, so there is nothing to suggest.
• Changing what any delta skill detects. This lane is discoverability and persistence only.

Deferred questions

• Should generate-identity-prerequisites.mjs gain needs for "sibling plugin installed" and "memory-tier home persisted across runs", so the resolver stops over-reporting supported for drift-delta-sweep? (raised by autonomy: plan drift-delta routine extension of doc-freshness-sweep on ci-cron #3809)
• Should /codebase-health:audit gain an unattended token, as /overengineering:delta has, so a scheduled run never hits its target-ask and twenty-file confirm stops? Outside this container's scope. (raised by autonomy: plan drift-delta routine extension of doc-freshness-sweep on ci-cron #3809)
• Should this repository bind the new class for itself (a .github/recurring-schedule.json row per the overengineering recurring-wiring Shape 4, or an autonomy binding once the runner ships)? (raised by autonomy: plan drift-delta routine extension of doc-freshness-sweep on ci-cron #3809)
• v1 versus join: proven recurring manual pattern for drift-delta-sweep: the row ships as v1 because this Brief requires a leaf; a PR-review ruling the other way re-slices autonomy/routines: add the drift-delta-sweep v1 class whose leaf fans to instruction-placement:delta, overengineering:delta, codebase-health:audit #3819. (raised by autonomy: plan drift-delta routine extension of doc-freshness-sweep on ci-cron #3809)

Execution shape: per-item PRs

[kyle-sexton]

Closing this container: all four acceptance criteria in the Brief are satisfied on merged main (794fb6077).

What the effort delivered. /codebase-health:audit now carries a Boundary, the adjacent drift lanes section that names all seven sibling drift lanes with one line each on what that lane owns, framed as an operator router rather than a dispatch list, so a request belonging to another lane is reported as uncovered and routed instead of having claim extraction run over it. The routine catalog gained a sibling drift-delta-sweep v1 class with its own normative leaf, fanning out to /instruction-placement:delta, /overengineering:delta, and /codebase-health:audit, each presence-gated with a stated fallback, with a stateless ISO-week rotation over the enforcement layers and the audit dimensions, and with the run predicate stated as a fact of the class plus one illustrative ci-cron binding, leaving the actual surface binding org-owned. The instruction-placement delta lane's state was split across the right tiers: the comparison spine now lives in the lifecycle artifact protocol's baselines/ slot, branch-keyed in the memory tier, while an operator's declined findings ride the tracked .claude/instruction-placement.md suppression surface, which is what actually carries a judgment across checkouts. The retired lib/state-key.sh was removed rather than left as a parallel second way, and the plugin now ships its own copy of the artifact-protocol reference under the byte-identity gate.

Shipping PRs. #3828 (criterion 1), #3889 (criteria 3 and 4), #3903 (criterion 2). The planning slice #3809 closed without a PR by design, because the contract-slice prune gate red-lines a PR carrying paths under docs/topics/; its plan is durable in the #3819 body and in #3809's closing comment.

What this close-out review verified, rather than accepted on description. Each criterion was checked against the shipped files, not against PR bodies or changelog entries. The seven router rows were confirmed to name owners that exist on disk, and the two behavioral claims the router makes about /review:fanout were checked against that skill's own mode files: the default lifecycle-tiered mode never dispatches doc-drift-detector, and only run-everything does. The leaf's claims about its fan-out targets were checked against those targets: /overengineering:delta does accept unattended and all ten layer tokens, and /codebase-health:audit does carry the twenty-file confirm threshold and the four dimension flags the leaf routes around. Commands run: node scripts/validate-plugin-contracts.mjs (pass, 3385 plugin files checked, which is the gate enforcing byte-identity of the six artifact-protocol copies, independently confirmed by hashing all six to a single digest); generate-identity-prerequisites.mjs, which reported the generated emission already in sync; check-prerequisite-resolution-slice.test.sh (4 passed, 0 failed); instruction-placement/scripts/precompute.sh audit and precompute.test.sh (23 cases, 0 failures); and skill-quality/scripts/check-skill.sh against both changed skills (both PASS, 0 errors).

Two items for follow-up, neither blocking. The Boundary's quotation of /discipline:recheck-against-upstream at plugins/codebase-health/skills/audit/SKILL.md:74-75 drops "per the method doc" from a sentence presented inside quotation marks; the substance is right, but the quote should be made verbatim or unquoted. And the 2026-09-06 amendment in this body credits PR #3831 for #3811, which was closed and superseded; the merged PR is #3889. The four deferred questions the Brief records stay open and are unaffected by this closure.