Temporal-pyramid L1/L2 durable aggregation lane + velocity fields

Context

Leaf B of Epic #12679's implementation decomposition (map: https://github.com/neomjs/neo/issues/12679#issuecomment-4862079789). Filed pre-Accepted per ADR 0005 §2.3 for planning visibility. Sequenced after Leaf A (#14433 — the storage substrate this lane writes into).

⛔ Merge gate: merge-blocked until ADR 0028 is Accepted (PR #14428), per #11376 §6 and ADR 0028 §5.

The Problem

The durable tiers do not exist: no lane aggregates sessions (L1) and days (L2) into the temporal-summary collection, and the deterministic velocity fields (the substrate's answer to the "150+ PRs a week" V-B-A failure class) have no producer.

The Architectural Reality

Bound by ADR 0028 (re-verify Accepted at claim):

• §2.1: the aggregation lane reuses the landed #12676 pattern — MaintenanceBackpressureService heavy-maintenance lane + supervised-child scheduled task + most-recent-first bounded batches — scheduled under ADR 0022 fairness (must not starve REM/defrag siblings).
• §2.4: L1/L2 records carry the deterministic velocity fields (mergedPrs, devCommits, sessionsPerAgent, highImpactSessions, adrsLanded, sandboxesGraduated), each bound to its named source substrate at implementation; prose is never the source of truth. Velocity fields are folded into this leaf (not separate) because they ship with the aggregation write path — a separate metrics leaf would re-open the same files (fold rationale in the map).
• §2.6: per-agent partitions + one unified track with attribution.
• §2.3 boundary: writes go through the Leaf-A schema (SUMMARY_DAILY labels via this deterministic lane only — never extractor-prompt widening).
• Retention/versioning policy: owned here, within the version metadata field.
• New .mjs placement via structural-pre-flight at claim (likely ai/daemons/ scheduled-task + ai/services/ territory; contract stays directory-agnostic).

The Fix

One PR: the L1 (per-session) + L2 (daily) aggregation lane writing collection records + SUMMARY_DAILY labels, velocity fields populated from named sources, retention/versioning policy, scheduled under the backpressure/fairness substrate. No L3–L5 logic (Leaf C), no consumer surface.

Contract Ledger Matrix

Decision Record impact

depends-on ADR 0028 (Accepted-gate) · aligned-with ADR 0022 (scheduling fairness) · consumes Leaf A (#14433) schema.

Acceptance Criteria

• L1 + L2 aggregation runs as a supervised, backpressure-leased scheduled lane (most-recent-first, bounded batches).
• Every §2.4 velocity field populated from its named source; per-field source binding documented; no prose-derived values.
• Per-agent + unified partition tracks written per §2.6.
• SUMMARY_DAILY labels written only by this lane (extractor untouched).
• Retention/versioning policy defined + tested within the version field.
• PR held un-merge-ready until ADR 0028 Accepted; gate stated in the PR body.
• Cross-family review before merge.

Out of Scope

• L3–L5 synthesis (Leaf C). Consumer surfaces. Schema creation (Leaf A). Backfill of deep history (a follow-up policy decision once the lane is proven forward-running).

Avoided Traps

• Durable compression above L2 — rejected (ADR 0028 anti-anchor; photocopy cascade).
• A universal PR impact score — rejected (§2.5; named sources only).
• Separate velocity-metrics leaf — rejected (fold rationale above).
• New cron per tier×partition — rejected (the L3–L5-dynamic shape exists precisely to avoid it).

Related

Parent: #12679 (native link on file). Authority: ADR 0028 (PR #14428). Depends-on: #14433 (Leaf A). Sibling: Leaf C (L3–L5 synthesis). Pattern source: PR #12676 (merged 2026-06-07).

Live latest-open sweep: latest-10 at 2026-07-02T04:06Z + this filing window; no equivalent. A2A sweep: all-states at 04:06Z; no competing claim. Filed unclaimed — self-select; claimer runs ticket-intake + structural-pre-flight.

Origin Session ID: 2251c81c-1446-4723-86b3-479322bbcc95 Retrieval Hint: "temporal pyramid Leaf B L1 L2 durable aggregation velocity fields backpressure"