Two Pre-Registered Benchmarks for Audit-Native RAG: RAB (EU AI Act 10/12/19) + LRB (Time-Travel Retrieval)

Most RAG demos answer "what's the right chunk?" Very few can answer the two questions a regulator or an auditor will actually ask: Replay this decision — show me the exact, complete record of how this answer was produced. Reconstruct the past — what did your system know at the moment it answered, not what it knows now? I got tired of hand-waving at both, so I shipped two pre-registered, deterministic benchmarks alongside JAMES , my local-first, audit-native Graph-RAG. Pre-registered means the metrics, scenarios, and decision rules were locked before the numbers came in — no post-hoc story-fitting. RAB — Replayable-Audit Benchmark RAB measures whether your audit trail is good enough to replay a decision, with three deterministic metrics: Metric What it checks EU AI Act AC — Audit Completeness Is every decision-relevant event logged? Art. 10 RF — Replay Fidelity Can you re-derive the answer from the log alone? Art. 12 PC — Provenance Coverage Does every claim trace to a source? Art. 19 The three metrics map verbatim to EU AI Act Articles 10, 12, and 19 — record-keeping obligations that apply from 2026-08-02 (per Article 113). Scenario S1 result: AC RF PC JAMES 1.000 1.000 1.000 Baseline-0 0.275 0.000 0.000 (vanilla default-logging) The gap is the whole point. "We have logs" (AC 0.275) is not the same as "we can replay the decision" (RF 0). Default application logging gets you a partial event trail and zero replay/provenance — which is exactly the failure mode an Article 12 audit would surface. LRB — Lifecycle Retrieval Benchmark RAG facts go stale. A policy is superseded, a price changes, a spec is revised. LRB asks: when you query as of a point in time, do you retrieve the fact that was valid then , or whatever overwrote it? Three systems compared: V — Vanilla : no time handling. N — Naive-supersede : newest fact wins. J — JAMES : validity-window retrieval ( reconstruct_graph_at(t) ). The R@1 ordering V < N < J holds across 4 model families × 4 scale points (a 12.5×