Authoritative protocol for querying the Memory Core before diagnosing regressions or proposing non-trivial architectural claims. Prevents re-derivation of prior reasoning by surfacing cross-session, cross-harness context via semantic search. Triggers: Use this skill when (1) the user reports a regression symptom ("used to work", "suddenly broken", surprise validation failures, schema mismatches, "additionalProperties" rejections), OR (2) you are about to propose an architectural claim, roadmap, or comparison against external work where prior sessions may have already mapped the territory, OR (3) you are about to begin an implementation or a PR-review — a cheap 3–10-call prior-art sweep before the first design sentence or review verdict.