What problem does it solve? When replacing an application without changing its specification, you cannot verify that the new side matches the current side unless both contain the same data. This Skill builds a shared golden dataset—specifically, an idempotent and deterministic seeding tool (TypeScript or SQL)—so current-vs-new comparisons compare values, not just structure. ## Core Features & Use Cases - Two-phase workflow: Phase A designs logical data and seeds the current test environment; Phase B maps that same logical data onto the new schema and verifies current-new parity per target. - Safety gates: Never touches production, requires both a config-derived gate (db.seedable / dataset_static_paths) and user confirmation before seeding, and keeps secrets out of logs and artifacts. - Versioned datasets: Bumps a dataset version whenever logical data changes so downstream parity baselines can detect staleness. - Use Case: During a legacy system rewrite, generate a seed tool that loads edge-case-rich, realistic test data into the current test DB, then later map and seed the same data into the new schema and verify that all differences match the declared intentional-diff registry. ## Quick Start Ask the AI to run golden-dataset to design and seed a deterministic test dataset for the current environment after replace-strategy setup is complete.