demo-data-and-seedinglisted

# Demo data: safe to create, safe to remove, and worth looking at **Read [`references/DEMO-DATA-AND-SEEDING.md`](references/DEMO-DATA-AND-SEEDING.md) before applying any of this.** That file is the standard; everything below it is a summary to help you decide whether this skill applies and to check your work afterwards. Reference-architecture principles: P5, P13. ## What this standard covers - Namespace demo data, and enforce it at the receiver - Reset clears the namespace, everywhere it was written - Seed through the running system, not around it - Deterministic by default - Two tiers, and what each one proves - Personas: demo data should tell a story ## Failure modes | Symptom | Cause | |---|---| | A reset deleted real data | Cleanup matched on something other than a reserved namespace — a date range, "everything", a guess (§1) | | Seeded ids overwrote real records | The namespace was a convention the writing tool honoured, never enforced at the receiver (§1) | | Cleared demo data comes back | Reset cleared one store; the data was written to two (§2) | | The demo shows a state the product cannot actually produce | Seeded straight into the database, bypassing the validation and derived values the service applies (§3) | | A screenshot cannot be reproduced | Unseeded RNG, so every run produces a different dataset (§4) | | Re-running the seeder doubles the data | Non-idempotent: new ids each run instead of stable namespaced ones (§4) | | Ingest is broken and every demo st