`[2026-06-15]` **"Sindra hasn't been registered" was an under-verified inference — WRONG.** Concluded it from grepping ratatoskr's CODE (`sindra` absent from `src/`), but Tier-3 registration is SERVER-SIDE (`POST /agents/define`) — a code grep structurally can't see it. **Rule: to check whether a Tier-3 agent exists, query the Worldtree instance, never the consumer repo's code.** (Extended 2026-06-17: even `GET /agents` can't see consumer agents; only `GET /agents/<owner>:<name>` with the owner key does.)