NEVER Do (collection landmines)

NEVER reuse or omit stable collectible IDs — Duplicate IDs double-count or overwrite; missing IDs break completion % and saves.
NEVER count the same Area overlap twice — body_entered can re-fire on re-entry; gate with "already collected" / one-shot disable of monitoring.
NEVER persist NodePaths as the identity of collectibles — Paths break on scene moves; save IDs (StringName / int), not get_path().
NEVER soft-lock the last item — If compass / spawn logic depends on "remaining > 1", the final pickup becomes unfindable.
NEVER store hunt progress only in scene-local nodes — Level reload wipes progress; keep collected set in collection_manager.gd + save.
NEVER queue_free() collectibles with zero juice and no ID commit — Commit ID first (signal), then VFX, then free.
NEVER scale collectible collision shapes non-uniformly — Breaks overlap math; edit shape resources.
NEVER hardcode spawn positions in code — Use Marker3D / designer points with hidden_item_spawner.gd.
NEVER drive collection truth from UI silhouettes — Archive UI mirrors manager state; manager is authoritative.
NEVER load massive levels synchronously on hunt complete — use threaded ResourceLoader (see references).
NEVER manipulate SceneTree from worker threads — call_deferred only.

godot-game-loop-collection