Constant FIRST_USER_ENTITY_ID 

pub const FIRST_USER_ENTITY_ID: u64 = 1024; // 1_024u64

The first entity-id handed to user-inserted data. Ids 1..FIRST_USER_ENTITY_ID are reserved for the internal collection-descriptor and config-default entities the engine seeds at boot, so the first user-inserted rid is a STABLE, documented value regardless of how many config defaults a build ships.

Before this floor existed the offset drifted upward by one for every config default added (101 → 114 over time), silently breaking the documented file-format invariant (#1369). The boot sequence bumps the allocator up to this floor after seeding internals; it only ever raises the counter, so a database that already holds user data is untouched. Mirrors FIRST_USER_LABEL_ID in the graph label registry.