ADR-0002: Clojurust at the boundary only

Status: Accepted (2026-07-15)

Context

Clojurust provides persistent collections, keywords, EDN reading, and an interpreter. The engine could use cljrs-value as its native value type throughout (maximum idiom fidelity), or keep an engine-owned representation and convert at the edges. Index/storage hot paths need a compact, order-preserving byte encoding and cheap comparisons; a general dynamic value type there couples engine performance and layout stability to an external project's internals.

Decision

The engine core (corium-core through corium-db) uses its own Value enum and sortable binary encoding. cljrs appears in exactly three places: value conversion at the public API (corium-cljrs, via cljrs-interop FromValue/IntoValue), EDN text parsing everywhere (cljrs-reader is the only EDN reader in the system), and the sandboxed interpreter for database functions (ADR-0008).

Consequences

• Hot paths (segment compare, merge, join) are memcmp/integer operations, fully under Corium's control; storage format is independent of cljrs versioning.
• A conversion layer must exist and be property-tested for round-trip fidelity; per-call conversion cost at the API edge (amortized — one conversion per call, not per datom touched during execution).
• Rust consumers get a first-class typed API rather than a dynamic-value API.