firehose_stats now always compiles: shared kind enums and timings live in kinds.rs; the real atomic-counter impls are gated behind firehose-diagnostics; a noop mirror of ZST types with inline empty recorders takes their place otherwise. StatsInstant (Instant when enabled, ZST returning Duration::ZERO when not) keeps timing call sites unconditional at zero cost. ~100 inline cfg sites across the ingest hot path (firehose.rs, relay worker/context/handlers) removed; the read side (snapshot endpoints) stays gated at its composition roots.