diff --git a/crates/aura-engine/src/sweep.rs b/crates/aura-engine/src/sweep.rs
index b419627..f155e7e 100644
--- a/crates/aura-engine/src/sweep.rs
+++ b/crates/aura-engine/src/sweep.rs
@@ -118,7 +118,9 @@ impl Space for GridSpace {
     }
 }
 
-/// A structural fault constructing a `GridSpace` — the typed gate before any run.
+/// A structural fault constructing a `GridSpace` or a `RandomSpace` — the shared
+/// typed gate before any run (grid faults: `Arity` / `KindMismatch` / `EmptyAxis`;
+/// random faults: `NonNumericRange` / `RangeKindMismatch` / `EmptyRange`).
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum SweepError {
     /// The number of axes does not equal the param-space slot count.