diff --git a/core/dr-face/src/cluster.rs b/core/dr-face/src/cluster.rs
index 8f578e3..065f81d 100644
--- a/core/dr-face/src/cluster.rs
+++ b/core/dr-face/src/cluster.rs
@@ -370,6 +370,10 @@ impl Ord for Pending {
 struct Engine<'a> {
     faces: &'a [Candidate],
     cal: &'a Calibration,
+    /// The same kernel [`neighbours`] scans with. [`Engine::cross`] is the one
+    /// place a dot product is computed during agglomeration, and it was using
+    /// the portable loop while the scan beside it had the machine's SIMD.
+    dot: neighbours::DotFn,
     min_probability: f32,
     groups: Vec<Group>,
     links: HashMap<(usize, usize), Link>,
@@ -394,6 +398,7 @@ impl<'a> Engine<'a> {
         Self {
             faces,
             cal,
+            dot: neighbours::fastest_dot(),
             min_probability,
             groups,
             links: HashMap::new(),
@@ -581,7 +586,7 @@ impl<'a> Engine<'a> {
         let mut count = 0.0_f64;
         for &i in members {
             for &j in &self.groups[group].members {
-                let cos = neighbours::dot(&self.faces[i].embedding, &self.faces[j].embedding);
+                let cos = (self.dot)(&self.faces[i].embedding, &self.faces[j].embedding);
                 let min_crop = self.faces[i].crop_px.min(self.faces[j].crop_px);
                 sum += self.cal.probability(cos, min_crop, 0.0) as f64;
                 count += 1.0;
diff --git a/core/dr-face/src/neighbours.rs b/core/dr-face/src/neighbours.rs
index 03d0dd8..b6b4213 100644
--- a/core/dr-face/src/neighbours.rs
+++ b/core/dr-face/src/neighbours.rs
@@ -340,7 +340,7 @@ fn loosest_cosine(crop_px: &[f32], cal: &Calibration, min_probability: f32) -> f
 /// A dot product over two equal-length, L2-normalised rows.
 ///
 /// Chosen once per scan rather than per pair — see [`fastest_dot`].
-type DotFn = fn(&[f32], &[f32]) -> f32;
+pub(crate) type DotFn = fn(&[f32], &[f32]) -> f32;
 
 /// The widest dot product this machine can actually run.
 ///
@@ -369,7 +369,7 @@ type DotFn = fn(&[f32], &[f32]) -> f32;
 /// last bit between them. That only matters for a pair sitting exactly on the
 /// threshold, and the portable kernel already sums in eight accumulators rather
 /// than one, so the module was never bit-comparable with a naive sum.
-fn fastest_dot() -> DotFn {
+pub(crate) fn fastest_dot() -> DotFn {
     #[cfg(target_arch = "x86_64")]
     {
         if std::arch::is_x86_feature_detected!("avx2") && std::arch::is_x86_feature_detected!("fma")