reversal/tokeniser.go

@@ -113,16 +113,16 @@ func WithSignals() TokeniserOption {
 }
 
 // WithWeights overrides the default signal weights for disambiguation.
-// All signal keys must be present; omitted keys silently disable those signals.
+// Omitted keys keep their default weights so partial overrides stay safe.
 func WithWeights(w map[string]float64) TokeniserOption {
 	return func(t *Tokeniser) {
 		if len(w) == 0 {
 			t.weights = nil
 			return
 		}
-		// Copy the map so callers can safely reuse or mutate their input after
-		// constructing the tokeniser.
-		copied := make(map[string]float64, len(w))
+		// Start from the defaults so callers can override only the weights they
+		// care about without accidentally disabling the rest of the signal set.
+		copied := defaultWeights()
 		for key, value := range w {
 			copied[key] = value
 		}

reversal/tokeniser_test.go

@@ -977,6 +977,18 @@ func TestWithWeights_CopiesInputMap(t *testing.T) {
 	}
 }
 
+func TestWithWeights_PartialOverrideKeepsDefaults(t *testing.T) {
+	setup(t)
+	tok := NewTokeniser(WithWeights(map[string]float64{
+		"verb_auxiliary": 0.25,
+	}))
+
+	tokens := tok.Tokenise("The commit")
+	if tokens[1].Type != TokenNoun {
+		t.Fatalf("with partial weights, 'commit' Type = %v, want TokenNoun", tokens[1].Type)
+	}
+}
+
 // --- Benchmarks ---
 
 func benchSetup(b *testing.B) {