diff --git a/internal/core/duplicate_detector.go b/internal/core/duplicate_detector.go
index 2a2666a52..abebf0ce0 100644
--- a/internal/core/duplicate_detector.go
+++ b/internal/core/duplicate_detector.go
@@ -1,6 +1,7 @@
 package core
 
 import (
+	"math"
 	"sort"
 	"strings"
 )
@@ -26,6 +27,13 @@ func LevenshteinDistance(a, b string) int {
 	if len(b) == 0 {
 		return len(a)
 	}
+	// Guard allocation arithmetic from integer overflow.
+	if len(b) > math.MaxInt-1 {
+		return len(b)
+	}
+	if len(a) > math.MaxInt-1 {
+		return len(a)
+	}
 
 	// Use two rows instead of full matrix for space efficiency.
 	prev := make([]int, len(b)+1)