diff --git a/pkg/kthena-router/datastore/store.go b/pkg/kthena-router/datastore/store.go
index 852ec52dd..97beab116 100644
--- a/pkg/kthena-router/datastore/store.go
+++ b/pkg/kthena-router/datastore/store.go
@@ -981,6 +981,11 @@ func selectFromWeightedSlice(weights []uint32) int {
 		totalWeight += int(weight)
 	}
 
+	// Guard against divide-by-zero when all weights are zero
+	if totalWeight == 0 {
+		return 0
+	}
+
 	randomNum := rng.Intn(totalWeight)
 
 	for i, weight := range weights {
diff --git a/pkg/kthena-router/datastore/store_test.go b/pkg/kthena-router/datastore/store_test.go
index 20f1ca088..a22f6c6bb 100644
--- a/pkg/kthena-router/datastore/store_test.go
+++ b/pkg/kthena-router/datastore/store_test.go
@@ -1217,3 +1217,69 @@ func TestStoreMatchModelServer(t *testing.T) {
 		})
 	}
 }
+
+func TestSelectFromWeightedSlice(t *testing.T) {
+	tests := []struct {
+		name           string
+		weights        []uint32
+		expectPanic    bool
+		expectedResult int // only checked when not expecting panic and result is deterministic
+		checkRange     bool
+		minResult      int
+		maxResult      int
+	}{
+		{
+			name:           "all weights zero does not panic",
+			weights:        []uint32{0, 0, 0},
+			expectPanic:    false,
+			expectedResult: 0,
+		},
+		{
+			name:           "single zero weight does not panic",
+			weights:        []uint32{0},
+			expectPanic:    false,
+			expectedResult: 0,
+		},
+		{
+			name:        "normal weighted selection returns valid index",
+			weights:     []uint32{1, 2, 3},
+			expectPanic: false,
+			checkRange:  true,
+			minResult:   0,
+			maxResult:   2,
+		},
+		{
+			name:           "single non-zero weight returns index 0",
+			weights:        []uint32{5},
+			expectPanic:    false,
+			expectedResult: 0,
+		},
+		{
+			name:           "empty weights returns 0",
+			weights:        []uint32{},
+			expectPanic:    false,
+			expectedResult: 0,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.expectPanic {
+				assert.Panics(t, func() {
+					selectFromWeightedSlice(tt.weights)
+				})
+				return
+			}
+
+			assert.NotPanics(t, func() {
+				result := selectFromWeightedSlice(tt.weights)
+				if tt.checkRange {
+					assert.GreaterOrEqual(t, result, tt.minResult)
+					assert.LessOrEqual(t, result, tt.maxResult)
+				} else {
+					assert.Equal(t, tt.expectedResult, result)
+				}
+			})
+		})
+	}
+}