diff --git a/src/test/java/puzzle/PerformanceTest.java b/src/test/java/puzzle/PerformanceTest.java
new file mode 100644
index 0000000..765be6c
--- /dev/null
+++ b/src/test/java/puzzle/PerformanceTest.java
@@ -0,0 +1,66 @@
+package puzzle;
+
+import lombok.val;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import puzzle.SwedishGenerator.Rng;
+import puzzle.SwedishGenerator.Slotinfo;
+
+import java.util.Locale;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static puzzle.SwedishGenerator.fillMask;
+
+public class PerformanceTest {
+
+    @Test
+    @Disabled
+    void testPerformance() {
+        val rng = new Rng(42);
+        val dict = DictData.DICT;
+
+        // 1. Stress test Clue Generation (Mask Generation)
+        System.out.println("[DEBUG_LOG] --- Mask Generation Performance ---");
+        int[] clueSizes = {20, 25, 30};
+        for (int size : clueSizes) {
+            long t0 = System.currentTimeMillis();
+            val masker = new Masker(rng, new int[SwedishGenerator.STACK_SIZE], Masker.Clues.createEmpty());
+            // Increased population and generations for stress
+            val mask = masker.generateMask(size, 200, 100, 50);
+            long t1 = System.currentTimeMillis();
+            double duration = (t1 - t0) / 1000.0;
+            System.out.printf(Locale.ROOT, "[DEBUG_LOG] Size %d (pop=200, gen=100): %.3fs%n", size, duration);
+            // Basic sanity check: should not take forever
+            assertTrue(duration < 10.0, "Mask generation took too long for size " + size);
+        }
+
+        // 2. Stress test Word Filler
+        System.out.println("[DEBUG_LOG] \n--- Word Filler Performance ---");
+        for (int size : clueSizes) {
+            val masker = new Masker(rng, new int[SwedishGenerator.STACK_SIZE], Masker.Clues.createEmpty());
+            val mask = masker.generateMask(size, 100, 50, 20);
+
+            val slots = Masker.extractSlots(mask, dict.index());
+            val slotInfo = Masker.scoreSlots(slots);
+            val grid = mask.toGrid();
+
+            long t0 = System.currentTimeMillis();
+            // Try to fill multiple times to get a better average
+            int iterations = 3;
+            long totalNodes = 0;
+            long totalBacktracks = 0;
+            int successCount = 0;
+            for (int i = 0; i < iterations; i++) {
+                val result = fillMask(rng, slotInfo, grid.copy(), false);
+                if (result.ok()) successCount++;
+                totalNodes += result.nodes();
+                totalBacktracks += result.backtracks();
+            }
+            long t1 = System.currentTimeMillis();
+            double totalDuration = (t1 - t0) / 1000.0;
+
+            System.out.printf(Locale.ROOT, "[DEBUG_LOG] Size %d: %d/%d SUCCESS | avg nodes=%d | avg backtracks=%d | total time=%.3fs%n",
+                    size, successCount, iterations, totalNodes / iterations, totalBacktracks / iterations, totalDuration);
+        }
+    }
+}