diff --git a/tests/computeScore.nonstack.test.ts b/tests/computeScore.nonstack.test.ts
new file mode 100644
index 0000000..c7d0a41
--- /dev/null
+++ b/tests/computeScore.nonstack.test.ts
@@ -0,0 +1,39 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { createTempDir, cleanupTempDir, createTempJsonlPath, createTempDbPath } from './test-utils.js';
+import { WorklogDatabase } from '../src/database.js';
+
+describe('computeScore non-stacking invariant', () => {
+  let tempDir: string;
+  let dbPath: string;
+  let jsonlPath: string;
+  let db: WorklogDatabase;
+
+  beforeEach(() => {
+    tempDir = createTempDir();
+    dbPath = createTempDbPath(tempDir);
+    jsonlPath = createTempJsonlPath(tempDir);
+    db = new WorklogDatabase('TEST', dbPath, jsonlPath, true, true);
+  });
+
+  afterEach(() => {
+    db.close();
+    cleanupTempDir(tempDir);
+  });
+
+  it('applies only the in-progress boost (not ancestor boost) when item is itself in-progress', async () => {
+    // Create a high-priority open item, then an in-progress parent (medium)
+    const highOpen = db.create({ title: 'High open item', priority: 'high' });
+    // ensure a deterministic createdAt ordering
+    await new Promise(resolve => setTimeout(resolve, 10));
+    const parent = db.create({ title: 'In-progress parent', priority: 'medium', status: 'in-progress' });
+    db.create({ title: 'In-progress child', priority: 'medium', status: 'in-progress', parentId: parent.id });
+
+    db.reSort();
+
+    const updatedHighOpen = db.get(highOpen.id)!;
+    const updatedParent = db.get(parent.id)!;
+
+    // With correct non-stacking: highOpen should sort above parent
+    expect(updatedHighOpen.sortIndex).toBeLessThan(updatedParent.sortIndex);
+  });
+});