diff --git a/server/db.js b/server/db.js
index bf0e99e..1eaf6ab 100644
--- a/server/db.js
+++ b/server/db.js
@@ -151,11 +151,13 @@ export function updateInstance(vmid, data) {
 }
 
 export function deleteInstance(vmid) {
-  return db.prepare('DELETE FROM instances WHERE vmid = ?').run(vmid);
+  db.prepare('DELETE FROM instance_history WHERE vmid = ?').run(vmid);
+  db.prepare('DELETE FROM instances WHERE vmid = ?').run(vmid);
 }
 
 export function importInstances(rows) {
   db.exec('BEGIN');
+  db.exec('DELETE FROM instance_history');
   db.exec('DELETE FROM instances');
   const insert = db.prepare(`
     INSERT INTO instances
diff --git a/tests/db.test.js b/tests/db.test.js
index de5cef4..ee64d3a 100644
--- a/tests/db.test.js
+++ b/tests/db.test.js
@@ -164,6 +164,19 @@ describe('deleteInstance', () => {
     expect(getInstance(1)).toBeNull();
     expect(getInstance(2)).not.toBeNull();
   });
+
+  it('clears history for the deleted instance', () => {
+    createInstance({ ...base, name: 'a', vmid: 1 });
+    deleteInstance(1);
+    expect(getInstanceHistory(1)).toHaveLength(0);
+  });
+
+  it('does not clear history for other instances', () => {
+    createInstance({ ...base, name: 'a', vmid: 1 });
+    createInstance({ ...base, name: 'b', vmid: 2 });
+    deleteInstance(1);
+    expect(getInstanceHistory(2).length).toBeGreaterThan(0);
+  });
 });
 
 // ── importInstances ───────────────────────────────────────────────────────────
@@ -183,6 +196,12 @@ describe('importInstances', () => {
     importInstances([]);
     expect(getInstances()).toEqual([]);
   });
+
+  it('clears history for all replaced instances', () => {
+    createInstance({ ...base, name: 'old', vmid: 1 });
+    importInstances([{ ...base, name: 'new', vmid: 2 }]);
+    expect(getInstanceHistory(1)).toHaveLength(0);
+  });
 });
 
 // ── instance history ─────────────────────────────────────────────────────────