fix: rollback in-memory key on store failure, add corrupted-data and rollback tests

tests/engine/ChatEngine.test.ts

@@ -778,19 +778,34 @@ describe('ChatEngine', () => {
 
   describe('deleteSetting', () => {
     it('should delete a setting by key', async () => {
+      let capturedTable: any;
       let capturedPredicate: any;
-      vi.mocked(mockLocalDb.delete).mockImplementation(() => ({
-        where: vi.fn((predicate) => {
-          capturedPredicate = predicate;
-          return Promise.resolve();
-        }),
-      } as any));
+      vi.mocked(mockLocalDb.delete).mockImplementation((table: any) => {
+        capturedTable = table;
+        return {
+          where: vi.fn((predicate) => {
+            capturedPredicate = predicate;
+            return Promise.resolve();
+          }),
+        } as any;
+      });
 
       await chatEngine.deleteSetting('opencode_api_key');
 
-      expect(mockLocalDb.delete).toHaveBeenCalled();
+      expect(mockLocalDb.delete).toHaveBeenCalledTimes(1);
+      // Verify the correct table was targeted
+      expect(capturedTable).toBeDefined();
+      // Verify a where predicate was passed
       expect(capturedPredicate).toBeDefined();
     });
+
+    it('should not throw for nonexistent keys', async () => {
+      vi.mocked(mockLocalDb.delete).mockImplementation(() => ({
+        where: vi.fn(() => Promise.resolve()),
+      } as any));
+
+      await expect(chatEngine.deleteSetting('nonexistent_key')).resolves.not.toThrow();
+    });
   });
 
   describe('setSelectedModel', () => {

tests/engine/SecureKeyStore.test.ts

@@ -5,7 +5,7 @@
  * and ChatEngine dependencies.
  */
 
-import { describe, it, expect, beforeEach, vi, afterEach } from 'vitest';
+import { describe, it, expect, beforeEach, vi } from 'vitest';
 
 // Track mock state
 let safeStorageAvailable = true;
@@ -205,4 +205,24 @@ describe('SecureKeyStore', () => {
       expect(mockChatEngine.deleteSetting).toHaveBeenCalledWith('opencode_api_key');
     });
   });
+
+  describe('retrieve with corrupted data', () => {
+    it('throws when stored base64 decodes to invalid ciphertext', async () => {
+      const store = new SecureKeyStore(mockChatEngine as any);
+
+      // Simulate corrupted data: valid base64 but not a valid encrypted buffer
+      mockSettings.set('__encrypted_api_key', Buffer.from('CORRUPT:garbage').toString('base64'));
+
+      await expect(store.retrieve('api_key')).rejects.toThrow('Failed to decrypt');
+    });
+
+    it('throws when stored value is not valid base64', async () => {
+      const store = new SecureKeyStore(mockChatEngine as any);
+
+      // Not valid base64 — Buffer.from tolerates this but decryptString will reject it
+      mockSettings.set('__encrypted_api_key', '!!!not-base64!!!');
+
+      await expect(store.retrieve('api_key')).rejects.toThrow('Failed to decrypt');
+    });
+  });
 });