diff --git a/full-sync.js b/full-sync.js
index 8ba1c735..930f191a 100644
--- a/full-sync.js
+++ b/full-sync.js
@@ -1,16 +1,32 @@
 const appFn = require('./')
 const { FULL_SYNC_NOP } = require('./lib/env')
 const { createProbot } = require('probot')
+const pino = require('pino')
 
 async function performFullSync (appFn, nop) {
-  const probot = createProbot()
+  const logLevel = process.env.LOG_LEVEL || 'info'
+  const logger = pino({
+    level: logLevel,
+    transport: {
+      target: 'pino-pretty',
+      options: {
+        colorize: true,
+        ignore: 'pid,hostname',
+        messageFormat: '{msg}',
+        customColors: 'info:blue,warn:yellow,error:red',
+        levelFirst: true
+      }
+    }
+  })
+
+  const probot = createProbot({ overrides: { log: logger } })
   probot.log.info(`Starting full sync with NOP=${nop}`)
 
   try {
     const app = appFn(probot, {})
     const settings = await app.syncInstallation(nop)
 
-    if (settings.errors && settings.errors.length > 0) {
+    if (settings && settings.errors && settings.errors.length > 0) {
       probot.log.error('Errors occurred during full sync.')
       process.exit(1)
     }
@@ -22,7 +38,13 @@ async function performFullSync (appFn, nop) {
   }
 }
 
-performFullSync(appFn, FULL_SYNC_NOP).catch((error) => {
-  console.error('Fatal error during full sync:', error)
-  process.exit(1)
-})
+// Only run if executed directly (not when imported for testing)
+if (require.main === module) {
+  performFullSync(appFn, FULL_SYNC_NOP).catch((error) => {
+    console.error('Fatal error during full sync:', error)
+    process.exit(1)
+  })
+}
+
+// Export for testing
+module.exports = { performFullSync }
diff --git a/test/unit/full-sync.test.js b/test/unit/full-sync.test.js
new file mode 100644
index 00000000..df37564f
--- /dev/null
+++ b/test/unit/full-sync.test.js
@@ -0,0 +1,37 @@
+/* eslint-disable no-undef */
+const { performFullSync } = require("../../full-sync");
+
+jest.mock("probot", () => ({ createProbot: jest.fn() }));
+jest.mock("pino", () => jest.fn(() => ({ info: jest.fn() })));
+
+describe("full-sync.js", () => {
+  let mockProbot, mockApp;
+
+  beforeEach(() => {
+    mockProbot = { log: { info: jest.fn() } };
+    require("probot").createProbot.mockReturnValue(mockProbot);
+    mockApp = { syncInstallation: jest.fn() };
+    jest.clearAllMocks();
+  });
+
+  it("should pass logger to createProbot via overrides (v14 fix)", async () => {
+    mockApp.syncInstallation.mockResolvedValue({ errors: [] });
+    await performFullSync(jest.fn().mockReturnValue(mockApp), true);
+
+    expect(require("probot").createProbot).toHaveBeenCalledWith(
+      expect.objectContaining({
+        overrides: expect.objectContaining({ log: expect.any(Object) }),
+      }),
+    );
+  });
+
+  it("should handle null settings without crashing (null safety)", async () => {
+    mockApp.syncInstallation.mockResolvedValue(null);
+    await performFullSync(jest.fn().mockReturnValue(mockApp), true);
+
+    // Just verify it completes without throwing
+    expect(mockProbot.log.info).toHaveBeenCalledWith(
+      "Full sync completed successfully.",
+    );
+  });
+});