diff --git a/src/gateway/sync.test.ts b/src/gateway/sync.test.ts
index f062ffed7..33bd8dadd 100644
--- a/src/gateway/sync.test.ts
+++ b/src/gateway/sync.test.ts
@@ -39,7 +39,7 @@ describe('syncToR2', () => {
   });
 
   describe('sanity checks', () => {
-    it('returns error when source has no config file', async () => {
+    it('returns error with diagnostics when config file missing and gateway not running', async () => {
       const { sandbox, startProcessMock } = createMockSandbox();
       startProcessMock
         .mockResolvedValueOnce(createMockProcess('s3fs on /data/moltbot type fuse.s3fs\n'))
@@ -52,6 +52,33 @@ describe('syncToR2', () => {
 
       expect(result.success).toBe(false);
       expect(result.error).toBe('Sync aborted: no config file found');
+      expect(result.details).toContain('Gateway process is not running');
+    });
+
+    it('returns error with diagnostics when config file missing but gateway is running', async () => {
+      const { sandbox, startProcessMock, listProcessesMock } = createMockSandbox();
+      listProcessesMock.mockResolvedValue([
+        { command: 'start-openclaw.sh', status: 'running', id: 'proc_123' },
+      ]);
+      startProcessMock
+        .mockResolvedValueOnce(createMockProcess('s3fs on /data/moltbot type fuse.s3fs\n'))
+        .mockResolvedValueOnce(createMockProcess('', { exitCode: 1 })) // No openclaw.json
+        .mockResolvedValueOnce(createMockProcess('', { exitCode: 1 })) // No clawdbot.json
+        // Diagnostic commands:
+        .mockResolvedValueOnce(createMockProcess('total 0')) // ls /root/.openclaw/
+        .mockResolvedValueOnce(createMockProcess('No such file or directory')) // ls R2 backups
+        .mockResolvedValueOnce(createMockProcess('no .last-sync file')); // cat .last-sync
+
+      const env = createMockEnvWithR2();
+
+      const result = await syncToR2(sandbox, env);
+
+      expect(result.success).toBe(false);
+      expect(result.error).toBe('Sync aborted: no config file found');
+      expect(result.details).toContain('Gateway running');
+      expect(result.details).toContain('proc_123');
+      expect(result.details).toContain('Local /root/.openclaw/');
+      expect(result.details).toContain('R2 backups');
     });
   });
 
diff --git a/src/gateway/sync.ts b/src/gateway/sync.ts
index 63808c471..119f19185 100644
--- a/src/gateway/sync.ts
+++ b/src/gateway/sync.ts
@@ -2,6 +2,7 @@ import type { Sandbox } from '@cloudflare/sandbox';
 import type { MoltbotEnv } from '../types';
 import { R2_MOUNT_PATH } from '../config';
 import { mountR2Storage } from './r2';
+import { findExistingMoltbotProcess } from './process';
 import { waitForProcess } from './utils';
 
 export interface SyncResult {
@@ -29,6 +30,69 @@ export interface SyncResult {
  * @param env - Worker environment bindings
  * @returns SyncResult with success status and optional error details
  */
+async function runDiagnosticCmd(sandbox: Sandbox, cmd: string): Promise<string> {
+  const proc = await sandbox.startProcess(cmd);
+  await waitForProcess(proc, 5000);
+  const logs = await proc.getLogs();
+  return (logs.stdout || '').trim();
+}
+
+async function diagnoseConfigMissing(sandbox: Sandbox): Promise<string> {
+  const parts: string[] = [];
+
+  // Check if the gateway process is running
+  const gateway = await findExistingMoltbotProcess(sandbox);
+  if (!gateway) {
+    parts.push('Gateway process is not running — config has not been created yet.');
+    return parts.join(' | ');
+  }
+
+  parts.push(`Gateway running (${gateway.id}, status: ${gateway.status})`);
+
+  // Get gateway logs for clues (did onboard or patching fail?)
+  try {
+    const logs = await gateway.getLogs();
+    const stderr = logs.stderr?.trim();
+    if (stderr) {
+      parts.push(`Gateway stderr: ${stderr.slice(0, 300)}`);
+    }
+  } catch {
+    // getLogs may not be available on all process types
+  }
+
+  // Check local config directory contents
+  try {
+    const localLs = await runDiagnosticCmd(sandbox, 'ls -la /root/.openclaw/ 2>&1');
+    parts.push(`Local /root/.openclaw/: ${localLs.slice(0, 300)}`);
+  } catch {
+    parts.push('Local /root/.openclaw/: failed to list');
+  }
+
+  // Check R2 backup directory contents
+  try {
+    const r2Ls = await runDiagnosticCmd(
+      sandbox,
+      `ls -la ${R2_MOUNT_PATH}/openclaw/ 2>&1; echo "---"; ls -la ${R2_MOUNT_PATH}/clawdbot/ 2>&1`,
+    );
+    parts.push(`R2 backups: ${r2Ls.slice(0, 300)}`);
+  } catch {
+    parts.push('R2 backups: failed to list');
+  }
+
+  // Check R2 mount health (can we actually read from it?)
+  try {
+    const mountTest = await runDiagnosticCmd(
+      sandbox,
+      `cat ${R2_MOUNT_PATH}/.last-sync 2>&1 || echo "no .last-sync file"`,
+    );
+    parts.push(`R2 .last-sync: ${mountTest.slice(0, 100)}`);
+  } catch {
+    parts.push('R2 mount: unresponsive');
+  }
+
+  return parts.join(' | ');
+}
+
 export async function syncToR2(sandbox: Sandbox, env: MoltbotEnv): Promise<SyncResult> {
   // Check if R2 is configured
   if (!env.R2_ACCESS_KEY_ID || !env.R2_SECRET_ACCESS_KEY || !env.CF_ACCOUNT_ID) {
@@ -54,10 +118,12 @@ export async function syncToR2(sandbox: Sandbox, env: MoltbotEnv): Promise<SyncR
       if (checkLegacy.exitCode === 0) {
         configDir = '/root/.clawdbot';
       } else {
+        // Gather diagnostics to explain why config is missing
+        const diagnostics = await diagnoseConfigMissing(sandbox);
         return {
           success: false,
           error: 'Sync aborted: no config file found',
-          details: 'Neither openclaw.json nor clawdbot.json found in config directory.',
+          details: diagnostics,
         };
       }
     }
diff --git a/src/routes/api.ts b/src/routes/api.ts
index bbc04feb7..f1af4d2b2 100644
--- a/src/routes/api.ts
+++ b/src/routes/api.ts
@@ -248,6 +248,18 @@ adminApi.get('/storage', async (c) => {
 adminApi.post('/storage/sync', async (c) => {
   const sandbox = c.get('sandbox');
 
+  // Check if the gateway is running before attempting sync
+  const gatewayProcess = await findExistingMoltbotProcess(sandbox);
+  if (!gatewayProcess) {
+    return c.json(
+      {
+        success: false,
+        error: 'Gateway not running yet, nothing to sync',
+      },
+      409,
+    );
+  }
+
   const result = await syncToR2(sandbox, c.env);
 
   if (result.success) {
@@ -257,7 +269,9 @@ adminApi.post('/storage/sync', async (c) => {
       lastSync: result.lastSync,
     });
   } else {
-    const status = result.error?.includes('not configured') ? 400 : 500;
+    const isClientError =
+      result.error?.includes('not configured') || result.error?.includes('Sync aborted');
+    const status = isClientError ? 400 : 500;
     return c.json(
       {
         success: false,