Fix: Proxy body serialization and optional chaining syntax

server/index.js

@@ -320,6 +320,13 @@ app.use('/v1', requireAuth, createProxyMiddleware({
     // Add auth token for OpenClaw gateway
     proxyReq.setHeader('Authorization', `Bearer ${CONFIG.gatewayToken}`);
     proxyReq.setHeader('x-openclaw-agent-id', req.headers['x-openclaw-agent-id'] || 'main');
+    
+    // Re-serialize body if it was already parsed by express.json()
+    if (req.body && Object.keys(req.body).length > 0) {
+      const bodyData = JSON.stringify(req.body);
+      proxyReq.setHeader('Content-Length', Buffer.byteLength(bodyData));
+      proxyReq.write(bodyData);
+    }
   },
   onProxyRes: (proxyRes, req, res) => {
     // Handle SSE streaming