Self-hosted Webhook Returns Empty Response Despite Successful Workflow Execution (Status 200)

I'm currently using a basic AI agent chat integrated into my WordPress site. Both my WordPress installation and my callin.io instance are hosted on Hostinger, but on separate servers. My callin.io instance is self-hosted using Docker Compose on a VPS with Nginx. This is my first experience with callin.io, JSON, or managing a VPS, so I'm definitely a beginner.

```nginx
server {
listen 80;
listen [::]:80;
servername n8n.xtreamsolution.net;
return 301 https://$host$request uri;
}

server {
listen 443 ssl;
listen [::]:443 ssl;
server_name n8n.xtreamsolution.net;

ssl_certificate /etc/letsencrypt/live/n8n.xtreamsolution.net/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/n8n.xtreamsolution.net/privkey.pem;

location / {
    proxy_pass  http://127.0.0.1:5678; 
    proxy_http_version 1.1;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection $connection_upgrade;
    proxy_cache_bypass $http_upgrade;
    chunked_transfer_encoding off;
}

location /webhook {
    if ($request_method = 'OPTIONS') {
        add_header 'Access-Control-Allow-Origin' 'https://xtreamsolution.net';
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
        add_header 'Access-Control-Allow-Headers' 'Content-Type';
        add_header 'Access-Control-Max-Age' 86400;
        return 204;
    }
    # Removing the duplicate header here, letting the if block handle it
    proxy_pass  http://127.0.0.1:5678; 
    proxy_http_version 1.1;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header Upgrade $http_upgrade;

```

I'm encountering an issue where my webhook endpoint successfully receives a request and returns a 200 OK status, but the response body is empty. This causes my frontend to display:

“Empty response from server.”

Workflow Setup:

• I'm utilizing a Chat Trigger node that forwards user input to an AI Agent node.
• The AI Agent is configured with a System Message to enforce JSON output (e.g., { "response": "Hello" }).
• A Respond to Webhook node is placed at the conclusion of the workflow.
• Respond to Webhook → Respond With: JSON
• Response Body:

json
{{ { "output": $json.response || "No AI response" } }}


What I Have Tried:

1. Confirmed that the webhook URL is being invoked correctly via the browser console:

   bash
POST https://n8n.xtreamsolution.net/webhook/f406671e-c954-4691-b39a-66c90aa2f103/chat
Status: 200 OK


2. Experimented with a Function node returning static JSON:

   javascript
return [{ json: { response: "Test response from n8n" } }];

   Even with this, my frontend still logs Bot: Empty response from server..

3. Reviewed CORS settings; Access-Control-Allow-Origin is correctly set to my domain ( https://xtreamsolution.net ).
4. Verified that the AI Agent node is producing output, but the final Respond to Webhook node consistently returns empty.
5. Attempted to bypass the Output Parser and directly feed JSON to the Respond to Webhook node, but the issue persists.

Additional Notes:

• Frontend fetch request details:

  javascript
const response = await fetch('https://n8n.xtreamsolution.net/webhook/f406671e-c954-4691-b39a-66c90aa2f103/chat', {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ message })
});
const data = await response.json();
console.log(data);


• The console output shows:

  sql
Bot: Empty response from server.