Custom Nginx config not applied at container startup until a Proxy Host is edited and saved

Checklist

• Have you pulled and found the error with jc21/nginx-proxy-manager:latest docker image?
  • Yes
• Are you sure you're not using someone else's docker image?
  • Yes
• Have you searched for similar issues (both open and closed)?
  • Yes

Describe the bug
When using a valid custom Nginx configuration file, it is not loaded on container startup as expected.

I have added the following line in the file /data/nginx/custom/server_proxy.conf:

real_ip_header CF-Connecting-IP;

This directive is never applied when the container is started. I can confirm this by looking at the logs and inspecting the X-Real-IP header — it always contains Cloudflare’s IP.

However, as soon as I open any existing proxy host in the UI, click Edit, and then click Save (without changing anything), the configuration is reloaded and immediately works as expected. X-Real-IP then contains the real IP address of the client.

This looks like a bug where custom snippets are not loaded or not properly injected until a proxy host is re-saved.

Nginx Proxy Manager Version
v2.12.3

To Reproduce
Steps to reproduce the behavior:

1. Create a file /data/nginx/custom/server_proxy.conf with content:

   real_ip_header CF-Connecting-IP;
   

2. Start the container normally

3. Make a request to any proxy host (e.g. via curl) and observe the value of the X-Real-IP header → it's the Cloudflare IP

4. Go to the UI, open any existing proxy host, click Edit, then click Save

5. Retry the request → X-Real-IP now contains the real client IP

Expected behavior
The configuration snippet /data/nginx/custom/server_proxy.conf should be taken into account immediately after starting the container, without requiring a manual Edit+Save in the UI.

Operating System
Ubuntu 24.04 LTS running Docker 24.0+ and Docker Compose v2.24.4

Start with container startup handling for /data/nginx/custom/server_proxy.conf, then compare it with the configuration reload path triggered by editing and saving a proxy host in the UI. Reproduce the issue with the provided real_ip_header directive and confirm that a fresh container applies it immediately without requiring an Edit and Save.