hermes-config/skills/software-development/web-ui-repair/references/nginx-server-block-diagnosis.md

Nginx Server Block Diagnosis: Served vs Edited Mismatch

Diagnostic Signal

You edit a file on disk, verify the edit is correct with grep or read_file, but the user reports the fix didn't work. Using curl -sk https://localhost/page.html | grep 'fix-pattern' returns empty — the fix is NOT in the served content.

Root Cause Pattern

Multiple nginx server blocks can serve the same domain on different ports. sites-available/ and sites-enabled/ may contain different files with different directives — not simply symlinks.

In this session:

• /etc/nginx/sites-available/shopproquote had listen 3448 ssl with aggressive caching (expires 30d; Cache-Control: public, immutable)
• /etc/nginx/sites-enabled/shopproquote had listen 443 ssl with NO caching headers and different location blocks
• The files were different regular files, not symlinks

Diagnosis Steps

# 1. Check what's actually enabled
ls -la /etc/nginx/sites-enabled/

# 2. Compare enabled vs available
diff /etc/nginx/sites-available/<name> /etc/nginx/sites-enabled/<name>

# 3. Check which port each server block listens on
grep -rn 'listen' /etc/nginx/sites-enabled/

# 4. Check the root directive
grep -rn 'root' /etc/nginx/sites-enabled/<name>

# 5. Check if any other enabled site uses the same port (conflict)
grep -rn 'listen.*PORT' /etc/nginx/sites-enabled/

# 6. Verify served content matches disk content
curl -sk https://localhost/page.html | grep -c 'your-fix-pattern'
# Should return ≥ 1. If 0, the file on disk isn't what's being served.

Common Scenarios

Symptom	Likely Cause
Curl shows fix, user doesn't see it	Browser cache
Curl doesn't show fix, disk has it	Wrong server block / root path
Curl shows OLD fix but not NEW one	File not saved, or nginx not reloaded
Port 443 vs port 3448 content differs	Two different server blocks, different root
JS loaded but HTML not updated	Static asset caching (see Browser Cache Busting)