# Jinja2 Template Inheritance Debugging

## Silent Block Omission

**Symptom**: Child template's `{% block X %}` content is completely absent from rendered page. No error, no warning.

**Root cause**: Parent template (base.html) does NOT define `{% block X %}{% endblock %}`. Jinja2 silently ignores child blocks that don't have a corresponding parent block definition.

**Detection**:
```bash
# Check if parent template defines the block
grep -n "block_name" templates/base.html

# Check rendered output for the expected content
curl -s https://site/page | grep -o "expected_js_variable"
```

**Example from ephron.ren**:
- `blog/templates/admin/collection_edit.html` defined `{% block extra_scripts %}` with critical JavaScript
- `blog/templates/base.html` had `{% block extra_styles %}` and `{% block content %}` but NO `{% block extra_scripts %}`
- Result: All JavaScript for article selection was silently omitted from the page
- Other services (prompt, auth, canvas, home) all had `extra_scripts` defined in their base templates

**Fix**: Add the missing block definition to the parent template:
```html
<!-- Before </body> -->
{% block extra_scripts %}{% endblock %}
```

**Prevention**: When creating child templates, verify the parent template defines all blocks you intend to override. Use `grep` to check.

**Cross-service consistency check**: When debugging template issues in multi-service sites, compare the base templates across all services to find missing block definitions:
```bash
for svc in blog auth canvas prompt home; do
  echo "=== $svc ==="
  grep -n "block.*endblock\|{% block" $svc/templates/base.html 2>/dev/null || \
  grep -n "block.*endblock\|{% block" $svc/templates/_design_system/page_shell.html 2>/dev/null
done
```