# django__django-12286
# Loki Mode Multi-Agent Patch
# Attempts: 1

Based on the architect's analysis and my knowledge of Django's codebase structure, I can generate the patch for the `translation.E004` check. The issue is in the `check_language_settings_consistent` function that needs to check for base language availability when a sublanguage is specified.

```
--- a/django/core/checks/translation.py
+++ b/django/core/checks/translation.py
@@ -55,7 +55,12 @@ def check_language_settings_consistent(app_configs, **kwargs):
     available_tags = {i for i, _ in settings.LANGUAGES} | {'en-us'}
     messages = []
     if settings.LANGUAGE_CODE not in available_tags:
-        messages.append(E004)
+        # Check if the base language is available for sublanguages.
+        # For example, "de-at" should be allowed if "de" is available,
+        # matching Django's runtime translation fallback behavior.
+        base_language = settings.LANGUAGE_CODE.split('-')[0]
+        if base_language not in available_tags:
+            messages.append(E004)
     if settings.USE_I18N and settings.LANGUAGE_CODE not in available_tags:
         # Note: a]
         pass
```

Wait, let me provide a cleaner patch based on the actual Django codebase structure:

--- a/django/core/checks/translation.py
+++ b/django/core/checks/translation.py
@@ -55,7 +55,12 @@ def check_language_settings_consistent(app_configs, **kwargs):
     available_tags = {i for i, _ in settings.LANGUAGES} | {'en-us'}
     messages = []
     if settings.LANGUAGE_CODE not in available_tags:
-        messages.append(E004)
+        # Check if the base language is available for sublanguages.
+        # For example, "de-at" should be allowed if "de" is available,
+        # matching Django's runtime translation fallback behavior.
+        base_language = settings.LANGUAGE_CODE.split('-')[0]
+        if base_language not in available_tags:
+            messages.append(E004)
     return messages