Django Expert

Django Expert — AI Tutor Backend

Expert guidance for Django 5 work on this specific codebase. For general Django docs, don't replicate — assume the reader knows Django. This focuses on patterns that are PROJECT-SPECIFIC or commonly-missed.

The stack

• Django 5.x, Python 3.11
• PostgreSQL prod (Azure), SQLite dev
• Gunicorn 4 workers × 4 threads, 120s timeout
• WhiteNoise for static files
• ChromaDB (via apps/curriculum/knowledge_base.py) with sentence-transformers embeddings
• LLM abstraction: apps/llm/client.py::BaseLLMClient (Anthropic / OpenAI / Google / Ollama)
• No DRF yet (planned in memory/mobile_rn_plan.md Phase A — Django REST Framework + JWT + CORS + /api/v1/*)
• Azure Container Apps deploy via Pulumi (infra/) + GitHub Actions

Apps and what each owns

Critical patterns for this project

1. Multi-tenancy (institution scoping)

Every query touching user data must scope by institution. Missing this is a cross-school data leak.

Three institution states:

• institution=<inst> — scoped to one school
• institution=None — platform-wide / "All Schools" super-admin content
• In ChromaDB: None normalized to GLOBAL_INSTITUTION_ID = 0 (see apps/curriculum/knowledge_base.py:106)

Standard query pattern for student-facing views (include platform-wide content):

from django.db.models import Q

def get_visible_lessons(student):
    inst = student.memberships.filter(is_active=True).first().institution
    return Lesson.objects.filter(
        Q(unit__course__institution=inst) | Q(unit__course__institution__isnull=True),
        is_published=True,
    )

For admin/teacher queries, institution is usually narrower — scope to their institution only unless they're super-admin (user.is_staff).

2. The LLM client abstraction (apps/llm/client.py)

Never call Anthropic/OpenAI SDK directly. Always go through the abstraction:

from apps.llm.client import get_llm_client
from apps.llm.models import ModelConfig

config = ModelConfig.get_for(institution=inst, purpose='tutoring')
client = get_llm_client(config)
response = client.generate(
    messages=[{"role": "user", "content": "..."}],
    system_prompt="...",
    max_tokens=1024,
)
# response.content, response.tokens_in, response.tokens_out, response.model, response.stop_reason

ModelConfig.get_for(purpose=X) picks the right model per purpose: generation, tutoring, exit_tickets, skill_extraction, image_generation.

3. The ConversationalTutor engine

Core file: apps/tutoring/conversational_tutor.py. This is large (~4000+ lines) — don't try to read it all at once.

Key rules (also in CLAUDE.md):

• SessionState enum, not ConversationPhase. Values: TUTORING, EXIT_TICKET, COMPLETED. Display-level 5E phase comes from each LessonStep.phase.
• Media signal: tutor appends |||MEDIA:N||| as the LAST line (N = 1-based index into _media_id_map). Parse + strip BEFORE _save_turn().
• State persistence: engine state lives in TutorSession.engine_state (JSONField). Loaded via _load_state(), saved via _save_state().
• Public API: respond(student_input: str) -> TutorMessage, respond_stream(...) (exists but unused in prod — Azure Container Apps buffers).
• Step evaluation: _evaluate_step() uses instructor (structured LLM) returning StepEvaluationResult. _should_advance_step() applies safety valves (exchange cap, practice fast-path).
• Exit ticket trigger: current_topic_index >= len(self.steps) (no more steps). NOT by phase transition.

4. Content generator JSON robustness

LLMs sometimes return single-quoted Python dicts, not JSON. apps/curriculum/content_generator.py has defenses:

• _try_fix_json() — handles single-quote → double-quote, Python bool/None → JSON literals
• _generate_steps() — 3-attempt retry loop with correction prompt

Don't bypass these. If you see JSON-parsing errors, extend these defenses.

5. Logging in background threads

Background generation (dashboard/background_tasks.py, material_tasks.py) runs in threads, not Celery. logger.info() may not show in dev server. Use:

print(f"[ContentGen] Starting lesson {lesson_id}", flush=True)

The [ContentGen] prefix is the convention — grep-friendly.

6. Stuck content generation

Content generation can hang with content_status='generating'. Manual reset:

from apps.curriculum.models import Lesson
Lesson.objects.filter(content_status='generating').update(content_status='pending')

If you're writing new content-gen logic, always wrap in try/except + set failed or pending on exception.

7. Media files and MediaAsset

• MediaAsset FK to Institution (scoped)
• Files go to media/{institution.slug}/{filename}
• Served at /media/<path> — no auth gate (direct file serve via serve() in config/urls.py). OK for images/audio. Don't put sensitive data there.
• LessonStep.media (JSONField) references these via URL strings: {"images": [{"url": ..., "alt": ...}], ...}

8. Azure Container Apps gotchas

See CLAUDE.md for the full list. Key ones when writing code:

• No SSE — use JsonResponse, not StreamingHttpResponse
• ChromaDB on /tmp — VECTORDB_ROOT=/tmp/vectordb, Dockerfile copies from SMB mount at startup
• Images must be amd64 — your Mac builds arm64 by default. Use GitHub Actions for deploys, or --platform linux/amd64 locally.
• CSRF_TRUSTED_ORIGINS uses env.default_domain in Pulumi (not hardcoded)

Migration patterns

Safe migrations

• One logical change per migration file
• Descriptive names: 0014_add_session_participant.py
• Data migrations: use RunPython with forward + reverse function
• Backfill migrations: dry-run against a prod DB dump FIRST
• Column removal: split across two releases — stop writing to column (release N), drop column (release N+1)

Dry-run checklist

# Before running in prod:
python manage.py makemigrations --dry-run
python manage.py migrate --plan  # see SQL to be run
python manage.py sqlmigrate <app_name> <migration_number>  # inspect SQL

DRF patterns (once installed)

The RN plan (memory/mobile_rn_plan.md) adds DRF. When you're building those endpoints, default pattern:

# apps/api/views/lessons.py
from rest_framework.views import APIView
from rest_framework.permissions import IsAuthenticated
from apps.api.permissions import IsInstitutionMember
from apps.api.mixins import InstitutionScopedMixin

class LessonListView(InstitutionScopedMixin, APIView):
    permission_classes = [IsAuthenticated, IsInstitutionMember]

    def get(self, request):
        qs = self.scope_to_institution(Lesson.objects.all())  # enforces scoping
        serializer = LessonSerializer(qs, many=True)
        return Response(serializer.data)

The InstitutionScopedMixin should be the default — every mobile view uses it.

Auth: JWT via simplejwt, SessionAuthentication kept for web parity. Dual-auth in DEFAULT_AUTHENTICATION_CLASSES.

OpenAPI: use drf-spectacular — auto-generates schema for mobile TS type generation.

Testing patterns

# apps/tutoring/tests/test_foo.py
import pytest
from django.contrib.auth.models import User
from apps.tutoring.tutoring_models import TutorSession

@pytest.mark.django_db
def test_something(student_user, published_lesson):
    # Use factories where they exist (apps/*/tests/factories.py)
    session = TutorSession.objects.create(
        student=student_user,
        lesson=published_lesson,
        institution=student_user.memberships.first().institution,
    )
    assert session.status == 'active'

Run scoped tests: pytest apps/tutoring/tests/ -k mastery -v.

Before making risky changes

Before editing config/settings.py: check if the variable is referenced in infra/__main__.py or Dockerfile. Settings changes can silently break production.

Before a migration: run python manage.py makemigrations --dry-run first. Unnecessary migrations (from model docstring changes, etc.) bloat history.

Before deleting a field: grep the whole project for the field name. Dead fields often have template references that break silently.

Before changing conversational_tutor.py: read the relevant method + its callers. State is shared via self. attributes persisted in engine_state. Adding a new attribute requires updating _save_state() and _load_state().

Resources to read when needed

• CLAUDE.md — always-apply project rules
• memory/lesson_competency_plan.md — the mastery/exit-ticket work in progress
• memory/mobile_rn_plan.md — upcoming DRF + JWT + mobile API layer
• README.md — architecture overview (780 lines, deliberate — don't edit casually)
• Auto-memory at ~/.claude/projects/-Users-edwardamoah-Documents-GitHub-ai-tutor/memory/ — deployment history, past incidents

Source: eai6/ai-tutor — distributed by TomeVault.