diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..eb5ed6f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,34 @@
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+*.egg
+*.egg-info/
+dist/
+build/
+.eggs/
+
+# Virtual environments
+.venv/
+venv/
+ENV/
+
+# Django
+db.sqlite3
+db.sqlite3-journal
+staticfiles/
+*.log
+local_settings.py
+
+# macOS
+.DS_Store
+
+# IDEs
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# Data migration artefacts (generated, not committed)
+legacy_export.json
diff --git a/COMPLETION.md b/COMPLETION.md
new file mode 100644
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--- /dev/null
+++ b/COMPLETION.md
@@ -0,0 +1,321 @@
+# Phase 0: Scaffolding — COMPLETION
+
+**Agent:** Phase 0 Scaffolding  
+**Branch:** `modernize/django5`  
+**Date:** 2026-06-13
+
+---
+
+## What Was Created
+
+### New project structure
+
+```
+pythonfiddle_modern/       ← new Django 5.2 project package
+  __init__.py
+  settings.py              ← fully configured (see below)
+  urls.py                  ← minimal (admin only; URLs agent adds the rest)
+  wsgi.py
+  asgi.py
+manage.py                  ← replaced with Django 5.2 version
+requirements.txt           ← updated with modern deps
+.gitignore                 ← added
+docs/modernization/
+  PORTED_MODELS.md         ← full model field documentation
+  DATA_MIGRATION.md        ← placeholder + export/import pseudocode
+  VALIDATION_CHECKLIST.md  ← placeholder for validation agent
+  old_inspectdb.txt        ← "No existing DB found" (no legacy DB in repo)
+COMPLETION.md              ← this file
+```
+
+### Files left intact (legacy reference, READ ONLY)
+
+```
+__init__.py           ← legacy root package marker
+context_processors.py ← legacy (not wired into new settings)
+files.py              ← legacy static file lists (mediasync)
+settings.default.py   ← legacy Django 1.4 settings (reference only)
+urls.py               ← legacy root urlconf (reference only)
+locale/               ← existing translation files (reusable)
+templates/            ← existing templates (starting point for URLs agent)
+```
+
+---
+
+## Bootstrap Commands
+
+```bash
+# Activate the virtual environment
+source /Users/yuguang/Projects/pythonfiddle-modernize/.venv/bin/activate
+
+# Install cloud_ide from source (editable)
+pip install -e /Users/yuguang/Projects/django-cloud-ide
+
+# Run migrations
+python manage.py migrate
+
+# Start development server
+python manage.py runserver 8001
+```
+
+The `DJANGO_SETTINGS_MODULE` is pre-configured in `manage.py` as `pythonfiddle_modern.settings`.
+
+---
+
+## cloud_ide Package Install Status
+
+- **Installed:** Yes, editable install from `/Users/yuguang/Projects/django-cloud-ide`
+- **Version:** 1.2.0
+- **Python version:** 3.14.3
+- **Django version:** 5.2.15
+
+### Python 2 → Python 3 / Django 1.4 → Django 5.2 patches applied to cloud_ide
+
+All patches were applied directly to the source at `/Users/yuguang/Projects/django-cloud-ide`:
+
+| File | Change |
+|------|--------|
+| `cloud_ide/fiddle/compression.py` | Rewrote for Python 3: `cStringIO→io`, added local `compress_string`, fixed exception syntax, fixed `db_type()` to use `connection.settings_dict` |
+| `cloud_ide/fiddle/models.py` | Absolute imports; `ugettext_lazy→gettext_lazy`; `@permalink→reverse()`; added `on_delete` to both ForeignKeys; `__unicode__→__str__` |
+| `cloud_ide/fiddle/forms.py` | Fixed implicit relative import `from models import *` |
+| `cloud_ide/fiddle/admin.py` | Fixed implicit relative import |
+| `cloud_ide/fiddle/views.py` | `render_to_response+RequestContext→render`; `simplejson→json`; `is_authenticated()→.is_authenticated`; `is_ajax()→headers check`; `mimetype→content_type`; absolute imports |
+| `cloud_ide/fiddle/jsonresponse.py` | Rewrote to extend Django's built-in `JsonResponse` |
+| `cloud_ide/fiddle/templatetags/jqtmpl.py` | `TOKEN_BLOCK/TOKEN_VAR→TokenType.BLOCK/VAR`; `TextNode` from `django.template.base` |
+
+**Note:** `cloud_ide/fiddle/migrations/0001_initial.py` was auto-generated by `makemigrations` and lives in the cloud_ide source tree.
+
+---
+
+## Key Models Found in django-cloud-ide
+
+See `docs/modernization/PORTED_MODELS.md` for full details.
+
+**`Language`** (fiddle_language)
+- `id` PK, `name` CharField(30)
+
+**`Snippet`** (fiddle_snippet)
+- `id`, `title`(80), `slug`(100), `author` FK→User, `description`(300)
+- `tags` TaggableManager, `last_modified` auto_now, `code` CompressedTextField, `language` FK→Language
+
+**`CompressedTextField`**: custom TextField that gzip-compresses code blobs in the DB.
+
+---
+
+## Installed Apps (settings.py)
+
+```python
+INSTALLED_APPS = [
+    'whitenoise.runserver_nostatic',
+    'django.contrib.admin',
+    'django.contrib.auth',
+    'django.contrib.contenttypes',
+    'django.contrib.sessions',
+    'django.contrib.messages',
+    'django.contrib.staticfiles',
+    'django.contrib.sites',
+    'django.contrib.sitemaps',
+    'social_django',
+    'taggit',
+    'cloud_ide.fiddle',
+]
+```
+
+---
+
+## Exit Criteria — PASSED
+
+- [x] `python manage.py migrate` exits 0 (all migrations applied including `fiddle.0001_initial`)
+- [x] `python manage.py runserver 8001` starts without ImportError on Django 5.2.15
+
+---
+
+---
+
+## Phase 3: Static Assets — COMPLETE
+
+**Agent:** Phase 3 Static Assets  
+**Date:** 2026-06-13
+
+### Changes Made
+
+| File | Change |
+|------|--------|
+| `pythonfiddle_modern/settings.py` | Added `STATICFILES_DIRS = [BASE_DIR / 'static']` |
+| `static/favicon.ico` | Created minimal 16×16 transparent ICO placeholder |
+
+### What Was Already in Place (from Phase 0)
+
+- `STATIC_ROOT = BASE_DIR / 'staticfiles'` ✓
+- Whitenoise `CompressedManifestStaticFilesStorage` in `STORAGES` ✓
+- `WhiteNoiseMiddleware` in `MIDDLEWARE` (after `SecurityMiddleware`) ✓
+- `whitenoise.runserver_nostatic` in `INSTALLED_APPS` ✓
+- `staticfiles/` in `.gitignore` ✓
+- No MEDIASYNC or AWS_* settings present ✓
+
+### Verification Results
+
+```
+python manage.py collectstatic --noinput
+→ 128 static files copied to staticfiles/, 384 post-processed
+
+python manage.py check
+→ System check identified no issues (0 silenced)
+```
+
+### Exit Criteria — PASSED
+
+- [x] `collectstatic` completes without errors
+- [x] `manage.py check` reports 0 issues
+- [x] `staticfiles/` excluded from version control via `.gitignore`
+- [x] No legacy mediasync/AWS settings in codebase
+- [x] Committed and pushed to `modernize/django5`
+
+---
+
+## Open Questions / Handoff Notes
+
+1. **cloud_ide.login** app is not in INSTALLED_APPS. It still imports from the old `social_auth` package. The Auth agent (Phase 2) must either patch it to use `social_django` or replace it entirely.
+2. **cloud_ide.shared** and **cloud_ide.snippet** are not in INSTALLED_APPS. The URLs agent (Phase 5) should evaluate whether these are needed.
+3. **CLOUD_IDE_TEMPLATES_DIR** is hardcoded to `/Users/yuguang/Projects/cloud-ide-templates`. Move to an env variable before production deployment.
+4. **No legacy DB** was found at the legacy project path. If a production DB dump is available, the Data agent should run `inspectdb` against it and update `old_inspectdb.txt`.
+5. **django-chunks** was removed. If any templates reference `{% load chunks %}`, those must be updated.
+6. **Social auth credentials** are blank in settings.py. The Auth agent must wire up the OAuth keys (via env vars).
+7. **Snippet.slug** has no `unique=True` constraint — the Models agent should evaluate adding it.
+
+---
+
+## Phase 1: Models + Data
+
+**Agent:** Phase 1 Models + Data
+**Branch:** `modernize/django5` (commit `a77f3e8`)
+**Date:** 2026-06-14
+
+### What Was Done
+
+#### Scripts created
+
+| File | Purpose |
+|---|---|
+| `scripts/export_legacy_data.py` | Reads legacy SQLite DB (no Django needed), dumps Language/Snippet/taggit to JSON, decompresses gzip blobs |
+| `scripts/import_legacy_data.py` | Reads JSON export, `get_or_create` Language, `create` Snippet with author fallback, re-applies tags |
+| `scripts/README.md` | Full usage docs + roundtrip example |
+| `scripts/__init__.py` | Package marker |
+
+#### Documentation updated
+
+- `docs/modernization/DATA_MIGRATION.md` — filled in with actual commands, column-level schema mapping, roundtrip test results, and open issues.
+
+#### Bug fix: `CompressedTextField.get_db_prep_save` (Python 3)
+
+The `get_db_prep_save` method was calling `models.TextField.get_db_prep_save`, which in Python 3 applies `str()` to the compressed bytes — storing `b'\x1f\x8b...'` as TEXT instead of a binary BLOB. Fixed by returning the compressed bytes directly, bypassing TextField's string conversion. Committed to `django-cloud-ide` @ `eb5843d` and pushed to `origin/master`.
+
+### Roundtrip Test — PASSED
+
+```
+Export:  Languages: 1  Snippets: 1
+Import:  Snippets created: 1  Snippets skipped: 0
+Verify:  code='print("hello")'  tags=['python','test']  author='testuser'  ✓
+```
+
+### Open Questions / Handoff Notes
+
+1. **No legacy production DB** was available to test against real data. The roundtrip was validated on a freshly-seeded test DB.
+2. **`last_modified` not preserved** — `auto_now=True` resets timestamps on import. Use raw SQL `UPDATE` if original timestamps matter.
+3. **`Snippet.slug` uniqueness** — still no `unique=True`. Evaluate before launch to prevent URL collisions.
+4. **Placeholder user** (`legacy_import_user`) is auto-created for orphaned snippets. Reassign via Django admin after user migration.
+5. **`auth_user` / social auth not migrated** — users must re-authenticate after launch.
+
+---
+
+## Phase 2: Auth — COMPLETE
+
+**Agent:** Phase 2 Auth  
+**Branch:** `modernize/django5`  
+**Date:** 2026-06-13
+
+### What Was Done
+
+#### Settings (`pythonfiddle_modern/settings.py`)
+
+| Change | Detail |
+|--------|---------|
+| `import os` | Added at top of file |
+| `SOCIAL_AUTH_URL_NAMESPACE = 'social'` | Must match `namespace=` in `urls.py` |
+| OAuth keys via `os.environ.get()` | `GOOGLE_KEY/SECRET`, `TWITTER_KEY/SECRET`, `FACEBOOK_KEY/SECRET` |
+
+Settings already in place from Phase 0 (no changes needed):
+- `social_django` in `INSTALLED_APPS` ✓
+- `AUTHENTICATION_BACKENDS` with Google/Twitter/Facebook + ModelBackend ✓
+- `social_django.context_processors.backends` and `.login_redirect` ✓
+- `LOGIN_URL = '/login/'`, `LOGIN_REDIRECT_URL = '/'`, `LOGOUT_REDIRECT_URL = '/'` ✓
+
+#### URLs (`pythonfiddle_modern/urls.py`)
+
+- `path('social-auth/', include('social_django.urls', namespace='social'))` — all OAuth endpoints
+- `path('login/', TemplateView.as_view(template_name='login.html'), name='login')` — login page placeholder (Phase 5 will supply the real template)
+- `path('logout/', LogoutView.as_view(next_page='/'), name='logout')` — POST-only logout (Django 5 CSRF-safe)
+
+**Note:** Mounted `social_django.urls` only once. Mounting it twice under the same namespace causes `ImproperlyConfigured` in Django 5.
+
+#### cloud_ide.login status — SUPERSEDED (do not add to INSTALLED_APPS)
+
+`/Users/yuguang/Projects/django-cloud-ide/cloud_ide/login/` is legacy Django 1.4 code:
+- `models.py` imports from `social_auth.signals` and `social_auth.backends.facebook` (package removed)
+- `urls.py` uses `from django.conf.urls.defaults import patterns` (removed in Django 2)
+- `views.py` uses `render_to_response` + `RequestContext` (removed in Django 5) and `is_authenticated()` as a method call (fixed upstream in Phase 0)
+
+**Decision:** Do not add `cloud_ide.login` to `INSTALLED_APPS`. `social_django` provides all necessary OAuth login/callback/disconnect views. The `/login/` page (Phase 5) will render provider links using `{% url 'social:begin' 'google-oauth2' %}` etc.
+
+If the `CustomUser` model from `cloud_ide/login/models.py` is needed, port it as a separate `accounts` app that uses `AbstractUser` — but for now the standard `auth.User` is sufficient.
+
+### Verification
+
+```
+python manage.py check
+→ System check identified no issues (0 silenced)
+
+python manage.py migrate
+→ No migrations to apply  (social_django migrations were already applied in Phase 0)
+
+reverse('social:begin', kwargs={'backend': 'google-oauth2'})  → /social-auth/login/google-oauth2/
+reverse('social:complete', kwargs={'backend': 'google-oauth2'})  → /social-auth/complete/google-oauth2/
+reverse('social:begin', kwargs={'backend': 'twitter'})  → /social-auth/login/twitter/
+reverse('login')  → /login/
+reverse('logout')  → /logout/
+```
+
+### Exit Criteria — PASSED
+
+- [x] `social_django` in `INSTALLED_APPS`, migrations applied
+- [x] `AUTHENTICATION_BACKENDS` lists Google OAuth2, Twitter OAuth, Facebook OAuth2
+- [x] `SOCIAL_AUTH_URL_NAMESPACE = 'social'` matches URL namespace
+- [x] OAuth keys wired to environment variables
+- [x] `manage.py check` reports 0 issues
+- [x] URL reverse for all social backends works
+- [x] `cloud_ide.login` legacy status documented — superseded by `social_django`
+- [x] Committed and pushed to `modernize/django5`
+
+### Open Steps — Manual OAuth Credential Setup
+
+Before social login can be tested end-to-end, developers must:
+
+1. **Google OAuth2** — Create a project in [Google Cloud Console](https://console.cloud.google.com/), enable the People API, create OAuth 2.0 credentials, and set the authorized redirect URI to `https://<your-domain>/social-auth/complete/google-oauth2/`. Then set:
+   ```
+   export GOOGLE_KEY=<client-id>
+   export GOOGLE_SECRET=<client-secret>
+   ```
+
+2. **Twitter/X OAuth** — Create an app at [developer.twitter.com](https://developer.twitter.com/), enable "Sign in with Twitter", set callback URL to `https://<your-domain>/social-auth/complete/twitter/`. Then set:
+   ```
+   export TWITTER_KEY=<api-key>
+   export TWITTER_SECRET=<api-secret>
+   ```
+
+3. **Facebook OAuth2** — Create an app at [developers.facebook.com](https://developers.facebook.com/), add Facebook Login product, set redirect URI to `https://<your-domain>/social-auth/complete/facebook/`. Then set:
+   ```
+   export FACEBOOK_KEY=<app-id>
+   export FACEBOOK_SECRET=<app-secret>
+   ```
+
+4. For local development use `http://127.0.0.1:8001` as the domain and register it in each provider's allowed origins.
diff --git a/docs/modernization/DATA_MIGRATION.md b/docs/modernization/DATA_MIGRATION.md
new file mode 100644
index 0000000..b27a6d5
--- /dev/null
+++ b/docs/modernization/DATA_MIGRATION.md
@@ -0,0 +1,131 @@
+# Data Migration
+
+**Status:** Complete — scripts written and roundtrip-tested by Phase 1 (Models + Data) agent.
+
+---
+
+## Overview
+
+The data migration strategy uses standalone export/import scripts rather than Django
+migration history. The legacy Django 1.4 project stores data in SQLite (file: `fiddle`,
+no extension, in the legacy project root).
+
+Scripts live in `scripts/`. See `scripts/README.md` for full usage documentation.
+
+---
+
+## Legacy → Modern Schema Mapping
+
+| Legacy table | Legacy column | New model field | Notes |
+|---|---|---|---|
+| `fiddle_language` | `id` | `Language.id` | PK preserved via `get_or_create` |
+| `fiddle_language` | `name` | `Language.name` | Used as lookup key |
+| `fiddle_snippet` | `id` | _(not preserved)_ | New auto-incremented PK assigned |
+| `fiddle_snippet` | `title` | `Snippet.title` | Direct copy |
+| `fiddle_snippet` | `slug` | `Snippet.slug` | Re-generated from title on `save()` |
+| `fiddle_snippet` | `author_id` | `Snippet.author` | Looked up by username; falls back to `legacy_import_user` |
+| `fiddle_snippet` | `description` | `Snippet.description` | Direct copy; empty string if NULL |
+| `fiddle_snippet` | `last_modified` | `Snippet.last_modified` | **Not preserved** — `auto_now=True` sets it to import time |
+| `fiddle_snippet` | `code` | `Snippet.code` | gzip-decompressed by export script; re-compressed by ORM on import |
+| `fiddle_snippet` | `language_id` | `Snippet.language` | Re-linked via `lang_map` (legacy id → new Language object) |
+| `taggit_tag` + `taggit_taggeditem` | — | `Snippet.tags` | Re-applied via `snippet.tags.set(tags)` |
+| `auth_user` | `username` | Used for author lookup only | Passwords / social auth **not migrated** |
+
+### Tables NOT migrated
+
+| Table | Reason |
+|---|---|
+| `auth_user` | Passwords are Django-hashed; social auth must be re-linked by users |
+| `social_auth_usersocialauth` | OAuth tokens are short-lived; users re-authenticate after launch |
+| `django_chunks` | Removed in modernization; templates updated to not use `{% load chunks %}` |
+
+---
+
+## Step-by-step Migration Commands
+
+```bash
+# 0. Activate the virtualenv
+cd /Users/yuguang/Projects/pythonfiddle-modernize
+source .venv/bin/activate
+
+# 1. Ensure the modern DB is fully migrated
+python manage.py migrate
+
+# 2. Export from the legacy SQLite DB
+#    (legacy DB has no .sqlite extension)
+python scripts/export_legacy_data.py ../pythonfiddle/fiddle legacy_export.json
+
+# 3. Verify the export
+python -c "
+import json
+d = json.load(open('legacy_export.json'))
+print('Languages:', len(d['languages']), '| Snippets:', len(d['snippets']))
+"
+
+# 4. Import into the modern DB
+python scripts/import_legacy_data.py legacy_export.json
+
+# 5. Verify the import
+python manage.py shell -c "
+from cloud_ide.fiddle.models import Snippet, Language
+print('Languages:', Language.objects.count())
+print('Snippets:', Snippet.objects.count())
+"
+```
+
+---
+
+## Roundtrip Test (Phase 1 Validation)
+
+The following was run successfully against a fresh `db.sqlite3`:
+
+```bash
+# Create test data
+python manage.py shell -c "
+from cloud_ide.fiddle.models import Language, Snippet
+from django.contrib.auth.models import User
+u, _ = User.objects.get_or_create(username='testuser')
+lang, _ = Language.objects.get_or_create(name='Python')
+s = Snippet.objects.create(title='Hello', author=u, language=lang, code='print(\"hello\")')
+s.tags.add('test', 'python')
+print('Created:', s.id, s.title)
+"
+python scripts/export_legacy_data.py db.sqlite3 legacy_export.json
+python -c "import json; d=json.load(open('legacy_export.json')); print('Languages:', len(d['languages']), 'Snippets:', len(d['snippets']))"
+# → Languages: 1 Snippets: 1  ✓
+```
+
+Reimport verification (wipe + import):
+```bash
+python manage.py shell -c "from cloud_ide.fiddle.models import Snippet, Language; Snippet.objects.all().delete(); Language.objects.all().delete()"
+python scripts/import_legacy_data.py legacy_export.json
+# → Snippets created: 1, Snippets skipped: 0  ✓
+# code, tags, author, language all preserved  ✓
+```
+
+---
+
+## CompressedTextField Notes
+
+The `code` field uses `CompressedTextField` (`cloud_ide/fiddle/compression.py`) which
+gzip-compresses text before storing it as a SQLite `BLOB`.
+
+**Bug fixed in Phase 1:** `get_db_prep_save` was calling `models.TextField.get_db_prep_save`,
+which in Python 3 applies `str()` to compressed bytes — storing the repr `b'\x1f\x8b...'`
+as TEXT instead of binary. Fixed to return compressed bytes directly.
+
+The export script handles three cases for legacy `code` blobs:
+1. **gzip bytes** (standard) — decompressed normally
+2. **zlib bytes** (rare legacy variant) — `zlib.decompress` fallback
+3. **plain text bytes** (uncompressed rows) — decoded as UTF-8
+
+---
+
+## Open Issues
+
+- `last_modified` timestamps are **not preserved** (`auto_now=True`). Use a raw SQL
+  `UPDATE fiddle_snippet SET last_modified = ?` after import if originals are needed.
+- `Snippet.slug` has no `unique=True` constraint. Snippets with identical titles get
+  the same slug. Evaluate adding uniqueness before launch.
+- The placeholder user `legacy_import_user` is created for orphaned snippets.
+  Reassign via the Django admin after migrating user accounts.
diff --git a/docs/modernization/PORTED_MODELS.md b/docs/modernization/PORTED_MODELS.md
new file mode 100644
index 0000000..b6783e0
--- /dev/null
+++ b/docs/modernization/PORTED_MODELS.md
@@ -0,0 +1,97 @@
+# Ported Models
+
+Documented by Phase 0 (Scaffolding) agent.  
+Source: `/Users/yuguang/Projects/django-cloud-ide/cloud_ide/fiddle/models.py`
+
+---
+
+## Package: `cloud_ide.fiddle`
+
+### `Language`
+
+| Field | Type | Notes |
+|-------|------|-------|
+| `id` | AutoField (implicit) | PK |
+| `name` | CharField(max_length=30) | Language slug (e.g. "python", "javascript") |
+
+**Methods:**
+- `get_absolute_url()` → reverse `fiddle_language_detail`
+- `__str__()` → `self.name`
+
+---
+
+### `Snippet`
+
+| Field | Type | Notes |
+|-------|------|-------|
+| `id` | AutoField (implicit) | PK |
+| `title` | CharField(max_length=80) | Translated label: "Title" |
+| `slug` | SlugField(max_length=100) | Auto-generated from title on save |
+| `author` | ForeignKey(User, CASCADE) | Django auth User |
+| `description` | CharField(max_length=300) | Translated label: "Description" |
+| `tags` | TaggableManager | via django-taggit |
+| `last_modified` | DateTimeField(auto_now=True) | Updated on every save |
+| `code` | CompressedTextField | gzip-compressed text field (blob in DB) |
+| `language` | ForeignKey(Language, PROTECT) | Can't delete a Language with associated Snippets |
+
+**Meta:**
+- `ordering = ('-last_modified',)` — newest first
+
+**Methods:**
+- `save()` — auto-slugifies title
+- `get_tagstring()` — comma-separated tag names
+- `get_absolute_url()` — `/{language}/{slug}/` (multi-language) or `/{slug}/` (single)
+- `__str__()` → `self.title`
+
+**Manager: `SnippetManager`**
+- `top_authors()` — Users annotated with snippet count, ordered by score
+- `top_tags()` — most common tags
+- `matches_tag(tag)` — filter by tag
+
+---
+
+## `CompressedTextField`
+
+Custom `TextField` subclass in `cloud_ide/fiddle/compression.py`.
+
+- Stores text as gzip-compressed bytes (`blob` type in SQLite, `longblob` in MySQL)
+- Transparently compresses on `get_db_prep_save`
+- Decompresses on `post_init` signal
+
+**Django 5 changes applied:**
+- Removed Python 2 `cStringIO` → `io.BytesIO`
+- Removed `django.utils.text.compress_string` (dropped in Django 2.0) → local `compress_string` using `gzip`
+- Fixed Python 2 `raise Exception, msg` syntax → `raise Exception(msg)`
+
+---
+
+## Module-level constants (in `models.py`)
+
+These are template context defaults also defined in `models.py`:
+
+- `defaultFiddle` — `{'newFiddle': True, 'isOwner': True}`
+- `defaultMeta` — SEO defaults (title, description, keywords)
+- `languageMeta` — per-language SEO metadata dict (python, coffeescript, typescript, jsx, js, sass, scss, less, css, html, haml, jade, etc.)
+
+---
+
+## Python 2 → Python 3 / Django 1.4 → Django 5.2 Changes
+
+| File | Change |
+|------|--------|
+| `compression.py` | `cStringIO` → `io`; removed `django.utils.text.compress_string`; fixed exception syntax |
+| `models.py` | `from compression import` → `from cloud_ide.fiddle.compression import`; `ugettext_lazy` → `gettext_lazy`; `@permalink` → `reverse()`; added `on_delete` to ForeignKeys; `__unicode__` → `__str__` |
+| `forms.py` | `from models import *` → `from cloud_ide.fiddle.models import Snippet` |
+| `admin.py` | `from models import Snippet` → `from cloud_ide.fiddle.models import Snippet` |
+| `views.py` | `render_to_response`+`RequestContext` → `render`; `is_authenticated()` → `.is_authenticated`; `is_ajax()` → header check; `simplejson` → stdlib `json`; `mimetype` → `content_type` |
+| `jsonresponse.py` | `simplejson` → Django's `JsonResponse` |
+| `templatetags/jqtmpl.py` | `TOKEN_BLOCK`/`TOKEN_VAR` → `TokenType.BLOCK`/`TokenType.VAR`; `TextNode` from `django.template.base` |
+
+---
+
+## Open Questions for Models Agent (Phase 1)
+
+1. **CompressedTextField migration**: The initial migration stores `code` as `BlobField` (`blob` in SQLite). Existing data from the legacy DB may be gzip-compressed bytes or plain text. The export script must handle both.
+2. **Language seeding**: There is no fixture for `Language` records. The models agent should create initial data for common languages (python, javascript, etc.).
+3. **Snippet.slug uniqueness**: The current model has no `unique=True` on `slug`. Two snippets with the same title would get the same slug. Consider adding `unique=True` or making it `unique_for_date`.
+4. **Snippet.author nullable**: Currently `author` is non-nullable. For imported snippets whose author account doesn't exist in the new DB, a fallback user or null author is needed.
diff --git a/docs/modernization/VALIDATION_CHECKLIST.md b/docs/modernization/VALIDATION_CHECKLIST.md
new file mode 100644
index 0000000..da09b2f
--- /dev/null
+++ b/docs/modernization/VALIDATION_CHECKLIST.md
@@ -0,0 +1,43 @@
+# Validation Checklist
+
+**Status:** Placeholder — to be filled by Phase 6 (Validation) agent.
+
+---
+
+## Smoke Tests
+
+| Test | Expected | Status |
+|------|----------|--------|
+| `python manage.py migrate` | Exits 0, all migrations applied | [ ] |
+| `python manage.py runserver` starts | No ImportError, "Starting development server" | [ ] |
+| Home page (`/`) loads | HTTP 200 | [ ] |
+| New fiddle page loads | HTTP 200, editor visible | [ ] |
+| Save fiddle (POST `/save/`) | Returns JSON `{success: true}` | [ ] |
+| Open existing fiddle | HTTP 200, code populated | [ ] |
+| Login page (`/login/`) | HTTP 200 | [ ] |
+| Google OAuth redirect | Redirects to Google | [ ] |
+| Twitter OAuth redirect | Redirects to Twitter | [ ] |
+| Facebook OAuth redirect | Redirects to Facebook | [ ] |
+| Language switch (en ↔ zh) | UI text changes language | [ ] |
+| Admin (`/admin/`) | HTTP 200, login works | [ ] |
+| `collectstatic` | Exits 0, files in staticfiles/ | [ ] |
+
+## Data Migration Verification
+
+| Test | Expected | Status |
+|------|----------|--------|
+| Export runs without error | Produces export file | [ ] |
+| Import on clean DB succeeds | Exits 0 | [ ] |
+| Snippet count matches | Row count within tolerance | [ ] |
+| Language count matches | All languages present | [ ] |
+| Sample fiddle renders | Code field decompresses correctly | [ ] |
+
+## Cutover Runbook
+
+(To be written by Validation agent after all other phases complete.)
+
+1. Export data from production
+2. Deploy new codebase
+3. Import data
+4. DNS / load balancer switch
+5. Rollback plan
diff --git a/docs/modernization/old_inspectdb.txt b/docs/modernization/old_inspectdb.txt
new file mode 100644
index 0000000..c2aa298
--- /dev/null
+++ b/docs/modernization/old_inspectdb.txt
@@ -0,0 +1,23 @@
+No existing DB found.
+
+The legacy project at /Users/yuguang/Projects/pythonfiddle does not contain a
+SQLite database file. The settings.default.py references a DB named 'fiddle'
+(no path prefix, meaning it would be looked up in the current working directory),
+but no such file exists in the legacy project directory.
+
+To generate this file if a DB becomes available:
+  cd /Users/yuguang/Projects/pythonfiddle
+  python manage.py inspectdb > docs/modernization/old_inspectdb.txt
+
+The expected tables based on INSTALLED_APPS in settings.default.py:
+  - auth_user, auth_group, auth_permission (Django auth)
+  - django_content_type
+  - django_session
+  - django_site
+  - django_flatpages
+  - django_redirect
+  - social_auth_usersocialauth, social_auth_nonce, social_auth_association
+  - taggit_tag, taggit_taggeditem
+  - fiddle_language, fiddle_snippet
+  - chunks_chunk (from django-chunks)
+  - django_admin_log
diff --git a/manage.py b/manage.py
old mode 100644
new mode 100755
index 3e4eedc..15e2324
--- a/manage.py
+++ b/manage.py
@@ -1,14 +1,22 @@
 #!/usr/bin/env python
-from django.core.management import execute_manager
-import imp
-try:
-    imp.find_module('settings') # Assumed to be in the same directory.
-except ImportError:
-    import sys
-    sys.stderr.write("Error: Can't find the file 'settings.py' in the directory containing %r. It appears you've customized things.\nYou'll have to run django-admin.py, passing it your settings module.\n" % __file__)
-    sys.exit(1)
-
-import settings
-
-if __name__ == "__main__":
-    execute_manager(settings)
+"""Django's command-line utility for administrative tasks."""
+import os
+import sys
+
+
+def main():
+    """Run administrative tasks."""
+    os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'pythonfiddle_modern.settings')
+    try:
+        from django.core.management import execute_from_command_line
+    except ImportError as exc:
+        raise ImportError(
+            "Couldn't import Django. Are you sure it's installed and "
+            "available on your PYTHONPATH environment variable? Did you "
+            "forget to activate a virtual environment?"
+        ) from exc
+    execute_from_command_line(sys.argv)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/pythonfiddle_modern/__init__.py b/pythonfiddle_modern/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/pythonfiddle_modern/asgi.py b/pythonfiddle_modern/asgi.py
new file mode 100644
index 0000000..0fc361a
--- /dev/null
+++ b/pythonfiddle_modern/asgi.py
@@ -0,0 +1,16 @@
+"""
+ASGI config for pythonfiddle_modern project.
+
+It exposes the ASGI callable as a module-level variable named ``application``.
+
+For more information on this file, see
+https://docs.djangoproject.com/en/5.2/howto/deployment/asgi/
+"""
+
+import os
+
+from django.core.asgi import get_asgi_application
+
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'pythonfiddle_modern.settings')
+
+application = get_asgi_application()
diff --git a/pythonfiddle_modern/settings.py b/pythonfiddle_modern/settings.py
new file mode 100644
index 0000000..5fb33ca
--- /dev/null
+++ b/pythonfiddle_modern/settings.py
@@ -0,0 +1,215 @@
+"""
+Django settings for pythonfiddle_modern project.
+
+Generated by 'django-admin startproject' using Django 5.2.15, then
+modernized for the pythonfiddle Django 5.2 migration.
+
+See https://docs.djangoproject.com/en/5.2/topics/settings/ for details.
+"""
+
+import os
+from pathlib import Path
+
+# Build paths inside the project like this: BASE_DIR / 'subdir'.
+BASE_DIR = Path(__file__).resolve().parent.parent
+
+# Path to the shared cloud-ide-templates repository
+CLOUD_IDE_TEMPLATES_DIR = Path('/Users/yuguang/Projects/cloud-ide-templates')
+
+
+# Quick-start development settings - unsuitable for production
+# See https://docs.djangoproject.com/en/5.2/howto/deployment/checklist/
+
+# SECURITY WARNING: keep the secret key used in production secret!
+SECRET_KEY = 'django-insecure-4i1pln%%dhtff8gs0c65lb4b85_xm7u(%*i-10q9giqzv$r%1c'
+
+# SECURITY WARNING: don't run with debug turned on in production!
+DEBUG = True
+
+ALLOWED_HOSTS = ['*']
+
+
+# Application definition
+
+INSTALLED_APPS = [
+    # Whitenoise must come before staticfiles when using runserver
+    'whitenoise.runserver_nostatic',
+    # Django built-ins
+    'django.contrib.admin',
+    'django.contrib.auth',
+    'django.contrib.contenttypes',
+    'django.contrib.sessions',
+    'django.contrib.messages',
+    'django.contrib.staticfiles',
+    'django.contrib.sites',
+    'django.contrib.sitemaps',
+    # Third-party
+    'social_django',
+    'taggit',
+    # pythonfiddle / cloud_ide apps
+    'cloud_ide.fiddle',
+]
+
+MIDDLEWARE = [
+    'django.middleware.security.SecurityMiddleware',
+    # Whitenoise serves static files in production without a web server
+    'whitenoise.middleware.WhiteNoiseMiddleware',
+    'django.contrib.sessions.middleware.SessionMiddleware',
+    'django.middleware.locale.LocaleMiddleware',
+    'django.middleware.common.CommonMiddleware',
+    'django.middleware.csrf.CsrfViewMiddleware',
+    'django.contrib.auth.middleware.AuthenticationMiddleware',
+    'django.contrib.messages.middleware.MessageMiddleware',
+    'django.middleware.clickjacking.XFrameOptionsMiddleware',
+]
+
+ROOT_URLCONF = 'pythonfiddle_modern.urls'
+
+TEMPLATES = [
+    {
+        'BACKEND': 'django.template.backends.django.DjangoTemplates',
+        'DIRS': [
+            # Shared cloud-ide templates (fiddlesalad / pythonfiddle common templates)
+            CLOUD_IDE_TEMPLATES_DIR,
+            # Local project templates (overrides)
+            BASE_DIR / 'templates',
+        ],
+        'APP_DIRS': True,
+        'OPTIONS': {
+            'context_processors': [
+                'django.template.context_processors.debug',
+                'django.template.context_processors.request',
+                'django.contrib.auth.context_processors.auth',
+                'django.contrib.messages.context_processors.messages',
+                'django.template.context_processors.i18n',
+                'social_django.context_processors.backends',
+                'social_django.context_processors.login_redirect',
+            ],
+        },
+    },
+]
+
+WSGI_APPLICATION = 'pythonfiddle_modern.wsgi.application'
+
+
+# Database
+# https://docs.djangoproject.com/en/5.2/ref/settings/#databases
+
+DATABASES = {
+    'default': {
+        'ENGINE': 'django.db.backends.sqlite3',
+        'NAME': BASE_DIR / 'db.sqlite3',
+    }
+}
+
+SITE_ID = 1
+
+
+# Authentication
+# https://docs.djangoproject.com/en/5.2/topics/auth/
+
+AUTHENTICATION_BACKENDS = [
+    'social_core.backends.google.GoogleOAuth2',
+    'social_core.backends.twitter.TwitterOAuth',
+    'social_core.backends.facebook.FacebookOAuth2',
+    'django.contrib.auth.backends.ModelBackend',
+]
+
+LOGIN_URL = '/login/'
+LOGIN_REDIRECT_URL = '/'
+LOGOUT_REDIRECT_URL = '/'
+
+# Social auth namespace — must match namespace= in urls.py
+SOCIAL_AUTH_URL_NAMESPACE = 'social'
+
+# Social auth OAuth credentials (set via environment variables)
+SOCIAL_AUTH_GOOGLE_OAUTH2_KEY = os.environ.get('GOOGLE_KEY', '')
+SOCIAL_AUTH_GOOGLE_OAUTH2_SECRET = os.environ.get('GOOGLE_SECRET', '')
+SOCIAL_AUTH_TWITTER_KEY = os.environ.get('TWITTER_KEY', '')
+SOCIAL_AUTH_TWITTER_SECRET = os.environ.get('TWITTER_SECRET', '')
+SOCIAL_AUTH_FACEBOOK_KEY = os.environ.get('FACEBOOK_KEY', '')
+SOCIAL_AUTH_FACEBOOK_SECRET = os.environ.get('FACEBOOK_SECRET', '')
+
+
+# Password validation
+# https://docs.djangoproject.com/en/5.2/ref/settings/#auth-password-validators
+
+AUTH_PASSWORD_VALIDATORS = [
+    {
+        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
+    },
+    {
+        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
+    },
+    {
+        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
+    },
+    {
+        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
+    },
+]
+
+
+# Internationalization
+# https://docs.djangoproject.com/en/5.2/topics/i18n/
+
+LANGUAGE_CODE = 'en-us'
+
+LANGUAGES = [
+    ('en', 'English'),
+    ('zh', 'Chinese'),
+]
+
+LOCALE_PATHS = [
+    BASE_DIR / 'locale',
+]
+
+TIME_ZONE = 'UTC'
+
+USE_I18N = True
+
+USE_TZ = True
+
+
+# Static files (CSS, JavaScript, Images)
+# https://docs.djangoproject.com/en/5.2/howto/static-files/
+
+STATIC_URL = '/static/'
+STATIC_ROOT = BASE_DIR / 'staticfiles'
+
+# Project-level static files directory
+STATICFILES_DIRS = [
+    BASE_DIR / 'static',
+]
+
+# Whitenoise static file storage (compressed + manifest for cache-busting)
+STORAGES = {
+    'default': {
+        'BACKEND': 'django.core.files.storage.FileSystemStorage',
+    },
+    'staticfiles': {
+        'BACKEND': 'whitenoise.storage.CompressedManifestStaticFilesStorage',
+    },
+}
+
+
+# Default primary key field type
+# https://docs.djangoproject.com/en/5.2/ref/settings/#default-auto-field
+
+DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'
+
+
+# Logging
+LOGGING = {
+    'version': 1,
+    'disable_existing_loggers': False,
+    'handlers': {
+        'console': {
+            'class': 'logging.StreamHandler',
+        },
+    },
+    'root': {
+        'handlers': ['console'],
+        'level': 'WARNING',
+    },
+}
diff --git a/pythonfiddle_modern/urls.py b/pythonfiddle_modern/urls.py
new file mode 100644
index 0000000..39351b7
--- /dev/null
+++ b/pythonfiddle_modern/urls.py
@@ -0,0 +1,36 @@
+"""
+URL configuration for pythonfiddle_modern project.
+
+Ported from legacy pythonfiddle/urls.py (Django 1.4) to Django 5.2 syntax.
+See https://docs.djangoproject.com/en/5.2/topics/http/urls/ for details.
+"""
+from django.contrib import admin
+from django.contrib.auth.views import LogoutView
+from django.urls import include, path
+from django.views.generic import TemplateView
+
+urlpatterns = [
+    # Django admin
+    path('admin/', admin.site.urls),
+
+    # Internationalisation (language switch form)
+    path('i18n/', include('django.conf.urls.i18n')),
+
+    # Social auth: OAuth login/callback/disconnect endpoints (replaces django-social-auth).
+    # Provides: /social-auth/login/<backend>/, /social-auth/complete/<backend>/,
+    #           /social-auth/disconnect/<backend>/  etc.
+    # namespace='social' must match SOCIAL_AUTH_URL_NAMESPACE in settings.
+    path('social-auth/', include('social_django.urls', namespace='social')),
+
+    # Login page: renders a template with links to each social provider.
+    # Phase 5 (URLs+Templates) will supply the real login.html template;
+    # this TemplateView acts as a functional placeholder in the meantime.
+    path('login/', TemplateView.as_view(template_name='login.html'), name='login'),
+
+    # Logout: POST-only in Django 5 to prevent CSRF attacks.
+    path('logout/', LogoutView.as_view(next_page='/'), name='logout'),
+
+    # Core fiddle engine: create, save, check_title, tag_hint, open, embedded
+    # Must come last so <snippet_slug> doesn't shadow the routes above.
+    path('', include('cloud_ide.fiddle.urls')),
+]
diff --git a/pythonfiddle_modern/wsgi.py b/pythonfiddle_modern/wsgi.py
new file mode 100644
index 0000000..a2ee2bf
--- /dev/null
+++ b/pythonfiddle_modern/wsgi.py
@@ -0,0 +1,16 @@
+"""
+WSGI config for pythonfiddle_modern project.
+
+It exposes the WSGI callable as a module-level variable named ``application``.
+
+For more information on this file, see
+https://docs.djangoproject.com/en/5.2/howto/deployment/wsgi/
+"""
+
+import os
+
+from django.core.wsgi import get_wsgi_application
+
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'pythonfiddle_modern.settings')
+
+application = get_wsgi_application()
diff --git a/requirements.txt b/requirements.txt
index 9ae6ebf..a3a21ef 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,16 @@
-django == 1.4.16
-django-mediasync >= 2.2.0
-django-social-auth >= 0.6.4
-django-taggit >= 0.9.3
-django-chunks >= 0.1
+# Django 5.2 LTS + modern replacements for legacy Django 1.4 packages
+# Legacy package -> replacement:
+#   django==1.4.16         -> Django>=5.2,<5.3
+#   django-mediasync       -> whitenoise (static files)
+#   django-social-auth     -> social-auth-core + social-auth-app-django
+#   django-taggit          -> django-taggit (still maintained)
+#   django-chunks          -> removed (use Django flatpages or custom snippets)
+
+Django>=5.2,<5.3
+social-auth-core
+social-auth-app-django
+django-taggit
+whitenoise
+
+# cloud_ide (local editable install -- see COMPLETION.md for setup)
+# pip install -e /Users/yuguang/Projects/django-cloud-ide
diff --git a/scripts/README.md b/scripts/README.md
new file mode 100644
index 0000000..32fe83f
--- /dev/null
+++ b/scripts/README.md
@@ -0,0 +1,165 @@
+# Migration Scripts
+
+These scripts migrate data from the legacy Django 1.4 pythonfiddle SQLite database
+into the modern Django 5.2 schema.
+
+---
+
+## export_legacy_data.py
+
+Reads the legacy SQLite DB and writes a portable JSON file.  
+**Does not require Django** — uses `sqlite3` from the standard library.
+
+### Usage
+
+```bash
+# From the project root (venv active)
+python scripts/export_legacy_data.py [DB_PATH [OUTPUT_PATH]]
+```
+
+| Argument | Default | Description |
+|---|---|---|
+| `DB_PATH` | `../pythonfiddle/fiddle` | Path to the legacy SQLite file (no `.sqlite` extension in legacy repo) |
+| `OUTPUT_PATH` | `legacy_export.json` | Output JSON file |
+
+### Example
+
+```bash
+# Export from the legacy repo sibling directory
+python scripts/export_legacy_data.py ../pythonfiddle/fiddle legacy_export.json
+
+# Export from an explicit dump
+python scripts/export_legacy_data.py /tmp/prod_backup.sqlite legacy_export.json
+```
+
+### Output format
+
+```json
+{
+  "exported_at": "2026-06-13T23:00:00+00:00",
+  "source_db": "/path/to/fiddle",
+  "row_counts": { "languages": 5, "snippets": 1234 },
+  "languages": [
+    { "id": 1, "name": "python" }
+  ],
+  "snippets": [
+    {
+      "id": 1,
+      "title": "Hello World",
+      "slug": "hello-world",
+      "author_id": 3,
+      "author_username": "alice",
+      "description": "",
+      "tags": ["demo", "python"],
+      "last_modified": "2014-03-01 10:00:00",
+      "code": "print('hello')",
+      "language_id": 1
+    }
+  ]
+}
+```
+
+### CompressedTextField handling
+
+The `code` column is stored as a **gzip-compressed blob** by `CompressedTextField`.
+The export script tries decompression in this order:
+
+1. **gzip** (standard, used by `compress_string` in `compression.py`)
+2. **zlib** (fallback for alternate legacy encoding)
+3. **UTF-8 bytes** (uncompressed rows)
+4. **Latin-1** (byte-safe fallback)
+
+---
+
+## import_legacy_data.py
+
+Reads `legacy_export.json` and populates the Django DB via the ORM.  
+**Requires Django** — run from the project root with the virtualenv active.
+
+### Usage
+
+```bash
+# From the project root (venv active)
+python scripts/import_legacy_data.py [INPUT_PATH]
+```
+
+| Argument | Default | Description |
+|---|---|---|
+| `INPUT_PATH` | `legacy_export.json` | JSON file produced by the export script |
+
+### Example
+
+```bash
+python scripts/import_legacy_data.py legacy_export.json
+```
+
+### Behaviour
+
+| Object | Strategy |
+|---|---|
+| `Language` | `get_or_create` by `name` |
+| `Snippet` | `create` (see warning below) |
+| Author lookup | Username first, then numeric id; falls back to `legacy_import_user` |
+| Tags | `snippet.tags.set(*tags)` after creation |
+
+> **Warning:** Running this script twice will create duplicate snippets.
+> Clear the snippet and language tables before re-running:
+> ```bash
+> python manage.py shell -c "
+> from cloud_ide.fiddle.models import Snippet, Language
+> Snippet.objects.all().delete()
+> Language.objects.all().delete()
+> "
+> ```
+
+### Skipped rows
+
+Any row that cannot be imported (missing language reference, unexpected exception)
+is logged as a warning and listed in the summary at the end.
+
+---
+
+## Full roundtrip example
+
+```bash
+# 1. Activate virtualenv
+source .venv/bin/activate
+
+# 2. Ensure migrations are applied
+python manage.py migrate
+
+# 3. Seed test data
+python manage.py shell -c "
+from cloud_ide.fiddle.models import Language, Snippet
+from django.contrib.auth.models import User
+u, _ = User.objects.get_or_create(username='testuser')
+lang, _ = Language.objects.get_or_create(name='Python')
+s = Snippet.objects.create(title='Hello', author=u, language=lang, code='print(\"hello\")')
+s.tags.add('demo', 'python')
+print('Created snippet id:', s.id)
+"
+
+# 4. Export
+python scripts/export_legacy_data.py db.sqlite3 legacy_export.json
+
+# 5. Verify export
+python -c "
+import json
+d = json.load(open('legacy_export.json'))
+print('Languages:', len(d['languages']), 'Snippets:', len(d['snippets']))
+"
+
+# 6. (Optional) wipe and re-import into a fresh DB
+python manage.py shell -c "
+from cloud_ide.fiddle.models import Snippet, Language
+Snippet.objects.all().delete(); Language.objects.all().delete()
+"
+python scripts/import_legacy_data.py legacy_export.json
+
+# 7. Verify import
+python manage.py shell -c "
+from cloud_ide.fiddle.models import Snippet, Language
+print('Languages:', Language.objects.count())
+print('Snippets:', Snippet.objects.count())
+"
+```
diff --git a/scripts/__init__.py b/scripts/__init__.py
new file mode 100644
index 0000000..246db6f
--- /dev/null
+++ b/scripts/__init__.py
@@ -0,0 +1 @@
+# scripts package
diff --git a/scripts/export_legacy_data.py b/scripts/export_legacy_data.py
new file mode 100644
index 0000000..29aad56
--- /dev/null
+++ b/scripts/export_legacy_data.py
@@ -0,0 +1,241 @@
+#!/usr/bin/env python3
+"""
+Export legacy pythonfiddle SQLite database to a JSON file.
+
+Does NOT require Django to be installed or configured.
+Uses the stdlib sqlite3 module directly.
+
+Usage:
+    python scripts/export_legacy_data.py [DB_PATH [OUTPUT_PATH]]
+
+    DB_PATH:     Path to the legacy SQLite DB file.
+                 Default: ../pythonfiddle/fiddle  (sibling repo, no extension)
+    OUTPUT_PATH: Path for the output JSON file.
+                 Default: legacy_export.json  (project root)
+
+The code field (CompressedTextField) is stored as a gzip-compressed blob.
+This script decompresses it transparently, falling back to zlib and then
+raw UTF-8 decode for rows that were stored uncompressed.
+"""
+
+import gzip
+import io
+import json
+import os
+import sqlite3
+import sys
+import zlib
+from datetime import datetime, timezone
+
+# ---------------------------------------------------------------------------
+# Defaults
+# ---------------------------------------------------------------------------
+_SCRIPTS_DIR = os.path.dirname(os.path.abspath(__file__))
+_PROJECT_ROOT = os.path.dirname(_SCRIPTS_DIR)
+
+DEFAULT_DB_PATH = os.path.join(_PROJECT_ROOT, '..', 'pythonfiddle', 'fiddle')
+DEFAULT_OUTPUT_PATH = os.path.join(_PROJECT_ROOT, 'legacy_export.json')
+
+
+# ---------------------------------------------------------------------------
+# Decompression helpers
+# ---------------------------------------------------------------------------
+
+def decompress_code(raw):
+    """Decompress a code blob from the legacy DB.
+
+    CompressedTextField stores text as gzip-compressed bytes.
+    Legacy rows may have been inserted without compression (plain text bytes
+    or actual str if the SQLite driver decoded them).
+
+    Returns a UTF-8 string, or None if *raw* is None.
+    """
+    if raw is None:
+        return None
+    if isinstance(raw, str):
+        # Already plain text (uncompressed legacy row or already decoded)
+        return raw
+    if not isinstance(raw, (bytes, bytearray)):
+        return str(raw)
+
+    # 1) Try gzip (standard CompressedTextField format)
+    try:
+        with gzip.GzipFile(fileobj=io.BytesIO(raw)) as gz:
+            return gz.read().decode('utf-8')
+    except Exception:
+        pass
+
+    # 2) Try zlib (alternative compression sometimes used in older versions)
+    try:
+        return zlib.decompress(raw).decode('utf-8')
+    except Exception:
+        pass
+
+    # 3) Plain UTF-8 bytes (uncompressed)
+    try:
+        return raw.decode('utf-8')
+    except Exception:
+        pass
+
+    # 4) Latin-1 fallback — lossless decode of arbitrary bytes
+    try:
+        return raw.decode('latin-1')
+    except Exception:
+        return repr(raw)
+
+
+# ---------------------------------------------------------------------------
+# Main export
+# ---------------------------------------------------------------------------
+
+def export_db(db_path: str, output_path: str) -> None:
+    db_path = os.path.abspath(db_path)
+    output_path = os.path.abspath(output_path)
+
+    print(f"Source DB:  {db_path}")
+    print(f"Output:     {output_path}")
+
+    if not os.path.exists(db_path):
+        print(f"ERROR: DB file not found: {db_path}", file=sys.stderr)
+        sys.exit(1)
+
+    conn = sqlite3.connect(db_path)
+    conn.row_factory = sqlite3.Row
+    cur = conn.cursor()
+
+    # Discover which tables exist
+    cur.execute("SELECT name FROM sqlite_master WHERE type='table' ORDER BY name")
+    tables = {row[0] for row in cur.fetchall()}
+    print(f"Tables:     {', '.join(sorted(tables))}")
+
+    # ------------------------------------------------------------------
+    # Languages
+    # ------------------------------------------------------------------
+    languages = []
+    if 'fiddle_language' in tables:
+        cur.execute("SELECT id, name FROM fiddle_language ORDER BY id")
+        for row in cur.fetchall():
+            languages.append({'id': row['id'], 'name': row['name']})
+
+    # ------------------------------------------------------------------
+    # Snippets (with author username + tags)
+    # ------------------------------------------------------------------
+    snippets = []
+    if 'fiddle_snippet' in tables:
+        # Join auth_user to capture author_username for the import script
+        if 'auth_user' in tables:
+            cur.execute("""
+                SELECT s.id,
+                       s.title,
+                       s.slug,
+                       s.author_id,
+                       u.username  AS author_username,
+                       s.description,
+                       s.last_modified,
+                       s.code,
+                       s.language_id
+                FROM fiddle_snippet s
+                LEFT JOIN auth_user u ON u.id = s.author_id
+                ORDER BY s.id
+            """)
+        else:
+            cur.execute("""
+                SELECT id, title, slug, author_id,
+                       NULL AS author_username,
+                       description, last_modified, code, language_id
+                FROM fiddle_snippet
+                ORDER BY id
+            """)
+
+        for row in cur.fetchall():
+            snippet_id = row['id']
+
+            # Resolve tags via taggit tables
+            tags = _get_tags_for_snippet(cur, tables, snippet_id)
+
+            # Decompress code blob
+            code_text = decompress_code(row['code'])
+
+            snippets.append({
+                'id': snippet_id,
+                'title': row['title'],
+                'slug': row['slug'],
+                'author_id': row['author_id'],
+                'author_username': row['author_username'],
+                'description': row['description'] or '',
+                'tags': tags,
+                'last_modified': row['last_modified'],
+                'code': code_text,
+                'language_id': row['language_id'],
+            })
+
+    conn.close()
+
+    # ------------------------------------------------------------------
+    # Assemble and write JSON
+    # ------------------------------------------------------------------
+    export_data = {
+        'exported_at': datetime.now(timezone.utc).isoformat(),
+        'source_db': db_path,
+        'row_counts': {
+            'languages': len(languages),
+            'snippets': len(snippets),
+        },
+        'languages': languages,
+        'snippets': snippets,
+    }
+
+    with open(output_path, 'w', encoding='utf-8') as f:
+        json.dump(export_data, f, indent=2, ensure_ascii=False, default=str)
+
+    print()
+    print("Export complete:")
+    print(f"  Languages: {len(languages)}")
+    print(f"  Snippets:  {len(snippets)}")
+    print(f"  Written:   {output_path}")
+
+
+def _get_tags_for_snippet(cur, tables, snippet_id):
+    """Return a list of tag name strings for the given snippet ID."""
+    if 'taggit_tag' not in tables or 'taggit_taggeditem' not in tables:
+        return []
+
+    # Prefer to filter by content type so we don't cross-contaminate if other
+    # taggable models exist.
+    if 'django_content_type' in tables:
+        try:
+            cur.execute("""
+                SELECT t.name
+                FROM taggit_tag t
+                JOIN taggit_taggeditem ti ON ti.tag_id = t.id
+                JOIN django_content_type ct ON ct.id = ti.content_type_id
+                WHERE ct.model = 'snippet'
+                  AND CAST(ti.object_id AS INTEGER) = ?
+                ORDER BY t.name
+            """, (snippet_id,))
+            return [r[0] for r in cur.fetchall()]
+        except sqlite3.OperationalError:
+            pass  # fall through
+
+    # Fallback: join without content-type filter
+    try:
+        cur.execute("""
+            SELECT t.name
+            FROM taggit_tag t
+            JOIN taggit_taggeditem ti ON ti.tag_id = t.id
+            WHERE CAST(ti.object_id AS INTEGER) = ?
+            ORDER BY t.name
+        """, (snippet_id,))
+        return [r[0] for r in cur.fetchall()]
+    except sqlite3.OperationalError:
+        return []
+
+
+# ---------------------------------------------------------------------------
+# Entry point
+# ---------------------------------------------------------------------------
+
+if __name__ == '__main__':
+    _db = sys.argv[1] if len(sys.argv) > 1 else DEFAULT_DB_PATH
+    _out = sys.argv[2] if len(sys.argv) > 2 else DEFAULT_OUTPUT_PATH
+    export_db(_db, _out)
diff --git a/scripts/import_legacy_data.py b/scripts/import_legacy_data.py
new file mode 100644
index 0000000..0ab1af0
--- /dev/null
+++ b/scripts/import_legacy_data.py
@@ -0,0 +1,213 @@
+#!/usr/bin/env python3
+"""
+Import legacy pythonfiddle data from a JSON export file into the modern Django DB.
+
+Requires the Django project to be on PYTHONPATH (run from project root).
+
+Usage:
+    python scripts/import_legacy_data.py [INPUT_PATH]
+
+    INPUT_PATH: Path to the JSON export file produced by export_legacy_data.py
+                Default: legacy_export.json  (project root)
+
+Behaviour:
+  - Language  → get_or_create by name
+  - Snippet   → created fresh; if the author_id/username does not exist in the
+                new DB a placeholder user ("legacy_import_user") is used instead
+  - Tags      → re-applied via snippet.tags.set()
+  - Skipped rows are logged with a reason; a summary is printed at the end
+
+WARNING: Running this script against a DB that already contains snippet data
+will create duplicate snippets.  Clear the snippet / language tables before
+re-running if you need a clean import.
+"""
+
+import json
+import logging
+import os
+import sys
+
+# ---------------------------------------------------------------------------
+# Bootstrap Django
+# ---------------------------------------------------------------------------
+_SCRIPTS_DIR = os.path.dirname(os.path.abspath(__file__))
+_PROJECT_ROOT = os.path.dirname(_SCRIPTS_DIR)
+sys.path.insert(0, _PROJECT_ROOT)
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'pythonfiddle_modern.settings')
+
+import django  # noqa: E402
+django.setup()
+
+from django.contrib.auth.models import User          # noqa: E402
+from cloud_ide.fiddle.models import Language, Snippet  # noqa: E402
+
+# ---------------------------------------------------------------------------
+# Logging
+# ---------------------------------------------------------------------------
+logging.basicConfig(level=logging.INFO, format='%(levelname)s: %(message)s')
+log = logging.getLogger(__name__)
+
+# ---------------------------------------------------------------------------
+# Constants
+# ---------------------------------------------------------------------------
+DEFAULT_INPUT_PATH = os.path.join(_PROJECT_ROOT, 'legacy_export.json')
+PLACEHOLDER_USERNAME = 'legacy_import_user'
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+def _get_placeholder_user():
+    """Return (and lazily create) the fallback author for orphaned snippets."""
+    user, created = User.objects.get_or_create(
+        username=PLACEHOLDER_USERNAME,
+        defaults={'email': 'legacy@pythonfiddle.example', 'is_active': True},
+    )
+    if created:
+        log.info("Created placeholder user: %s", PLACEHOLDER_USERNAME)
+    return user
+
+
+# ---------------------------------------------------------------------------
+# Main import
+# ---------------------------------------------------------------------------
+
+def import_data(input_path: str) -> None:
+    input_path = os.path.abspath(input_path)
+    log.info("Reading: %s", input_path)
+
+    if not os.path.exists(input_path):
+        log.error("Input file not found: %s", input_path)
+        sys.exit(1)
+
+    with open(input_path, encoding='utf-8') as f:
+        data = json.load(f)
+
+    log.info("Source DB:   %s", data.get('source_db', 'unknown'))
+    log.info("Exported at: %s", data.get('exported_at', 'unknown'))
+    log.info("Expected:    %s languages, %s snippets",
+             data['row_counts']['languages'], data['row_counts']['snippets'])
+
+    # ------------------------------------------------------------------
+    # 1. Languages — get_or_create by name
+    # ------------------------------------------------------------------
+    lang_map: dict[int, Language] = {}  # legacy id → new Language object
+    lang_created = lang_existing = 0
+
+    for rec in data.get('languages', []):
+        lang, created = Language.objects.get_or_create(name=rec['name'])
+        lang_map[rec['id']] = lang
+        if created:
+            lang_created += 1
+            log.info("  [lang] Created: %s", lang.name)
+        else:
+            lang_existing += 1
+
+    log.info("Languages: %d created, %d already existed", lang_created, lang_existing)
+
+    # ------------------------------------------------------------------
+    # 2. Snippets
+    # ------------------------------------------------------------------
+    snippet_created = 0
+    snippet_skipped = 0
+    skipped: list[str] = []
+    placeholder: User | None = None
+
+    for rec in data.get('snippets', []):
+        legacy_id = rec.get('id', '?')
+        title = rec.get('title', '')
+
+        # Resolve language
+        language = lang_map.get(rec.get('language_id'))
+        if language is None:
+            reason = (
+                f"id={legacy_id} title='{title}': "
+                f"language_id={rec.get('language_id')} not found in export"
+            )
+            log.warning("SKIP: %s", reason)
+            skipped.append(reason)
+            snippet_skipped += 1
+            continue
+
+        # Resolve author — try by id then by username, fall back to placeholder
+        author = _resolve_author(rec)
+        if author is None:
+            if placeholder is None:
+                placeholder = _get_placeholder_user()
+            author = placeholder
+            log.warning(
+                "  [snippet] id=%s '%s': author not found (id=%s, username=%s) "
+                "→ placeholder",
+                legacy_id, title, rec.get('author_id'), rec.get('author_username'),
+            )
+
+        # Create the snippet
+        code = rec.get('code') or ''
+        try:
+            snippet = Snippet.objects.create(
+                title=title,
+                author=author,
+                description=rec.get('description') or '',
+                code=code,
+                language=language,
+            )
+            # Re-apply tags
+            tags = rec.get('tags') or []
+            if tags:
+                snippet.tags.set(tags)
+            snippet_created += 1
+            log.info("  [snippet] Created: '%s' [%s] tags=%s", title, language.name, tags)
+
+        except Exception as exc:
+            reason = f"id={legacy_id} title='{title}': {exc}"
+            log.error("SKIP (error): %s", reason)
+            skipped.append(reason)
+            snippet_skipped += 1
+
+    # ------------------------------------------------------------------
+    # Summary
+    # ------------------------------------------------------------------
+    print()
+    print("=" * 40)
+    print("Import summary")
+    print("=" * 40)
+    print(f"  Languages total:   {Language.objects.count()}")
+    print(f"  Snippets total:    {Snippet.objects.count()}")
+    print(f"  Snippets created:  {snippet_created}")
+    print(f"  Snippets skipped:  {snippet_skipped}")
+    if skipped:
+        print()
+        print("Skipped rows:")
+        for reason in skipped:
+            print(f"  • {reason}")
+
+
+def _resolve_author(rec: dict):
+    """Try to find an existing User; return None if not found."""
+    # 1) Look up by username (most reliable cross-DB)
+    username = rec.get('author_username')
+    if username:
+        try:
+            return User.objects.get(username=username)
+        except User.DoesNotExist:
+            pass
+
+    # 2) Fall back to numeric id (only useful if user table was also migrated)
+    author_id = rec.get('author_id')
+    if author_id is not None:
+        try:
+            return User.objects.get(id=author_id)
+        except User.DoesNotExist:
+            pass
+
+    return None
+
+
+# ---------------------------------------------------------------------------
+# Entry point
+# ---------------------------------------------------------------------------
+
+if __name__ == '__main__':
+    _inp = sys.argv[1] if len(sys.argv) > 1 else DEFAULT_INPUT_PATH
+    import_data(_inp)
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