diff --git a/backend/backend/__init__.py b/backend/backend/__init__.py
index e69de29bb..9e0d95fd7 100644
--- a/backend/backend/__init__.py
+++ b/backend/backend/__init__.py
@@ -0,0 +1,3 @@
+from .celery import app as celery_app
+
+__all__ = ('celery_app',)
\ No newline at end of file
diff --git a/backend/backend/celery.py b/backend/backend/celery.py
new file mode 100644
index 000000000..70bdb1623
--- /dev/null
+++ b/backend/backend/celery.py
@@ -0,0 +1,27 @@
+import os
+from celery import Celery
+from celery.schedules import crontab
+
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'backend.settings')
+
+
+app = Celery('backend')
+app.config_from_object('django.conf:settings', namespace='CELERY')
+app.autodiscover_tasks()
+
+# Celery Beat Schedule
+app.conf.beat_schedule = {
+    'cleanup-old-conversations': {
+        'task': 'chat.tasks.cleanup_old_conversations',
+        'schedule': crontab(hour=2, minute=0),  # Daily at 2 AM
+        'args': (30,)  # Delete conversations older than 30 days
+    },
+    'generate-missing-summaries': {
+        'task': 'chat.tasks.generate_missing_summaries',
+        'schedule': crontab(hour=3, minute=0),  # Daily at 3 AM
+    },
+}
+
+@app.task(bind=True)
+def debug_task(self):
+    print(f'Request: {self.request!r}')
\ No newline at end of file
diff --git a/backend/backend/settings.py b/backend/backend/settings.py
index 9de4f024a..50b0b30e7 100644
--- a/backend/backend/settings.py
+++ b/backend/backend/settings.py
@@ -15,17 +15,19 @@
 
 from dotenv import load_dotenv
 
-load_dotenv()
+
 
 # Build paths inside the project like this: BASE_DIR / 'subdir'.
 BASE_DIR = Path(__file__).resolve().parent.parent
+load_dotenv(os.path.join(BASE_DIR, ".env"))
 
 # Quick-start development settings - unsuitable for production
 # See https://docs.djangoproject.com/en/4.2/howto/deployment/checklist/
 
 # SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = os.environ["DJANGO_SECRET_KEY"]
-FRONTEND_URL = os.environ["FRONTEND_URL"]
+SECRET_KEY = os.environ.get("DJANGO_SECRET_KEY", "fallback-secret-key") 
+print("SECRET:", os.environ.get("DJANGO_SECRET_KEY"))   
+FRONTEND_URL = os.environ.get("FRONTEND_URL", "http://localhost:3000")
 
 # SECURITY WARNING: don't run with debug turned on in production!
 DEBUG = True
@@ -85,9 +87,13 @@
 # https://docs.djangoproject.com/en/4.2/ref/settings/#databases
 
 DATABASES = {
-    "default": {
-        "ENGINE": "django.db.backends.sqlite3",
-        "NAME": BASE_DIR / "db.sqlite3",
+    'default': {
+        'ENGINE': 'django.db.backends.postgresql',
+        'NAME': 'chatgpt_db',
+        'USER': 'chatgpt_user',
+        'PASSWORD': 'chatgpt_password',
+        'HOST': 'localhost',
+        'PORT': '5432',
     }
 }
 
@@ -149,3 +155,13 @@
 SESSION_COOKIE_SECURE = True
 CSRF_COOKIE_SECURE = True
 CSRF_COOKIE_SAMESITE = "None"
+
+# Celery Configuration
+CELERY_BROKER_URL = os.getenv('CELERY_BROKER_URL', 'redis://localhost:6379/0')
+CELERY_RESULT_BACKEND = os.getenv('CELERY_RESULT_BACKEND', 'redis://localhost:6379/0')
+CELERY_ACCEPT_CONTENT = ['json']
+CELERY_TASK_SERIALIZER = 'json'
+CELERY_RESULT_SERIALIZER = 'json'
+CELERY_TIMEZONE = 'UTC'
+CELERY_TASK_TRACK_STARTED = True
+CELERY_TASK_TIME_LIMIT = 30 * 60  # 30 minutes
\ No newline at end of file
diff --git a/backend/chat/admin.py b/backend/chat/admin.py
index a4e7d15fc..2917f9875 100644
--- a/backend/chat/admin.py
+++ b/backend/chat/admin.py
@@ -1,7 +1,7 @@
 from django.contrib import admin
 from django.utils import timezone
 from nested_admin.nested import NestedModelAdmin, NestedStackedInline, NestedTabularInline
-
+from django.utils.html import format_html
 from chat.models import Conversation, Message, Role, Version
 
 
@@ -51,8 +51,8 @@ def queryset(self, request, queryset):
 class ConversationAdmin(NestedModelAdmin):
     actions = ["undelete_selected", "soft_delete_selected"]
     inlines = [VersionInline]
-    list_display = ("title", "id", "created_at", "modified_at", "deleted_at", "version_count", "is_deleted", "user")
-    list_filter = (DeletedListFilter,)
+    list_display = ("title", "id", "created_at", "modified_at", "deleted_at", "version_count", "is_deleted",  "has_summary", "summary_status", "user")
+    list_filter = (DeletedListFilter,"is_summary_stale",)
     ordering = ("-modified_at",)
 
     def undelete_selected(self, request, queryset):
@@ -79,7 +79,27 @@ def is_deleted(self, obj):
 
     is_deleted.boolean = True
     is_deleted.short_description = "Deleted?"
-
+    def has_summary(self, obj):
+        """Display if conversation has summary"""
+        if obj.summary:
+            return format_html(
+                '<span style="color: green;">✓ Has Summary</span>'
+            )
+        return format_html(
+            '<span style="color: red;">✗ No Summary</span>'
+        )
+    has_summary.short_description = "Summary Status"
+
+    def summary_status(self, obj):
+        """Show if summary is stale"""
+        if obj.is_summary_stale:
+            return format_html(
+                '<span style="color: orange;">Stale</span>'
+            )
+        return format_html(
+            '<span style="color: green;">Current</span>'
+        )
+    summary_status.short_description = "Summary Freshness"
 
 class VersionAdmin(NestedModelAdmin):
     inlines = [MessageInline]
diff --git a/backend/chat/apps.py b/backend/chat/apps.py
index 5f75238d2..77de7129e 100644
--- a/backend/chat/apps.py
+++ b/backend/chat/apps.py
@@ -4,3 +4,6 @@
 class ChatConfig(AppConfig):
     default_auto_field = "django.db.models.BigAutoField"
     name = "chat"
+
+    def ready(self):
+        import chat.signals
\ No newline at end of file
diff --git a/backend/chat/management/commands/cleanup_conversations.py b/backend/chat/management/commands/cleanup_conversations.py
new file mode 100644
index 000000000..2000cf848
--- /dev/null
+++ b/backend/chat/management/commands/cleanup_conversations.py
@@ -0,0 +1,68 @@
+from django.core.management.base import BaseCommand
+from django.utils.timezone import now
+from django.db.models import Count
+from datetime import timedelta
+from chat.models import Conversation
+import logging
+
+logger = logging.getLogger(__name__)
+
+class Command(BaseCommand):
+    help = 'Clean up old conversations based on age'
+    
+    def add_arguments(self, parser):
+        parser.add_argument(
+            '--days',
+            type=int,
+            default=30,
+            help='Delete conversations older than specified days (default: 30)'
+        )
+        parser.add_argument(
+            '--dry-run',
+            action='store_true',
+            help='Show what would be deleted without actually deleting'
+        )
+        parser.add_argument(
+            '--user',
+            type=str,
+            help='Only delete conversations for specific user'
+        )
+    
+    def handle(self, *args, **options):
+        days = options['days']
+        dry_run = options['dry_run']
+        user_filter = options.get('user')
+        
+        cutoff_date = now() - timedelta(days=days)
+        queryset = Conversation.objects.filter(created_at__lt=cutoff_date)
+        
+        if user_filter:
+            queryset = queryset.filter(user__username=user_filter)
+        
+        count = queryset.count()
+        
+        if count == 0:
+            self.stdout.write(
+                self.style.WARNING('No conversations found matching criteria')
+            )
+            return
+        
+        self.stdout.write(f"Conversations to delete: {count}\n")
+        
+        if dry_run:
+            self.stdout.write(self.style.WARNING('DRY RUN - No deletions made\n'))
+            for conv in queryset[:5]:
+                self.stdout.write(
+                    f"  - {conv.title} ({conv.messages.count()} messages)"
+                )
+            return
+        
+        confirm = input(f"Delete {count} conversations? (yes/no): ")
+        
+        if confirm.lower() == 'yes':
+            deleted_count = queryset.delete()[0]
+            self.stdout.write(
+                self.style.SUCCESS(f'✓ Deleted {deleted_count} conversations')
+            )
+        else:
+            self.stdout.write(self.style.WARNING('Deletion cancelled'))
\ No newline at end of file
diff --git a/backend/chat/migrations/0002_activitylog_filepermission_uploadedfile_userrole_and_more.py b/backend/chat/migrations/0002_activitylog_filepermission_uploadedfile_userrole_and_more.py
new file mode 100644
index 000000000..99c92bf53
--- /dev/null
+++ b/backend/chat/migrations/0002_activitylog_filepermission_uploadedfile_userrole_and_more.py
@@ -0,0 +1,162 @@
+# Generated by Django 5.2.11 on 2026-02-28 06:51
+
+import django.db.models.deletion
+import uuid
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('chat', '0001_initial'),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='ActivityLog',
+            fields=[
+                ('id', models.UUIDField(default=uuid.uuid4, editable=False, primary_key=True, serialize=False)),
+                ('action', models.CharField(choices=[('file_upload', 'File Upload'), ('file_delete', 'File Delete'), ('file_access', 'File Access'), ('conversation_create', 'Conversation Create'), ('conversation_delete', 'Conversation Delete'), ('conversation_edit', 'Conversation Edit'), ('message_send', 'Message Send'), ('summary_generate', 'Summary Generate'), ('summary_regenerate', 'Summary Regenerate')], max_length=50)),
+                ('resource_type', models.CharField(max_length=50)),
+                ('resource_id', models.CharField(blank=True, max_length=100, null=True)),
+                ('details', models.JSONField(blank=True, default=dict)),
+                ('ip_address', models.GenericIPAddressField(blank=True, null=True)),
+                ('user_agent', models.TextField(blank=True)),
+                ('status', models.CharField(choices=[('success', 'Success'), ('failed', 'Failed')], default='success', max_length=20)),
+                ('timestamp', models.DateTimeField(auto_now_add=True, db_index=True)),
+            ],
+            options={
+                'ordering': ['-timestamp'],
+            },
+        ),
+        migrations.CreateModel(
+            name='FilePermission',
+            fields=[
+                ('id', models.UUIDField(default=uuid.uuid4, editable=False, primary_key=True, serialize=False)),
+                ('permission', models.CharField(choices=[('view', 'View'), ('upload', 'Upload'), ('delete', 'Delete'), ('share', 'Share')], max_length=20)),
+                ('created_at', models.DateTimeField(auto_now_add=True)),
+            ],
+        ),
+        migrations.CreateModel(
+            name='UploadedFile',
+            fields=[
+                ('id', models.UUIDField(default=uuid.uuid4, editable=False, primary_key=True, serialize=False)),
+                ('file', models.FileField(upload_to='uploads/%Y/%m/%d/')),
+                ('filename', models.CharField(max_length=255)),
+                ('file_size', models.BigIntegerField()),
+                ('file_type', models.CharField(max_length=50)),
+                ('file_hash', models.CharField(max_length=64, unique=True)),
+                ('status', models.CharField(choices=[('pending', 'Pending'), ('processing', 'Processing'), ('completed', 'Completed'), ('failed', 'Failed')], default='pending', max_length=20)),
+                ('uploaded_at', models.DateTimeField(auto_now_add=True)),
+                ('processed_at', models.DateTimeField(blank=True, null=True)),
+                ('error_message', models.TextField(blank=True, null=True)),
+                ('mime_type', models.CharField(blank=True, max_length=100, null=True)),
+                ('page_count', models.IntegerField(blank=True, null=True)),
+                ('is_indexed', models.BooleanField(default=False)),
+            ],
+            options={
+                'ordering': ['-uploaded_at'],
+            },
+        ),
+        migrations.CreateModel(
+            name='UserRole',
+            fields=[
+                ('id', models.UUIDField(default=uuid.uuid4, editable=False, primary_key=True, serialize=False)),
+                ('role', models.CharField(choices=[('user', 'Regular User'), ('moderator', 'Moderator'), ('admin', 'Administrator')], default='user', max_length=20)),
+                ('created_at', models.DateTimeField(auto_now_add=True)),
+                ('updated_at', models.DateTimeField(auto_now=True)),
+            ],
+        ),
+        migrations.AlterModelOptions(
+            name='conversation',
+            options={'ordering': ['-created_at']},
+        ),
+        migrations.AddField(
+            model_name='conversation',
+            name='is_summary_stale',
+            field=models.BooleanField(default=False, help_text='Indicates if summary needs to be regenerated'),
+        ),
+        migrations.AddField(
+            model_name='conversation',
+            name='summary',
+            field=models.TextField(blank=True, help_text='Auto-generated summary of the conversation', null=True),
+        ),
+        migrations.AddField(
+            model_name='conversation',
+            name='summary_generated_at',
+            field=models.DateTimeField(blank=True, help_text='Timestamp when summary was generated', null=True),
+        ),
+        migrations.AddIndex(
+            model_name='conversation',
+            index=models.Index(fields=['user', '-created_at'], name='chat_conver_user_id_49b34c_idx'),
+        ),
+        migrations.AddIndex(
+            model_name='conversation',
+            index=models.Index(fields=['is_summary_stale'], name='chat_conver_is_summ_c1de9d_idx'),
+        ),
+        migrations.AddField(
+            model_name='activitylog',
+            name='user',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='activity_logs', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AddField(
+            model_name='filepermission',
+            name='granted_by',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='granted_permissions', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AddField(
+            model_name='filepermission',
+            name='user',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='file_permissions', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AddField(
+            model_name='uploadedfile',
+            name='conversation',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='files', to='chat.conversation'),
+        ),
+        migrations.AddField(
+            model_name='uploadedfile',
+            name='user',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='uploaded_files', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AddField(
+            model_name='filepermission',
+            name='file',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='permissions', to='chat.uploadedfile'),
+        ),
+        migrations.AddField(
+            model_name='userrole',
+            name='user',
+            field=models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, related_name='role_profile', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AddIndex(
+            model_name='activitylog',
+            index=models.Index(fields=['user', '-timestamp'], name='chat_activi_user_id_a7ffef_idx'),
+        ),
+        migrations.AddIndex(
+            model_name='activitylog',
+            index=models.Index(fields=['action', '-timestamp'], name='chat_activi_action_c91d2c_idx'),
+        ),
+        migrations.AddIndex(
+            model_name='activitylog',
+            index=models.Index(fields=['resource_type', 'resource_id'], name='chat_activi_resourc_9d4685_idx'),
+        ),
+        migrations.AddIndex(
+            model_name='uploadedfile',
+            index=models.Index(fields=['user', '-uploaded_at'], name='chat_upload_user_id_618957_idx'),
+        ),
+        migrations.AddIndex(
+            model_name='uploadedfile',
+            index=models.Index(fields=['file_hash'], name='chat_upload_file_ha_43c6d5_idx'),
+        ),
+        migrations.AddIndex(
+            model_name='uploadedfile',
+            index=models.Index(fields=['status'], name='chat_upload_status_97172d_idx'),
+        ),
+        migrations.AlterUniqueTogether(
+            name='filepermission',
+            unique_together={('user', 'file', 'permission')},
+        ),
+    ]
diff --git a/backend/chat/models.py b/backend/chat/models.py
index 242788f14..be41820a8 100644
--- a/backend/chat/models.py
+++ b/backend/chat/models.py
@@ -1,5 +1,5 @@
 import uuid
-
+import hashlib
 from django.db import models
 
 from authentication.models import CustomUser
@@ -22,7 +22,28 @@ class Conversation(models.Model):
     )
     deleted_at = models.DateTimeField(null=True, blank=True)
     user = models.ForeignKey(CustomUser, on_delete=models.CASCADE)
+    # TASK 1: Summary fields
+    summary = models.TextField(
+        null=True, 
+        blank=True,
+        help_text="Auto-generated summary of the conversation"
+    )
+    summary_generated_at = models.DateTimeField(
+        null=True,
+        blank=True,
+        help_text="Timestamp when summary was generated"
+    )
+    is_summary_stale = models.BooleanField(
+        default=False,
+        help_text="Indicates if summary needs to be regenerated"
+    )
 
+    class Meta:
+        ordering = ['-created_at']
+        indexes = [
+            models.Index(fields=['user', '-created_at']),
+            models.Index(fields=['is_summary_stale']),
+        ]
     def __str__(self):
         return self.title
 
@@ -63,3 +84,197 @@ def save(self, *args, **kwargs):
 
     def __str__(self):
         return f"{self.role}: {self.content[:20]}..."
+
+
+# TASK 3: File Upload Model
+class UploadedFile(models.Model):
+    """
+    Model for storing uploaded files with metadata.
+    TASK 3: File upload with duplicate detection
+    """
+    STATUS_CHOICES = [
+        ('pending', 'Pending'),
+        ('processing', 'Processing'),
+        ('completed', 'Completed'),
+        ('failed', 'Failed'),
+    ]
+
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    user = models.ForeignKey(
+        CustomUser,
+        on_delete=models.CASCADE,
+        related_name='uploaded_files'
+    )
+    conversation = models.ForeignKey(
+        Conversation,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name='files'
+    )
+
+    file = models.FileField(upload_to='uploads/%Y/%m/%d/')
+    filename = models.CharField(max_length=255)
+    file_size = models.BigIntegerField()  # in bytes
+    file_type = models.CharField(max_length=50)  # e.g., 'pdf', 'docx'
+    file_hash = models.CharField(max_length=64, unique=True)  # SHA256
+
+    status = models.CharField(
+        max_length=20,
+        choices=STATUS_CHOICES,
+        default='pending'
+    )
+
+    uploaded_at = models.DateTimeField(auto_now_add=True)
+    processed_at = models.DateTimeField(null=True, blank=True)
+    error_message = models.TextField(null=True, blank=True)
+
+    # Metadata
+    mime_type = models.CharField(max_length=100, null=True, blank=True)
+    page_count = models.IntegerField(null=True, blank=True)  # For PDFs
+    is_indexed = models.BooleanField(default=False)  # For RAG indexing
+
+    class Meta:
+        ordering = ['-uploaded_at']
+        indexes = [
+            models.Index(fields=['user', '-uploaded_at']),
+            models.Index(fields=['file_hash']),
+            models.Index(fields=['status']),
+        ]
+
+    def __str__(self):
+        return f"{self.filename} ({self.user.username})"
+
+    @staticmethod
+    def calculate_file_hash(file_obj):
+        """Calculate SHA256 hash of file"""
+        hash_sha256 = hashlib.sha256()
+        for chunk in file_obj.chunks():
+            hash_sha256.update(chunk)
+        file_obj.seek(0)  # Reset file pointer
+        return hash_sha256.hexdigest()
+
+    def save(self, *args, **kwargs):
+        if self.file and not self.file_hash:
+            self.file_hash = self.calculate_file_hash(self.file)
+        super().save(*args, **kwargs)
+
+
+# TASK 4: Activity Logging Model
+class ActivityLog(models.Model):
+    """
+    Model for logging all user activities.
+    TASK 4: Activity logging and auditing
+    """
+    ACTION_CHOICES = [
+        ('file_upload', 'File Upload'),
+        ('file_delete', 'File Delete'),
+        ('file_access', 'File Access'),
+        ('conversation_create', 'Conversation Create'),
+        ('conversation_delete', 'Conversation Delete'),
+        ('conversation_edit', 'Conversation Edit'),
+        ('message_send', 'Message Send'),
+        ('summary_generate', 'Summary Generate'),
+        ('summary_regenerate', 'Summary Regenerate'),
+    ]
+
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    user = models.ForeignKey(
+        CustomUser,
+        on_delete=models.SET_NULL,
+        null=True,
+        related_name='activity_logs'
+    )
+    action = models.CharField(max_length=50, choices=ACTION_CHOICES)
+    resource_type = models.CharField(max_length=50)  # 'file', 'conversation', etc.
+    resource_id = models.CharField(max_length=100, null=True, blank=True)
+    details = models.JSONField(default=dict, blank=True)  # Extra context
+    ip_address = models.GenericIPAddressField(null=True, blank=True)
+    user_agent = models.TextField(blank=True)
+    status = models.CharField(
+        max_length=20,
+        default='success',
+        choices=[('success', 'Success'), ('failed', 'Failed')]
+    )
+    timestamp = models.DateTimeField(auto_now_add=True, db_index=True)
+
+    class Meta:
+        ordering = ['-timestamp']
+        indexes = [
+            models.Index(fields=['user', '-timestamp']),
+            models.Index(fields=['action', '-timestamp']),
+            models.Index(fields=['resource_type', 'resource_id']),
+        ]
+
+    def __str__(self):
+        return f"{self.user} - {self.action} at {self.timestamp}"
+
+
+# TASK 4: User Role Model for RBAC
+class UserRole(models.Model):
+    """
+    Model for user roles - used for role-based access control.
+    TASK 4: Role-based access control
+    """
+    ROLE_CHOICES = [
+        ('user', 'Regular User'),
+        ('moderator', 'Moderator'),
+        ('admin', 'Administrator'),
+    ]
+
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    user = models.OneToOneField(
+        CustomUser,
+        on_delete=models.CASCADE,
+        related_name='role_profile'
+    )
+    role = models.CharField(
+        max_length=20,
+        choices=ROLE_CHOICES,
+        default='user'
+    )
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    def __str__(self):
+        return f"{self.user.username} - {self.get_role_display()}"
+
+
+# TASK 4: File Permission Model for Granular Control
+class FilePermission(models.Model):
+    """
+    Model for granular file permissions.
+    TASK 4: Role-based access control
+    """
+    PERMISSION_CHOICES = [
+        ('view', 'View'),
+        ('upload', 'Upload'),
+        ('delete', 'Delete'),
+        ('share', 'Share'),
+    ]
+
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    user = models.ForeignKey(
+        CustomUser,
+        on_delete=models.CASCADE,
+        related_name='file_permissions'
+    )
+    file = models.ForeignKey(
+        UploadedFile,
+        on_delete=models.CASCADE,
+        related_name='permissions'
+    )
+    permission = models.CharField(max_length=20, choices=PERMISSION_CHOICES)
+    granted_by = models.ForeignKey(
+        CustomUser,
+        on_delete=models.SET_NULL,
+        null=True,
+        related_name='granted_permissions'
+    )
+    created_at = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        unique_together = ('user', 'file', 'permission')
+
+    def __str__(self):
+        return f"{self.user.username} - {self.permission} on {self.file.filename}"
diff --git a/backend/chat/serializers.py b/backend/chat/serializers.py
index 0c721c061..18cbde33e 100644
--- a/backend/chat/serializers.py
+++ b/backend/chat/serializers.py
@@ -4,6 +4,9 @@
 
 from chat.models import Conversation, Message, Role, Version
 
+# file upload related serializer
+from chat.models import UploadedFile
+
 
 def should_serialize(validated_data, field_name) -> bool:
     if validated_data.get(field_name) is not None:
@@ -150,3 +153,95 @@ def update(self, instance, validated_data):
                 version_serializer.save(conversation=instance)
 
         return instance
+
+
+class ConversationSummarySerializer(serializers.ModelSerializer):
+    message_count = serializers.SerializerMethodField()
+
+    class Meta:
+        model = Conversation
+        fields = [
+            'id',
+            'title',
+            'summary',
+            'summary_generated_at',
+            'is_summary_stale',
+            'message_count',
+            'created_at',
+        ]
+
+    def get_message_count(self, obj):
+        from chat.models import Message
+        return Message.objects.filter(
+            version__conversation=obj
+        ).count()
+
+
+class UploadedFileSerializer(serializers.ModelSerializer):
+    """Serializer for UploadedFile model.
+
+    When a file is provided we calculate its hash and check for duplicates so
+    the same file cannot be uploaded more than once.  Some metadata is also
+    populated automatically (filename, size, type, owner).
+    """
+
+    class Meta:
+        model = UploadedFile
+        # expose all relevant metadata fields so the frontend can render them
+        fields = [
+            "id",
+            "user",
+            "conversation",
+            "file",
+            "filename",
+            "file_size",
+            "file_type",
+            "file_hash",
+            "status",
+            "uploaded_at",
+            "processed_at",
+            "error_message",
+            "mime_type",
+            "page_count",
+            "is_indexed",
+        ]
+        read_only_fields = [
+            "id",
+            "user",
+            "file_hash",
+            "status",
+            "uploaded_at",
+            "processed_at",
+            "error_message",
+            "mime_type",
+            "page_count",
+            "is_indexed",
+        ]
+
+    def validate_file(self, value):
+        """Compute SHA256 of the incoming file and reject duplicates."""
+        # calculate and then rewind pointer so the same file object can still be
+        # saved by Django's storage backend
+        file_hash = UploadedFile.calculate_file_hash(value)
+        value.seek(0)
+        if UploadedFile.objects.filter(file_hash=file_hash).exists():
+            raise serializers.ValidationError("A file with the same content has already been uploaded.")
+        return value
+
+    def create(self, validated_data):
+        # automatically populate some meta fields that the client doesn't need
+        request = self.context.get("request")
+        if request and hasattr(request, "user"):
+            validated_data["user"] = request.user
+
+        file_obj = validated_data.get("file")
+        if file_obj:
+            validated_data["filename"] = file_obj.name
+            validated_data["file_size"] = file_obj.size
+            # simple type extraction based on extension
+            if "." in file_obj.name:
+                validated_data["file_type"] = file_obj.name.rsplit('.', 1)[1]
+            else:
+                validated_data["file_type"] = ""
+
+        return super().create(validated_data)
\ No newline at end of file
diff --git a/backend/chat/signals.py b/backend/chat/signals.py
new file mode 100644
index 000000000..a5e7cc47d
--- /dev/null
+++ b/backend/chat/signals.py
@@ -0,0 +1,31 @@
+from django.db.models.signals import post_save, m2m_changed
+from django.dispatch import receiver
+from django.core.cache import cache
+from chat.models import Conversation, Message
+from chat.summary_service import ConversationSummaryService
+import logging
+    
+logger = logging.getLogger(__name__)
+
+@receiver(post_save, sender=Message)
+def regenerate_summary_on_message_save(sender, instance, created, **kwargs):
+    """Generate summary after new message is added"""
+    if created and instance.conversation:
+        conversation = instance.conversation
+        
+        # Only regenerate if we have enough messages
+        if conversation.messages.count() >= ConversationSummaryService.MIN_MESSAGES_FOR_SUMMARY:
+            ConversationSummaryService.update_conversation_summary(conversation)
+
+@receiver(post_save, sender=Conversation)
+def handle_conversation_save(sender, instance, created, **kwargs):
+    """Handle conversation creation"""
+    if created:
+        logger.info(f"New conversation created: {instance.id}")
+        # Initialize summary as stale so it's generated later
+        instance.is_summary_stale = True
+        Conversation.objects.filter(id=instance.id).update(is_summary_stale=True)
+
+# Connect signals in apps.py
+def ready():
+    import chat.signals
\ No newline at end of file
diff --git a/backend/chat/summary_service.py b/backend/chat/summary_service.py
new file mode 100644
index 000000000..9bff05301
--- /dev/null
+++ b/backend/chat/summary_service.py
@@ -0,0 +1,127 @@
+import logging
+import json
+from typing import Optional
+from datetime import timedelta
+from django.utils.timezone import now
+from django.core.cache import cache
+from src.libs import openai
+
+logger = logging.getLogger(__name__)
+
+class ConversationSummaryService:
+    """Service for generating and managing conversation summaries"""
+    
+    MAX_TOKENS = 200
+    SUMMARY_CACHE_TIMEOUT = 3600  # 1 hour
+    MIN_MESSAGES_FOR_SUMMARY = 3
+    
+    @staticmethod
+    def generate_summary(conversation) -> Optional[str]:
+        """
+        Generate summary for a conversation using OpenAI
+        
+        Args:
+            conversation: Conversation instance
+            
+        Returns:
+            Generated summary string or None
+        """
+        try:
+            # Check if conversation has enough messages
+            message_count = conversation.messages.count()
+            if message_count < ConversationSummaryService.MIN_MESSAGES_FOR_SUMMARY:
+                logger.info(f"Conversation {conversation.id} has insufficient messages for summary")
+                return None
+            
+            # Fetch all messages for context
+            messages = conversation.messages.all().order_by('created_at')
+            
+            # Build context from messages
+            context = "\n".join([
+                f"{'User' if msg.role.name == 'user' else 'Assistant'}: {msg.content[:200]}"
+                for msg in messages[:10]  # Limit to last 10 messages
+            ])
+            
+            # Call OpenAI API
+            response = openai.ChatCompletion.create(
+                engine="gpt-35-turbo",  # Azure deployment name
+                messages=[
+                    {
+                        "role": "system",
+                        "content": "Provide a concise 2-3 sentence summary of the conversation."
+                    },
+                    {
+                        "role": "user",
+                        "content": f"Conversation to summarize:\n\n{context}"
+                    }
+                ],
+                max_tokens=ConversationSummaryService.MAX_TOKENS,
+                temperature=0.3
+            )
+            
+            summary = response['choices'][0]['message']['content'].strip()
+            logger.info(f"Successfully generated summary for conversation {conversation.id}")
+            return summary
+            
+        except openai.error.OpenAIError as e:
+            logger.error(f"OpenAI API error while generating summary: {str(e)}")
+            return None
+        except Exception as e:
+            logger.error(f"Unexpected error in summary generation: {str(e)}")
+            return None
+    
+    @staticmethod
+    def update_conversation_summary(conversation) -> bool:
+        """
+        Update conversation with generated summary
+        
+        Args:
+            conversation: Conversation instance
+            
+        Returns:
+            True if successful, False otherwise
+        """
+        try:
+            summary = ConversationSummaryService.generate_summary(conversation)
+            
+            if summary:
+                conversation.summary = summary
+                conversation.summary_generated_at = now()
+                conversation.is_summary_stale = False
+                conversation.save(update_fields=['summary', 'summary_generated_at', 'is_summary_stale'])
+                
+                # Cache the summary
+                cache.set(
+                    f"conversation_summary_{conversation.id}",
+                    summary,
+                    ConversationSummaryService.SUMMARY_CACHE_TIMEOUT
+                )
+                return True
+            return False
+            
+        except Exception as e:
+            logger.error(f"Error updating conversation summary: {str(e)}")
+            return False
+    
+    @staticmethod
+    def get_cached_summary(conversation) -> Optional[str]:
+        """Retrieve summary from cache or database"""
+        cache_key = f"conversation_summary_{conversation.id}"
+        cached = cache.get(cache_key)
+        
+        if cached:
+            return cached
+        
+        if conversation.summary:
+            cache.set(cache_key, conversation.summary, 
+                     ConversationSummaryService.SUMMARY_CACHE_TIMEOUT)
+            return conversation.summary
+        
+        return None
+    
+    @staticmethod
+    def mark_summary_stale(conversation):
+        """Mark summary as needing regeneration (e.g., when conversation is edited)"""
+        conversation.is_summary_stale = True
+        conversation.save(update_fields=['is_summary_stale'])
+        cache.delete(f"conversation_summary_{conversation.id}")
\ No newline at end of file
diff --git a/backend/chat/tasks.py b/backend/chat/tasks.py
new file mode 100644
index 000000000..a6dad590f
--- /dev/null
+++ b/backend/chat/tasks.py
@@ -0,0 +1,45 @@
+from celery import shared_task
+from django.utils.timezone import now
+from datetime import timedelta
+from chat.models import Conversation
+from chat.summary_service import ConversationSummaryService
+import logging
+
+logger = logging.getLogger(__name__)
+
+@shared_task(name='chat.tasks.cleanup_old_conversations')
+def cleanup_old_conversations(days=30):
+    """Clean up conversations older than specified days"""
+    cutoff_date = now() - timedelta(days=days)
+    deleted_count, _ = Conversation.objects.filter(
+        created_at__lt=cutoff_date
+    ).delete()
+    
+    logger.info(f"Cleanup task: Deleted {deleted_count} conversations")
+    return {'deleted': deleted_count}
+
+@shared_task(name='chat.tasks.generate_missing_summaries')
+def generate_missing_summaries():
+    """Generate summaries for conversations that don't have one"""
+    conversations = Conversation.objects.filter(
+        summary__isnull=True,
+        messages__isnull=False
+    ).distinct()[:50]  # Limit to prevent overload
+    
+    count = 0
+    for conversation in conversations:
+        if ConversationSummaryService.update_conversation_summary(conversation):
+            count += 1
+    
+    logger.info(f"Generated summaries for {count} conversations")
+    return {'generated': count}
+
+@shared_task(name='chat.tasks.generate_conversation_summary_task')
+def generate_conversation_summary_task(conversation_id):
+    """Generate summary for a specific conversation"""
+    try:
+        conversation = Conversation.objects.get(id=conversation_id)
+        return ConversationSummaryService.update_conversation_summary(conversation)
+    except Conversation.DoesNotExist:
+        logger.error(f"Conversation {conversation_id} not found")
+        return False
\ No newline at end of file
diff --git a/backend/chat/urls.py b/backend/chat/urls.py
index bd8ceadc0..0bc207cd2 100644
--- a/backend/chat/urls.py
+++ b/backend/chat/urls.py
@@ -1,7 +1,9 @@
 from django.urls import path
+from rest_framework.routers import DefaultRouter
 
 from chat import views
 
+
 urlpatterns = [
     path("", views.chat_root_view, name="chat_root_view"),
     path("conversations/", views.get_conversations, name="get_conversations"),
@@ -20,3 +22,12 @@
     path("conversations/<uuid:pk>/delete/", views.conversation_soft_delete, name="conversation_delete"),
     path("versions/<uuid:pk>/add_message/", views.version_add_message, name="version_add_message"),
 ]
+
+# router for viewsets (summaries, file uploads)
+router = DefaultRouter()
+router.register(r"summaries", views.ConversationSummaryViewSet, basename="conversation-summary")
+router.register(r"files", views.UploadedFileViewSet, basename="uploadedfile")
+
+# append router-generated urls at the end so they don't conflict with the custom
+# function-based endpoints defined above
+urlpatterns += router.urls
diff --git a/backend/chat/views.py b/backend/chat/views.py
index 0d18f7a69..2d63ec004 100644
--- a/backend/chat/views.py
+++ b/backend/chat/views.py
@@ -4,10 +4,19 @@
 from rest_framework.decorators import api_view
 from rest_framework.response import Response
 
-from chat.models import Conversation, Message, Version
+from chat.models import Conversation, Message, Version, UploadedFile
 from chat.serializers import ConversationSerializer, MessageSerializer, TitleSerializer, VersionSerializer
 from chat.utils.branching import make_branched_conversation
+from rest_framework.pagination import PageNumberPagination
+from rest_framework import viewsets, permissions
+from django.db.models import Q
+from .models import Conversation
+from .serializers import ConversationSummarySerializer, UploadedFileSerializer
 
+class StandardPagination(PageNumberPagination):
+    page_size = 10
+    page_size_query_param = "page_size"
+    max_page_size = 100
 
 @api_view(["GET"])
 def chat_root_view(request):
@@ -230,3 +239,68 @@ def version_add_message(request, pk):
             status=status.HTTP_201_CREATED,
         )
     return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
+
+
+
+class ConversationSummaryViewSet(viewsets.ReadOnlyModelViewSet):
+    serializer_class = ConversationSummarySerializer
+    permission_classes = [permissions.IsAuthenticated]
+    pagination_class = StandardPagination
+
+    def get_queryset(self):
+        queryset = Conversation.objects.filter(
+            user=self.request.user
+        )
+
+        has_summary = self.request.query_params.get("has_summary")
+        if has_summary == "true":
+            queryset = queryset.filter(summary__isnull=False)
+        elif has_summary == "false":
+            queryset = queryset.filter(summary__isnull=True)
+
+        is_stale = self.request.query_params.get("is_stale")
+        if is_stale == "true":
+            queryset = queryset.filter(is_summary_stale=True)
+        elif is_stale == "false":
+            queryset = queryset.filter(is_summary_stale=False)
+
+        search = self.request.query_params.get("search")
+        if search:
+            queryset = queryset.filter(
+                Q(title__icontains=search) |
+                Q(summary__icontains=search)
+            )
+
+        return queryset.order_by("-created_at")
+
+
+class UploadedFileViewSet(viewsets.ModelViewSet):
+    """CRUD operations for user-uploaded files.
+
+    * POST /files/          -> upload new file with duplicate prevention
+    * GET  /files/          -> list user's files (pagination supported)
+    * GET  /files/{pk}/     -> retrieve metadata for a single file
+    * DELETE /files/{pk}/   -> delete file record and remove file from storage
+    """
+
+    serializer_class = UploadedFileSerializer
+    permission_classes = [permissions.IsAuthenticated]
+    pagination_class = StandardPagination
+
+    def get_queryset(self):
+        qs = UploadedFile.objects.filter(user=self.request.user)
+        # optional filtering by conversation
+        conv = self.request.query_params.get("conversation_id")
+        if conv:
+            qs = qs.filter(conversation__id=conv)
+        return qs.order_by("-uploaded_at")
+
+    def perform_create(self, serializer):
+        # the serializer's create() method will attach the user and metadata
+        serializer.save()
+
+    def destroy(self, request, *args, **kwargs):
+        # remove the actual file from disk/storage before deleting the DB record
+        instance = self.get_object()
+        instance.file.delete(save=False)
+        return super().destroy(request, *args, **kwargs)
\ No newline at end of file
diff --git a/backend/requirements.txt b/backend/requirements.txt
new file mode 100644
index 000000000..cdddc9863
--- /dev/null
+++ b/backend/requirements.txt
@@ -0,0 +1,79 @@
+# =========================
+# Core Django & REST
+# =========================
+Django==4.2.7
+djangorestframework==3.14.0
+django-cors-headers==4.3.1
+django-filter==23.4
+django-extensions==3.2.3
+
+# =========================
+# Database (PostgreSQL)
+# =========================
+psycopg2-binary==2.9.9
+
+# =========================
+# Caching & Background Tasks
+# =========================
+redis==5.0.1
+django-redis==5.4.0
+celery==5.3.4
+django-celery-beat==2.5.0
+django-celery-results==2.5.1
+
+# =========================
+# Authentication & API Docs
+# =========================
+djangorestframework-simplejwt==5.4.0
+drf-spectacular==0.26.5
+PyJWT==2.8.1
+
+# =========================
+# File Handling
+# =========================
+pillow==10.1.0
+
+# =========================
+# AI / Summary Generation
+# =========================
+openai==0.27.8
+
+# =========================
+# Utilities
+# =========================
+python-dotenv==1.0.0
+python-decouple==3.8
+python-dateutil==2.8.2
+requests==2.31.0
+
+# =========================
+# Logging & Monitoring
+# =========================
+sentry-sdk==1.38.0
+
+# =========================
+# Security
+# =========================
+cryptography==41.0.7
+
+# =========================
+# Testing
+# =========================
+pytest==7.4.3
+pytest-django==4.7.0
+pytest-cov==4.1.0
+factory-boy==3.3.0
+faker==21.0.0
+
+# =========================
+# Code Quality
+# =========================
+black==23.12.0
+flake8==6.1.0
+isort==5.13.2
+
+# =========================
+# Production Server
+# =========================
+gunicorn==21.2.0
+uvicorn==0.24.0
\ No newline at end of file