diff --git a/rbox/billing/models.py b/rbox/billing/models.py
index 264f7b6..926430a 100644
--- a/rbox/billing/models.py
+++ b/rbox/billing/models.py
@@ -38,16 +38,17 @@ class UserSubscription(models.Model):
 class UsageRecord(models.Model):
     id = fields.BigIntField(pk=True)
     user = fields.ForeignKeyField("models.User", related_name="usage_records")
-    record_type = fields.CharField(max_length=50)
+    record_type = fields.CharField(max_length=50, index=True)
     amount_bytes = fields.BigIntField()
     resource_type = fields.CharField(max_length=50, null=True)
     resource_id = fields.IntField(null=True)
-    timestamp = fields.DatetimeField(auto_now_add=True)
+    timestamp = fields.DatetimeField(auto_now_add=True, index=True)
     idempotency_key = fields.CharField(max_length=255, unique=True, null=True)
     metadata = fields.JSONField(null=True)
 
     class Meta:
         table = "usage_records"
+        indexes = [("user_id", "record_type", "timestamp")]
 
 class UsageAggregate(models.Model):
     id = fields.IntField(pk=True)
@@ -68,21 +69,22 @@ class Invoice(models.Model):
     user = fields.ForeignKeyField("models.User", related_name="invoices")
     invoice_number = fields.CharField(max_length=50, unique=True)
     stripe_invoice_id = fields.CharField(max_length=255, unique=True, null=True)
-    period_start = fields.DateField()
+    period_start = fields.DateField(index=True)
     period_end = fields.DateField()
     subtotal = fields.DecimalField(max_digits=10, decimal_places=4)
     tax = fields.DecimalField(max_digits=10, decimal_places=4, default=0)
     total = fields.DecimalField(max_digits=10, decimal_places=4)
     currency = fields.CharField(max_length=3, default="USD")
-    status = fields.CharField(max_length=50, default="draft")
+    status = fields.CharField(max_length=50, default="draft", index=True)
     due_date = fields.DateField(null=True)
     paid_at = fields.DatetimeField(null=True)
-    created_at = fields.DatetimeField(auto_now_add=True)
+    created_at = fields.DatetimeField(auto_now_add=True, index=True)
     updated_at = fields.DatetimeField(auto_now=True)
     metadata = fields.JSONField(null=True)
 
     class Meta:
         table = "invoices"
+        indexes = [("user_id", "status", "created_at")]
 
 class InvoiceLineItem(models.Model):
     id = fields.IntField(pk=True)
diff --git a/rbox/billing/stripe_client.py b/rbox/billing/stripe_client.py
index 1e9211c..6c98f86 100644
--- a/rbox/billing/stripe_client.py
+++ b/rbox/billing/stripe_client.py
@@ -3,11 +3,17 @@ from decimal import Decimal
 from typing import Optional, Dict, Any
 from ..settings import settings
 
-stripe.api_key = settings.STRIPE_SECRET_KEY if hasattr(settings, 'STRIPE_SECRET_KEY') else ""
-
 class StripeClient:
     @staticmethod
+    def _ensure_api_key():
+        if not stripe.api_key:
+            if settings.STRIPE_SECRET_KEY:
+                stripe.api_key = settings.STRIPE_SECRET_KEY
+            else:
+                raise ValueError("Stripe API key not configured")
+    @staticmethod
     async def create_customer(email: str, name: str, metadata: Dict = None) -> str:
+        StripeClient._ensure_api_key()
         customer = stripe.Customer.create(
             email=email,
             name=name,
@@ -22,6 +28,7 @@ class StripeClient:
         customer_id: str = None,
         metadata: Dict = None
     ) -> stripe.PaymentIntent:
+        StripeClient._ensure_api_key()
         return stripe.PaymentIntent.create(
             amount=amount,
             currency=currency,
@@ -37,6 +44,7 @@ class StripeClient:
         line_items: list,
         metadata: Dict = None
     ) -> stripe.Invoice:
+        StripeClient._ensure_api_key()
         for item in line_items:
             stripe.InvoiceItem.create(
                 customer=customer_id,
@@ -58,10 +66,12 @@ class StripeClient:
 
     @staticmethod
     async def finalize_invoice(invoice_id: str) -> stripe.Invoice:
+        StripeClient._ensure_api_key()
         return stripe.Invoice.finalize_invoice(invoice_id)
 
     @staticmethod
     async def pay_invoice(invoice_id: str) -> stripe.Invoice:
+        StripeClient._ensure_api_key()
         return stripe.Invoice.pay(invoice_id)
 
     @staticmethod
@@ -69,6 +79,7 @@ class StripeClient:
         payment_method_id: str,
         customer_id: str
     ) -> stripe.PaymentMethod:
+        StripeClient._ensure_api_key()
         payment_method = stripe.PaymentMethod.attach(
             payment_method_id,
             customer=customer_id
@@ -83,6 +94,7 @@ class StripeClient:
 
     @staticmethod
     async def list_payment_methods(customer_id: str, type: str = "card"):
+        StripeClient._ensure_api_key()
         return stripe.PaymentMethod.list(
             customer=customer_id,
             type=type
@@ -94,6 +106,7 @@ class StripeClient:
         price_id: str,
         metadata: Dict = None
     ) -> stripe.Subscription:
+        StripeClient._ensure_api_key()
         return stripe.Subscription.create(
             customer=customer_id,
             items=[{'price': price_id}],
@@ -102,4 +115,5 @@ class StripeClient:
 
     @staticmethod
     async def cancel_subscription(subscription_id: str) -> stripe.Subscription:
+        StripeClient._ensure_api_key()
         return stripe.Subscription.delete(subscription_id)
diff --git a/rbox/billing/usage_tracker.py b/rbox/billing/usage_tracker.py
index 4e57b28..598c57f 100644
--- a/rbox/billing/usage_tracker.py
+++ b/rbox/billing/usage_tracker.py
@@ -108,15 +108,22 @@ class UsageTracker:
     @staticmethod
     async def get_current_storage(user: User) -> int:
         from ..models import File
-        files = await File.filter(user=user, is_deleted=False).all()
+        files = await File.filter(owner=user, is_deleted=False).all()
         return sum(f.size for f in files)
 
     @staticmethod
     async def get_monthly_usage(user: User, year: int, month: int) -> dict:
+        from datetime import date
+        from calendar import monthrange
+
+        start_date = date(year, month, 1)
+        _, last_day = monthrange(year, month)
+        end_date = date(year, month, last_day)
+
         aggregates = await UsageAggregate.filter(
             user=user,
-            date__year=year,
-            date__month=month
+            date__gte=start_date,
+            date__lte=end_date
         ).all()
 
         if not aggregates:
diff --git a/rbox/routers/auth.py b/rbox/routers/auth.py
index 4cbc2f9..90c0025 100644
--- a/rbox/routers/auth.py
+++ b/rbox/routers/auth.py
@@ -2,10 +2,9 @@ from datetime import timedelta
 from typing import Optional, List
 
 from fastapi import APIRouter, Depends, HTTPException, status
-from fastapi.security import OAuth2PasswordRequestForm
 from pydantic import BaseModel
 
-from ..auth import authenticate_user, create_access_token, get_password_hash, get_current_user, get_current_verified_user
+from ..auth import authenticate_user, create_access_token, get_password_hash, get_current_user, get_current_verified_user, verify_password
 from ..models import User
 from ..schemas import Token, UserCreate, TokenData, UserLoginWith2FA
 from ..two_factor import (
@@ -19,6 +18,10 @@ router = APIRouter(
     tags=["auth"],
 )
 
+class LoginRequest(BaseModel):
+    username: str
+    password: str
+
 class TwoFactorLogin(BaseModel):
     username: str
     password: str
@@ -65,8 +68,8 @@ async def register_user(user_in: UserCreate):
     return {"access_token": access_token, "token_type": "bearer"}
 
 @router.post("/token", response_model=Token)
-async def login_for_access_token(form_data: OAuth2PasswordRequestForm = Depends()):
-    auth_result = await authenticate_user(form_data.username, form_data.password, None)
+async def login_for_access_token(login_data: LoginRequest):
+    auth_result = await authenticate_user(login_data.username, login_data.password, None)
 
     if not auth_result:
         raise HTTPException(
@@ -83,7 +86,7 @@ async def login_for_access_token(form_data: OAuth2PasswordRequestForm = Depends(
             headers={"X-2FA-Required": "true"},
         )
 
-    access_token_expires = timedelta(minutes=30) # Use settings
+    access_token_expires = timedelta(minutes=30)
     access_token = create_access_token(
         data={"sub": user.username}, expires_delta=access_token_expires, two_factor_verified=True
     )
diff --git a/rbox/routers/billing.py b/rbox/routers/billing.py
index 45e5551..9a4f102 100644
--- a/rbox/routers/billing.py
+++ b/rbox/routers/billing.py
@@ -52,25 +52,28 @@ class SubscriptionResponse(BaseModel):
 
 @router.get("/usage/current")
 async def get_current_usage(current_user: User = Depends(get_current_user)):
-    storage_bytes = await UsageTracker.get_current_storage(current_user)
-    today = date.today()
+    try:
+        storage_bytes = await UsageTracker.get_current_storage(current_user)
+        today = date.today()
 
-    usage_today = await UsageAggregate.get_or_none(user=current_user, date=today)
+        usage_today = await UsageAggregate.get_or_none(user=current_user, date=today)
+
+        if usage_today:
+            return {
+                "storage_gb": round(storage_bytes / (1024**3), 4),
+                "bandwidth_down_gb_today": round(usage_today.bandwidth_down_bytes / (1024**3), 4),
+                "bandwidth_up_gb_today": round(usage_today.bandwidth_up_bytes / (1024**3), 4),
+                "as_of": today.isoformat()
+            }
 
-    if usage_today:
         return {
             "storage_gb": round(storage_bytes / (1024**3), 4),
-            "bandwidth_down_gb_today": round(usage_today.bandwidth_down_bytes / (1024**3), 4),
-            "bandwidth_up_gb_today": round(usage_today.bandwidth_up_bytes / (1024**3), 4),
+            "bandwidth_down_gb_today": 0,
+            "bandwidth_up_gb_today": 0,
             "as_of": today.isoformat()
         }
-
-    return {
-        "storage_gb": round(storage_bytes / (1024**3), 4),
-        "bandwidth_down_gb_today": 0,
-        "bandwidth_up_gb_today": 0,
-        "as_of": today.isoformat()
-    }
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Failed to fetch usage data: {str(e)}")
 
 @router.get("/usage/monthly")
 async def get_monthly_usage(
@@ -78,17 +81,27 @@ async def get_monthly_usage(
     month: Optional[int] = None,
     current_user: User = Depends(get_current_user)
 ) -> UsageResponse:
-    if year is None or month is None:
-        now = datetime.now()
-        year = now.year
-        month = now.month
+    try:
+        if year is None or month is None:
+            now = datetime.now()
+            year = now.year
+            month = now.month
 
-    usage = await UsageTracker.get_monthly_usage(current_user, year, month)
+        if not (1 <= month <= 12):
+            raise HTTPException(status_code=400, detail="Month must be between 1 and 12")
+        if not (2020 <= year <= 2100):
+            raise HTTPException(status_code=400, detail="Year must be between 2020 and 2100")
 
-    return UsageResponse(
-        **usage,
-        period=f"{year}-{month:02d}"
-    )
+        usage = await UsageTracker.get_monthly_usage(current_user, year, month)
+
+        return UsageResponse(
+            **usage,
+            period=f"{year}-{month:02d}"
+        )
+    except HTTPException:
+        raise
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Failed to fetch monthly usage: {str(e)}")
 
 @router.get("/invoices")
 async def list_invoices(
@@ -96,35 +109,45 @@ async def list_invoices(
     offset: int = 0,
     current_user: User = Depends(get_current_user)
 ) -> List[InvoiceResponse]:
-    invoices = await Invoice.filter(user=current_user).order_by("-created_at").offset(offset).limit(limit).all()
+    try:
+        if limit < 1 or limit > 100:
+            raise HTTPException(status_code=400, detail="Limit must be between 1 and 100")
+        if offset < 0:
+            raise HTTPException(status_code=400, detail="Offset must be non-negative")
 
-    result = []
-    for invoice in invoices:
-        line_items = await invoice.line_items.all()
-        result.append(InvoiceResponse(
-            id=invoice.id,
-            invoice_number=invoice.invoice_number,
-            period_start=invoice.period_start,
-            period_end=invoice.period_end,
-            subtotal=float(invoice.subtotal),
-            tax=float(invoice.tax),
-            total=float(invoice.total),
-            status=invoice.status,
-            due_date=invoice.due_date,
-            paid_at=invoice.paid_at,
-            line_items=[
-                {
-                    "description": item.description,
-                    "quantity": float(item.quantity),
-                    "unit_price": float(item.unit_price),
-                    "amount": float(item.amount),
-                    "type": item.item_type
-                }
-                for item in line_items
-            ]
-        ))
+        invoices = await Invoice.filter(user=current_user).order_by("-created_at").offset(offset).limit(limit).all()
 
-    return result
+        result = []
+        for invoice in invoices:
+            line_items = await invoice.line_items.all()
+            result.append(InvoiceResponse(
+                id=invoice.id,
+                invoice_number=invoice.invoice_number,
+                period_start=invoice.period_start,
+                period_end=invoice.period_end,
+                subtotal=float(invoice.subtotal),
+                tax=float(invoice.tax),
+                total=float(invoice.total),
+                status=invoice.status,
+                due_date=invoice.due_date,
+                paid_at=invoice.paid_at,
+                line_items=[
+                    {
+                        "description": item.description,
+                        "quantity": float(item.quantity),
+                        "unit_price": float(item.unit_price),
+                        "amount": float(item.amount),
+                        "type": item.item_type
+                    }
+                    for item in line_items
+                ]
+            ))
+
+        return result
+    except HTTPException:
+        raise
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Failed to fetch invoices: {str(e)}")
 
 @router.get("/invoices/{invoice_id}")
 async def get_invoice(
@@ -187,36 +210,46 @@ async def get_subscription(current_user: User = Depends(get_current_user)) -> Su
 
 @router.post("/payment-methods/setup-intent")
 async def create_setup_intent(current_user: User = Depends(get_current_user)):
-    subscription = await UserSubscription.get_or_none(user=current_user)
+    try:
+        from ..settings import settings
+        if not settings.STRIPE_SECRET_KEY:
+            raise HTTPException(status_code=503, detail="Payment processing not configured")
 
-    if not subscription or not subscription.stripe_customer_id:
-        customer_id = await StripeClient.create_customer(
-            email=current_user.email,
-            name=current_user.username,
-            metadata={"user_id": str(current_user.id)}
+        subscription = await UserSubscription.get_or_none(user=current_user)
+
+        if not subscription or not subscription.stripe_customer_id:
+            customer_id = await StripeClient.create_customer(
+                email=current_user.email,
+                name=current_user.username,
+                metadata={"user_id": str(current_user.id)}
+            )
+
+            if not subscription:
+                subscription = await UserSubscription.create(
+                    user=current_user,
+                    billing_type="pay_as_you_go",
+                    stripe_customer_id=customer_id,
+                    status="active"
+                )
+            else:
+                subscription.stripe_customer_id = customer_id
+                await subscription.save()
+
+        import stripe
+        StripeClient._ensure_api_key()
+        setup_intent = stripe.SetupIntent.create(
+            customer=subscription.stripe_customer_id,
+            payment_method_types=["card"]
         )
 
-        if not subscription:
-            subscription = await UserSubscription.create(
-                user=current_user,
-                billing_type="pay_as_you_go",
-                stripe_customer_id=customer_id,
-                status="active"
-            )
-        else:
-            subscription.stripe_customer_id = customer_id
-            await subscription.save()
-
-    import stripe
-    setup_intent = stripe.SetupIntent.create(
-        customer=subscription.stripe_customer_id,
-        payment_method_types=["card"]
-    )
-
-    return {
-        "client_secret": setup_intent.client_secret,
-        "customer_id": subscription.stripe_customer_id
-    }
+        return {
+            "client_secret": setup_intent.client_secret,
+            "customer_id": subscription.stripe_customer_id
+        }
+    except HTTPException:
+        raise
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Failed to create setup intent: {str(e)}")
 
 @router.get("/payment-methods")
 async def list_payment_methods(current_user: User = Depends(get_current_user)):
@@ -238,49 +271,71 @@ async def list_payment_methods(current_user: User = Depends(get_current_user)):
 async def stripe_webhook(request: Request):
     import stripe
     from ..settings import settings
-
-    payload = await request.body()
-    sig_header = request.headers.get("stripe-signature")
+    from ..billing.models import BillingEvent
 
     try:
-        event = stripe.Webhook.construct_event(
-            payload, sig_header, settings.STRIPE_WEBHOOK_SECRET
-        )
-    except ValueError:
-        raise HTTPException(status_code=400, detail="Invalid payload")
-    except stripe.error.SignatureVerificationError:
-        raise HTTPException(status_code=400, detail="Invalid signature")
+        payload = await request.body()
+        sig_header = request.headers.get("stripe-signature")
 
-    if event["type"] == "invoice.payment_succeeded":
-        invoice_data = event["data"]["object"]
-        rbox_invoice_id = invoice_data.get("metadata", {}).get("rbox_invoice_id")
+        if not settings.STRIPE_WEBHOOK_SECRET:
+            raise HTTPException(status_code=503, detail="Webhook secret not configured")
 
-        if rbox_invoice_id:
-            invoice = await Invoice.get_or_none(id=int(rbox_invoice_id))
-            if invoice:
-                await InvoiceGenerator.mark_invoice_paid(invoice)
-
-    elif event["type"] == "invoice.payment_failed":
-        pass
-
-    elif event["type"] == "payment_method.attached":
-        payment_method = event["data"]["object"]
-        customer_id = payment_method["customer"]
-
-        subscription = await UserSubscription.get_or_none(stripe_customer_id=customer_id)
-        if subscription:
-            await PaymentMethod.create(
-                user=subscription.user,
-                stripe_payment_method_id=payment_method["id"],
-                type=payment_method["type"],
-                last4=payment_method.get("card", {}).get("last4"),
-                brand=payment_method.get("card", {}).get("brand"),
-                exp_month=payment_method.get("card", {}).get("exp_month"),
-                exp_year=payment_method.get("card", {}).get("exp_year"),
-                is_default=True
+        try:
+            event = stripe.Webhook.construct_event(
+                payload, sig_header, settings.STRIPE_WEBHOOK_SECRET
             )
+        except ValueError as e:
+            raise HTTPException(status_code=400, detail=f"Invalid payload: {str(e)}")
+        except stripe.error.SignatureVerificationError as e:
+            raise HTTPException(status_code=400, detail=f"Invalid signature: {str(e)}")
 
-    return JSONResponse(content={"status": "success"})
+        event_id = event.get("id")
+        existing_event = await BillingEvent.get_or_none(stripe_event_id=event_id)
+        if existing_event:
+            return JSONResponse(content={"status": "already_processed"})
+
+        await BillingEvent.create(
+            event_type=event["type"],
+            stripe_event_id=event_id,
+            data=event["data"],
+            processed=False
+        )
+
+        if event["type"] == "invoice.payment_succeeded":
+            invoice_data = event["data"]["object"]
+            rbox_invoice_id = invoice_data.get("metadata", {}).get("rbox_invoice_id")
+
+            if rbox_invoice_id:
+                invoice = await Invoice.get_or_none(id=int(rbox_invoice_id))
+                if invoice:
+                    await InvoiceGenerator.mark_invoice_paid(invoice)
+
+        elif event["type"] == "invoice.payment_failed":
+            pass
+
+        elif event["type"] == "payment_method.attached":
+            payment_method = event["data"]["object"]
+            customer_id = payment_method["customer"]
+
+            subscription = await UserSubscription.get_or_none(stripe_customer_id=customer_id)
+            if subscription:
+                await PaymentMethod.create(
+                    user=subscription.user,
+                    stripe_payment_method_id=payment_method["id"],
+                    type=payment_method["type"],
+                    last4=payment_method.get("card", {}).get("last4"),
+                    brand=payment_method.get("card", {}).get("brand"),
+                    exp_month=payment_method.get("card", {}).get("exp_month"),
+                    exp_year=payment_method.get("card", {}).get("exp_year"),
+                    is_default=True
+                )
+
+        await BillingEvent.filter(stripe_event_id=event_id).update(processed=True)
+        return JSONResponse(content={"status": "success"})
+    except HTTPException:
+        raise
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Webhook processing failed: {str(e)}")
 
 @router.get("/pricing")
 async def get_pricing():
@@ -310,3 +365,10 @@ async def list_plans():
         }
         for plan in plans
     ]
+
+@router.get("/stripe-key")
+async def get_stripe_key():
+    from ..settings import settings
+    if not settings.STRIPE_PUBLISHABLE_KEY:
+        raise HTTPException(status_code=503, detail="Payment processing not configured")
+    return {"publishable_key": settings.STRIPE_PUBLISHABLE_KEY}
diff --git a/static/css/billing.css b/static/css/billing.css
index 0bd9e0d..089a354 100644
--- a/static/css/billing.css
+++ b/static/css/billing.css
@@ -369,3 +369,33 @@
     border-radius: 4px;
     font-size: 1rem;
 }
+
+.loading {
+    text-align: center;
+    padding: 3rem;
+    font-size: 1.2rem;
+    color: #6b7280;
+}
+
+.error-message {
+    background: #fee2e2;
+    border: 1px solid #ef4444;
+    color: #991b1b;
+    padding: 1rem;
+    border-radius: 8px;
+    margin: 1rem 0;
+}
+
+.modal-actions {
+    display: flex;
+    gap: 1rem;
+    margin-top: 1.5rem;
+    justify-content: flex-end;
+}
+
+#payment-element {
+    margin: 1.5rem 0;
+    padding: 1rem;
+    border: 1px solid #e5e7eb;
+    border-radius: 8px;
+}
diff --git a/static/css/code-editor-view.css b/static/css/code-editor-view.css
index 23ebb75..c9ccb3d 100644
--- a/static/css/code-editor-view.css
+++ b/static/css/code-editor-view.css
@@ -1,13 +1,25 @@
-.code-editor-view {
-    position: absolute;
+.code-editor-overlay {
+    position: fixed;
     top: 0;
     left: 0;
     width: 100%;
     height: 100%;
+    background: rgba(0, 0, 0, 0.5);
+    z-index: 1000;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+}
+
+.code-editor-container {
+    width: 90%;
+    height: 90%;
+    max-width: 1400px;
+    background: white;
+    border-radius: 8px;
     display: flex;
     flex-direction: column;
-    background: white;
-    z-index: 100;
+    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
 }
 
 .code-editor-header {
@@ -49,6 +61,16 @@
     font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
     font-size: 14px;
     background: white;
+    user-select: text !important;
+    cursor: text;
+}
+
+.code-editor-body .CodeMirror * {
+    user-select: text !important;
+}
+
+.code-editor-body .CodeMirror-scroll {
+    cursor: text;
 }
 
 .code-editor-body .CodeMirror-gutters {
diff --git a/static/index.html b/static/index.html
index 819cd14..41e895a 100644
--- a/static/index.html
+++ b/static/index.html
@@ -10,6 +10,7 @@
     <link rel="stylesheet" href="/static/css/code-editor-view.css">
     <link rel="stylesheet" href="/static/css/file-upload-view.css">
     <link rel="manifest" href="/static/manifest.json">
+    <script src="https://js.stripe.com/v3/"></script>
     <script src="/static/lib/codemirror/codemirror.min.js"></script>
     <script src="/static/lib/codemirror/javascript.min.js"></script>
     <script src="/static/lib/codemirror/python.min.js"></script>
diff --git a/static/js/api-contract.js b/static/js/api-contract.js
new file mode 100644
index 0000000..5bfa975
--- /dev/null
+++ b/static/js/api-contract.js
@@ -0,0 +1,42 @@
+export default class APIContract {
+    static validateResponse(response, schema, logger = null) {
+        const errors = [];
+
+        for (const [field, expectedType] of Object.entries(schema)) {
+            if (!(field in response)) {
+                errors.push(`Missing required field: ${field}`);
+            } else {
+                const actualType = typeof response[field];
+                if (actualType !== expectedType) {
+                    errors.push(
+                        `Field '${field}' type mismatch: expected ${expectedType}, got ${actualType}`
+                    );
+                }
+            }
+        }
+
+        if (errors.length > 0) {
+            const message = `API Contract Violation:\n${errors.join('\n')}`;
+            logger?.error(message);
+            throw new Error(message);
+        }
+
+        return response;
+    }
+
+    static validateArray(array, itemSchema, logger = null) {
+        if (!Array.isArray(array)) {
+            logger?.error('Expected array but got non-array');
+            throw new Error('Expected array response');
+        }
+
+        return array.map((item, index) => {
+            try {
+                return this.validateResponse(item, itemSchema, logger);
+            } catch (error) {
+                logger?.error(`Array item ${index} validation failed`, error);
+                throw error;
+            }
+        });
+    }
+}
diff --git a/static/js/api.js b/static/js/api.js
index 5ef4022..b31a7b7 100644
--- a/static/js/api.js
+++ b/static/js/api.js
@@ -1,7 +1,11 @@
 class APIClient {
-    constructor(baseURL = '/') {
+    constructor(baseURL = '/', logger = null, perfMonitor = null, appState = null) {
         this.baseURL = baseURL;
         this.token = localStorage.getItem('token');
+        this.logger = logger;
+        this.perfMonitor = perfMonitor;
+        this.appState = appState;
+        this.activeRequests = 0;
     }
 
     setToken(token) {
@@ -18,76 +22,147 @@ class APIClient {
     }
 
     async request(endpoint, options = {}) {
+        this.activeRequests++;
+        this.appState?.setState({ isLoading: true });
+
+        const startTime = performance.now();
         const url = `${this.baseURL}${endpoint}`;
-        const headers = {
-            ...options.headers,
-        };
+        const method = options.method || 'GET';
 
-        if (this.token && !options.skipAuth) {
-            headers['Authorization'] = `Bearer ${this.token}`;
-        }
+        try {
+            this.logger?.debug(`API ${method}: ${endpoint}`);
 
-        if (!(options.body instanceof FormData) && options.body) {
-            headers['Content-Type'] = 'application/json';
-        }
+            const headers = {
+                ...options.headers,
+            };
 
-        const config = {
-            ...options,
-            headers,
-        };
-
-        if (config.body && !(config.body instanceof FormData)) {
-            config.body = JSON.stringify(config.body);
-        }
-
-        const response = await fetch(url, config);
-
-        if (response.status === 401) {
-            this.setToken(null);
-            window.location.href = '/';
-        }
-
-        if (!response.ok) {
-            let errorData;
-            try {
-                errorData = await response.json();
-            } catch (e) {
-                errorData = { message: 'Unknown error' };
+            if (this.token && !options.skipAuth) {
+                headers['Authorization'] = `Bearer ${this.token}`;
             }
-            const errorMessage = errorData.detail || errorData.message || 'Request failed';
-            document.dispatchEvent(new CustomEvent('show-toast', {
-                detail: { message: errorMessage, type: 'error' }
-            }));
-            throw new Error(errorMessage);
-        }
 
-        if (response.status === 204) {
-            return null;
-        }
+            const config = {
+                ...options,
+                headers,
+            };
 
-        return response.json();
+            if (config.body) {
+                if (config.body instanceof FormData) {
+                    let hasFile = false;
+                    for (let pair of config.body.entries()) {
+                        if (pair[1] instanceof File) {
+                            hasFile = true;
+                            break;
+                        }
+                    }
+
+                    if (!hasFile) {
+                        this.logger?.error('FormData without File objects not allowed - JSON only communication enforced');
+                        throw new Error('FormData is only allowed for file uploads');
+                    }
+
+                    this.logger?.debug('File upload detected, allowing FormData');
+                } else if (typeof config.body === 'object') {
+                    headers['Content-Type'] = 'application/json';
+                    config.body = JSON.stringify(config.body);
+                    this.logger?.debug('Request body serialized to JSON');
+                }
+            }
+
+            const response = await fetch(url, config);
+            const duration = performance.now() - startTime;
+
+            if (this.perfMonitor) {
+                this.perfMonitor._recordMetric('api-request', duration);
+                this.perfMonitor._recordMetric(`api-${method}`, duration);
+            }
+
+            if (response.status === 401) {
+                this.logger?.warn('Unauthorized request, clearing token');
+                this.setToken(null);
+                window.location.href = '/';
+            }
+
+            if (!response.ok) {
+                let errorData;
+                try {
+                    errorData = await response.json();
+                } catch (e) {
+                    errorData = { message: 'Unknown error' };
+                }
+                const errorMessage = errorData.detail || errorData.message || 'Request failed';
+
+                this.logger?.error(`API ${method} ${endpoint} failed: ${errorMessage}`, {
+                    status: response.status,
+                    duration: `${duration.toFixed(2)}ms`
+                });
+
+                document.dispatchEvent(new CustomEvent('show-toast', {
+                    detail: { message: errorMessage, type: 'error' }
+                }));
+                throw new Error(errorMessage);
+            }
+
+            this.logger?.debug(`API ${method} ${endpoint} success`, {
+                status: response.status,
+                duration: `${duration.toFixed(2)}ms`
+            });
+
+            if (response.status === 204) {
+                return null;
+            }
+
+            const contentType = response.headers.get('content-type');
+            if (!contentType || !contentType.includes('application/json')) {
+                this.logger?.error(`Invalid response content-type: ${contentType}. Expected application/json`);
+                throw new Error('Server returned non-JSON response');
+            }
+
+            return response.json();
+        } catch (error) {
+            this.logger?.error(`API ${method} ${endpoint} exception`, error);
+            throw error;
+        } finally {
+            this.activeRequests--;
+            if (this.activeRequests === 0) {
+                this.appState?.setState({ isLoading: false });
+            }
+        }
     }
 
     async register(username, email, password) {
+        this.logger?.info('Attempting registration', { username, email });
+
         const data = await this.request('auth/register', {
             method: 'POST',
             body: { username, email, password },
             skipAuth: true
         });
+
+        if (!data || !data.access_token) {
+            this.logger?.error('Invalid registration response: missing access_token', data);
+            throw new Error('Invalid registration response');
+        }
+
+        this.logger?.info('Registration successful', { username });
         this.setToken(data.access_token);
         return data;
     }
 
     async login(username, password) {
-        const formData = new FormData();
-        formData.append('username', username);
-        formData.append('password', password);
+        this.logger?.info('Attempting login', { username });
 
         const data = await this.request('auth/token', {
             method: 'POST',
-            body: formData,
+            body: { username, password },
             skipAuth: true
         });
+
+        if (!data || !data.access_token) {
+            this.logger?.error('Invalid login response: missing access_token', data);
+            throw new Error('Invalid authentication response');
+        }
+
+        this.logger?.info('Login successful', { username });
         this.setToken(data.access_token);
         return data;
     }
@@ -328,4 +403,28 @@ class APIClient {
     }
 }
 
-export const api = new APIClient();
+export { APIClient };
+
+let _sharedInstance = null;
+
+export function setSharedAPIInstance(instance) {
+    _sharedInstance = instance;
+}
+
+export const api = new Proxy({}, {
+    get(target, prop) {
+        if (!_sharedInstance) {
+            console.warn('API instance accessed before initialization. This may cause issues with logging and state management.');
+            _sharedInstance = new APIClient();
+        }
+
+        const instance = _sharedInstance;
+        const value = instance[prop];
+
+        if (typeof value === 'function') {
+            return value.bind(instance);
+        }
+
+        return value;
+    }
+});
diff --git a/static/js/app.js b/static/js/app.js
new file mode 100644
index 0000000..66aa001
--- /dev/null
+++ b/static/js/app.js
@@ -0,0 +1,111 @@
+import Logger from './logger.js';
+import AppState from './state.js';
+import PerformanceMonitor from './perf-monitor.js';
+import LazyLoader from './lazy-loader.js';
+import { APIClient, setSharedAPIInstance } from './api.js';
+
+class Application {
+    constructor() {
+        try {
+            this.logger = new Logger({
+                level: 'debug',
+                maxLogs: 200,
+                enableRemote: false
+            });
+
+            this.appState = new AppState({
+                currentView: 'files',
+                currentPage: 'files',
+                user: null,
+                isLoading: false,
+                notifications: []
+            });
+
+            this.perfMonitor = new PerformanceMonitor(this.logger);
+
+            this.api = new APIClient('/', this.logger, this.perfMonitor, this.appState);
+
+            setSharedAPIInstance(this.api);
+
+            this.lazyLoader = new LazyLoader({
+                threshold: 0.1,
+                rootMargin: '50px',
+                logger: this.logger
+            });
+
+            this._setupStateSubscriptions();
+            this._makeGloballyAccessible();
+
+            this.initialized = true;
+
+            this.logger.info('Application initialized successfully', {
+                version: '1.0.0',
+                timestamp: new Date().toISOString()
+            });
+        } catch (error) {
+            console.error('CRITICAL: Application initialization failed', error);
+            this.initialized = false;
+            throw error;
+        }
+    }
+
+    _setupStateSubscriptions() {
+        this.appState.subscribe((newState, prevState, action) => {
+            this.logger.debug('State changed', {
+                from: prevState,
+                to: newState,
+                action
+            });
+        });
+    }
+
+    _makeGloballyAccessible() {
+        if (typeof window !== 'undefined') {
+            window.app = this;
+        }
+    }
+
+    isReady() {
+        return this.initialized === true;
+    }
+
+    getLogger() {
+        if (!this.initialized) {
+            console.warn('Application not fully initialized');
+        }
+        return this.logger;
+    }
+
+    getState() {
+        if (!this.initialized) {
+            console.warn('Application not fully initialized');
+        }
+        return this.appState;
+    }
+
+    getAPI() {
+        if (!this.initialized) {
+            console.warn('Application not fully initialized');
+        }
+        return this.api;
+    }
+
+    getPerfMonitor() {
+        if (!this.initialized) {
+            console.warn('Application not fully initialized');
+        }
+        return this.perfMonitor;
+    }
+
+    getLazyLoader() {
+        if (!this.initialized) {
+            console.warn('Application not fully initialized');
+        }
+        return this.lazyLoader;
+    }
+}
+
+const app = new Application();
+
+export { Application, app };
+export default app;
diff --git a/static/js/components/admin-billing.js b/static/js/components/admin-billing.js
index 06d93f6..36ca47d 100644
--- a/static/js/components/admin-billing.js
+++ b/static/js/components/admin-billing.js
@@ -4,6 +4,8 @@ class AdminBilling extends HTMLElement {
         this.pricingConfig = [];
         this.stats = null;
         this.boundHandleClick = this.handleClick.bind(this);
+        this.loading = true;
+        this.error = null;
     }
 
     async connectedCallback() {
@@ -18,6 +20,8 @@ class AdminBilling extends HTMLElement {
     }
 
     async loadData() {
+        this.loading = true;
+        this.error = null;
         try {
             const [pricing, stats] = await Promise.all([
                 this.fetchPricing(),
@@ -26,8 +30,11 @@ class AdminBilling extends HTMLElement {
 
             this.pricingConfig = pricing;
             this.stats = stats;
+            this.loading = false;
         } catch (error) {
             console.error('Failed to load admin billing data:', error);
+            this.error = error.message || 'Failed to load admin billing data';
+            this.loading = false;
         }
     }
 
@@ -53,6 +60,16 @@ class AdminBilling extends HTMLElement {
     }
 
     render() {
+        if (this.loading) {
+            this.innerHTML = '<div class="admin-billing"><div class="loading">Loading admin billing data...</div></div>';
+            return;
+        }
+
+        if (this.error) {
+            this.innerHTML = `<div class="admin-billing"><div class="error-message">Error: ${this.error}</div></div>`;
+            return;
+        }
+
         this.innerHTML = `
             <div class="admin-billing">
                 <h2>Billing Administration</h2>
diff --git a/static/js/components/base-component.js b/static/js/components/base-component.js
new file mode 100644
index 0000000..6ac437d
--- /dev/null
+++ b/static/js/components/base-component.js
@@ -0,0 +1,78 @@
+export default class BaseComponent extends HTMLElement {
+    constructor() {
+        super();
+        this.attachShadow({ mode: 'open' });
+        this._state = {};
+        this._unsubscribers = [];
+    }
+
+    connectedCallback() {
+        this.render();
+        this._setupListeners();
+        this._subscribe();
+    }
+
+    disconnectedCallback() {
+        this._unsubscribers.forEach(unsubscribe => unsubscribe?.());
+        this._cleanup();
+    }
+
+    attributeChangedCallback(name, oldValue, newValue) {
+        if (oldValue !== newValue) {
+            this.render();
+        }
+    }
+
+    render() {
+        if (!this.shadowRoot) return;
+
+        const style = this._getStyles();
+        const template = this._getTemplate();
+
+        this.shadowRoot.innerHTML = `${style}${template}`;
+    }
+
+    _getStyles() {
+        return '<style>:host { display: block; }</style>';
+    }
+
+    _getTemplate() {
+        return '';
+    }
+
+    _setupListeners() {
+    }
+
+    _subscribe() {
+    }
+
+    _cleanup() {
+    }
+
+    emit(eventName, detail = {}) {
+        this.dispatchEvent(
+            new CustomEvent(eventName, {
+                detail,
+                bubbles: true,
+                composed: true
+            })
+        );
+    }
+
+    setState(updates) {
+        this._state = { ...this._state, ...updates };
+        this.render();
+    }
+
+    getState() {
+        return { ...this._state };
+    }
+
+    querySelector(selector) {
+        return this.shadowRoot?.querySelector(selector);
+    }
+
+    querySelectorAll(selector) {
+        return this.shadowRoot?.querySelectorAll(selector) || [];
+    }
+}
diff --git a/static/js/components/billing-dashboard.js b/static/js/components/billing-dashboard.js
index bfd1702..7c6e23e 100644
--- a/static/js/components/billing-dashboard.js
+++ b/static/js/components/billing-dashboard.js
@@ -6,13 +6,18 @@ class BillingDashboard extends HTMLElement {
         this.pricing = null;
         this.invoices = [];
         this.boundHandleClick = this.handleClick.bind(this);
+        this.loading = true;
+        this.error = null;
+        this.stripe = null;
     }
 
     async connectedCallback() {
         this.addEventListener('click', this.boundHandleClick);
+        this.render();
         await this.loadData();
         this.render();
         this.attachEventListeners();
+        await this.initStripe();
     }
 
     disconnectedCallback() {
@@ -20,6 +25,8 @@ class BillingDashboard extends HTMLElement {
     }
 
     async loadData() {
+        this.loading = true;
+        this.error = null;
         try {
             const [usage, subscription, pricing, invoices] = await Promise.all([
                 this.fetchCurrentUsage(),
@@ -32,8 +39,21 @@ class BillingDashboard extends HTMLElement {
             this.subscription = subscription;
             this.pricing = pricing;
             this.invoices = invoices;
+            this.loading = false;
         } catch (error) {
             console.error('Failed to load billing data:', error);
+            this.error = error.message || 'Failed to load billing data';
+            this.loading = false;
+        }
+    }
+
+    async initStripe() {
+        if (window.Stripe) {
+            const response = await fetch('/api/billing/stripe-key');
+            if (response.ok) {
+                const data = await response.json();
+                this.stripe = window.Stripe(data.publishable_key);
+            }
         }
     }
 
@@ -109,6 +129,16 @@ class BillingDashboard extends HTMLElement {
     }
 
     render() {
+        if (this.loading) {
+            this.innerHTML = '<div class="billing-dashboard"><div class="loading">Loading billing data...</div></div>';
+            return;
+        }
+
+        if (this.error) {
+            this.innerHTML = `<div class="billing-dashboard"><div class="error-message">Error: ${this.error}</div></div>`;
+            return;
+        }
+
         const estimatedCost = this.calculateEstimatedCost();
         const storageUsed = this.currentUsage?.storage_gb || 0;
         const freeStorage = parseFloat(this.pricing?.free_tier_storage_gb?.value || 15);
@@ -253,7 +283,74 @@ class BillingDashboard extends HTMLElement {
     }
 
     async showPaymentMethodModal() {
-        alert('Payment method modal will be implemented with Stripe Elements');
+        if (!this.stripe) {
+            alert('Payment processing not available');
+            return;
+        }
+
+        try {
+            const response = await fetch('/api/billing/payment-methods/setup-intent', {
+                method: 'POST',
+                headers: {'Authorization': `Bearer ${localStorage.getItem('token')}`}
+            });
+
+            if (!response.ok) {
+                const error = await response.json();
+                alert(`Failed to initialize payment: ${error.detail}`);
+                return;
+            }
+
+            const { client_secret } = await response.json();
+
+            const modal = document.createElement('div');
+            modal.className = 'modal';
+            modal.innerHTML = `
+                <div class="modal-content">
+                    <h2>Add Payment Method</h2>
+                    <div id="payment-element"></div>
+                    <div class="modal-actions">
+                        <button class="btn-primary" id="submitPayment">Add Card</button>
+                        <button class="btn-secondary" id="cancelPayment">Cancel</button>
+                    </div>
+                </div>
+            `;
+            document.body.appendChild(modal);
+
+            const elements = this.stripe.elements({ clientSecret: client_secret });
+            const paymentElement = elements.create('payment');
+            paymentElement.mount('#payment-element');
+
+            modal.querySelector('#submitPayment').addEventListener('click', async () => {
+                const submitButton = modal.querySelector('#submitPayment');
+                submitButton.disabled = true;
+                submitButton.textContent = 'Processing...';
+
+                const { error } = await this.stripe.confirmSetup({
+                    elements,
+                    confirmParams: {
+                        return_url: window.location.href,
+                    },
+                    redirect: 'if_required'
+                });
+
+                if (error) {
+                    alert(`Payment failed: ${error.message}`);
+                    submitButton.disabled = false;
+                    submitButton.textContent = 'Add Card';
+                } else {
+                    alert('Payment method added successfully');
+                    modal.remove();
+                    await this.loadData();
+                    this.render();
+                }
+            });
+
+            modal.querySelector('#cancelPayment').addEventListener('click', () => {
+                modal.remove();
+            });
+        } catch (error) {
+            alert(`Error: ${error.message}`);
+        }
     }
 
     async showInvoiceDetail(invoiceId) {
diff --git a/static/js/components/code-editor-view.js b/static/js/components/code-editor-view.js
index 39014f4..9c318e9 100644
--- a/static/js/components/code-editor-view.js
+++ b/static/js/components/code-editor-view.js
@@ -1,4 +1,7 @@
-import { api } from '../api.js';
+import app from '../app.js';
+
+const api = app.getAPI();
+const logger = app.getLogger();
 
 class CodeEditorView extends HTMLElement {
     constructor() {
@@ -6,146 +9,205 @@ class CodeEditorView extends HTMLElement {
         this.editor = null;
         this.file = null;
         this.previousView = null;
-        this.boundHandleClick = this.handleClick.bind(this);
-        this.boundHandleEscape = this.handleEscape.bind(this);
+        this.isRendered = false;
     }
 
     connectedCallback() {
-        this.addEventListener('click', this.boundHandleClick);
-        document.addEventListener('keydown', this.boundHandleEscape);
+        logger.debug('CodeEditorView connected');
     }
 
     disconnectedCallback() {
-        this.removeEventListener('click', this.boundHandleClick);
-        document.removeEventListener('keydown', this.boundHandleEscape);
-        if (this.editor) {
-            this.editor.toTextArea();
-            this.editor = null;
-        }
-    }
-
-    handleEscape(e) {
-        if (e.key === 'Escape') {
-            this.goBack();
-        }
+        logger.debug('CodeEditorView disconnected');
+        this.destroyEditor();
     }
 
     async setFile(file, previousView = 'files') {
+        if (this.isRendered) {
+            logger.warn('Editor already rendered, skipping');
+            return;
+        }
+
         this.file = file;
         this.previousView = previousView;
-        await this.loadAndRender();
-    }
+        this.isRendered = true;
 
-    async loadAndRender() {
         try {
-            const blob = await api.downloadFile(this.file.id);
+            logger.debug('Loading file', { fileName: file.name });
+            const blob = await api.downloadFile(file.id);
             const content = await blob.text();
-            this.render(content);
-            this.initializeEditor(content);
+
+            this.createUI(content);
+            this.createEditor(content);
         } catch (error) {
-            console.error('Failed to load file:', error);
+            logger.error('Failed to load file', error);
             document.dispatchEvent(new CustomEvent('show-toast', {
                 detail: { message: 'Failed to load file: ' + error.message, type: 'error' }
             }));
-            this.render('');
             window.history.back();
         }
     }
 
-    getMimeType(filename) {
-        const extension = filename.split('.').pop().toLowerCase();
-        const mimeMap = {
-            'js': 'text/javascript',
-            'json': 'application/json',
-            'py': 'text/x-python',
-            'md': 'text/x-markdown',
-            'html': 'text/html',
-            'xml': 'application/xml',
-            'css': 'text/css',
-            'txt': 'text/plain',
-            'log': 'text/plain',
-            'sh': 'text/x-sh',
-            'yaml': 'text/x-yaml',
-            'yml': 'text/x-yaml'
-        };
-        return mimeMap[extension] || 'text/plain';
-    }
-
-    render(content) {
+    createUI(content) {
         this.innerHTML = `
-            <div class="code-editor-view">
-                <div class="code-editor-header">
-                    <div class="header-left">
-                        <button class="button" id="back-btn">Back</button>
-                        <h2 class="editor-filename">${this.file.name}</h2>
+            <div class="code-editor-overlay">
+                <div class="code-editor-container">
+                    <div class="code-editor-header">
+                        <div class="header-left">
+                            <button class="button" id="back-btn">Back</button>
+                            <h2 class="editor-filename">${this.escapeHtml(this.file.name)}</h2>
+                        </div>
+                        <div class="header-right">
+                            <button class="button button-primary" id="save-btn">Save & Close</button>
+                        </div>
                     </div>
-                    <div class="header-right">
-                        <button class="button button-primary" id="save-btn">Save</button>
+                    <div class="code-editor-body">
+                        <textarea id="editor-textarea"></textarea>
                     </div>
                 </div>
-                <div class="code-editor-body">
-                    <textarea id="code-editor-textarea">${content}</textarea>
-                </div>
             </div>
         `;
+
+        const backBtn = this.querySelector('#back-btn');
+        const saveBtn = this.querySelector('#save-btn');
+
+        backBtn.addEventListener('click', () => this.close());
+        saveBtn.addEventListener('click', () => this.save());
+
+        document.addEventListener('keydown', this.handleKeydown.bind(this));
     }
 
-    initializeEditor(content) {
-        const textarea = this.querySelector('#code-editor-textarea');
-        if (!textarea) return;
+    createEditor(content) {
+        const textarea = this.querySelector('#editor-textarea');
+        if (!textarea) {
+            logger.error('Textarea not found');
+            return;
+        }
+
+        textarea.value = content;
+
+        const mode = this.getMode(this.file.name);
+        logger.debug('Creating CodeMirror editor', { mode, fileSize: content.length });
 
         this.editor = CodeMirror.fromTextArea(textarea, {
-            value: content,
-            mode: this.getMimeType(this.file.name),
+            mode: mode,
             lineNumbers: true,
-            theme: 'default',
             lineWrapping: true,
             indentUnit: 4,
             indentWithTabs: false,
+            theme: 'default',
+            readOnly: false,
+            autofocus: true,
             extraKeys: {
-                'Ctrl-S': () => this.save(),
-                'Cmd-S': () => this.save()
+                'Ctrl-S': () => { this.save(); return false; },
+                'Cmd-S': () => { this.save(); return false; },
+                'Esc': () => { this.close(); return false; }
             }
         });
 
         this.editor.setSize('100%', '100%');
+
+        setTimeout(() => {
+            if (this.editor) {
+                this.editor.refresh();
+                this.editor.focus();
+                logger.debug('Editor ready and focused');
+            }
+        }, 100);
     }
 
-    handleClick(e) {
-        if (e.target.id === 'back-btn') {
-            this.goBack();
-        } else if (e.target.id === 'save-btn') {
-            this.save();
+    getMode(filename) {
+        const ext = filename.split('.').pop().toLowerCase();
+        const modes = {
+            'js': 'javascript',
+            'json': { name: 'javascript', json: true },
+            'py': 'python',
+            'md': 'markdown',
+            'html': 'htmlmixed',
+            'xml': 'xml',
+            'css': 'css',
+            'txt': 'text/plain',
+            'log': 'text/plain',
+            'sh': 'shell',
+            'yaml': 'yaml',
+            'yml': 'yaml'
+        };
+        return modes[ext] || 'text/plain';
+    }
+
+    escapeHtml(text) {
+        const div = document.createElement('div');
+        div.textContent = text;
+        return div.innerHTML;
+    }
+
+    handleKeydown(e) {
+        if (e.key === 'Escape' && !this.editor.getOption('readOnly')) {
+            this.close();
         }
     }
 
     async save() {
-        if (!this.editor) return;
+        if (!this.editor) {
+            logger.warn('No editor instance');
+            return;
+        }
+
+        const saveBtn = this.querySelector('#save-btn');
+        if (!saveBtn) return;
 
         try {
+            saveBtn.disabled = true;
+            saveBtn.textContent = 'Saving...';
+
             const content = this.editor.getValue();
+            logger.debug('Saving file', { fileName: this.file.name, size: content.length });
+
             await api.updateFile(this.file.id, content);
+
+            logger.info('File saved successfully', { fileName: this.file.name });
+
             document.dispatchEvent(new CustomEvent('show-toast', {
                 detail: { message: 'File saved successfully!', type: 'success' }
             }));
+
+            setTimeout(() => {
+                this.close();
+            }, 500);
+
         } catch (error) {
+            logger.error('Failed to save file', error);
             document.dispatchEvent(new CustomEvent('show-toast', {
-                detail: { message: 'Failed to save file: ' + error.message, type: 'error' }
+                detail: { message: 'Failed to save: ' + error.message, type: 'error' }
             }));
+
+            if (saveBtn) {
+                saveBtn.disabled = false;
+                saveBtn.textContent = 'Save & Close';
+            }
         }
     }
 
-    goBack() {
+    close() {
+        logger.debug('Closing editor');
         window.history.back();
     }
 
     hide() {
-        document.removeEventListener('keydown', this.boundHandleEscape);
+        logger.debug('Hiding editor');
+        this.destroyEditor();
+        this.remove();
+    }
+
+    destroyEditor() {
         if (this.editor) {
-            this.editor.toTextArea();
+            logger.debug('Destroying CodeMirror instance');
+            try {
+                this.editor.toTextArea();
+            } catch (e) {
+                logger.warn('Error destroying editor', e);
+            }
             this.editor = null;
         }
-        this.remove();
     }
 }
 
diff --git a/static/js/components/error-boundary.js b/static/js/components/error-boundary.js
new file mode 100644
index 0000000..30f944f
--- /dev/null
+++ b/static/js/components/error-boundary.js
@@ -0,0 +1,101 @@
+import BaseComponent from './base-component.js';
+
+export default class ErrorBoundary extends BaseComponent {
+    constructor() {
+        super();
+        this.error = null;
+        this.errorInfo = null;
+    }
+
+    _getStyles() {
+        return `<style>
+            :host {
+                display: block;
+            }
+
+            .error-container {
+                padding: 2rem;
+                background: #ffebee;
+                border: 1px solid #f44336;
+                border-radius: 8px;
+                color: #c62828;
+            }
+
+            h2 {
+                margin: 0 0 1rem 0;
+                font-size: 1.5rem;
+            }
+
+            p {
+                margin: 0 0 0.5rem 0;
+                line-height: 1.6;
+            }
+
+            .error-details {
+                background: rgba(0, 0, 0, 0.1);
+                padding: 1rem;
+                border-radius: 4px;
+                font-family: monospace;
+                font-size: 0.85rem;
+                overflow-x: auto;
+                max-height: 200px;
+                overflow-y: auto;
+                margin-top: 1rem;
+            }
+
+            .error-details pre {
+                margin: 0;
+                white-space: pre-wrap;
+                word-wrap: break-word;
+            }
+
+            button {
+                margin-top: 1rem;
+                padding: 0.75rem 1.5rem;
+                background: #f44336;
+                color: white;
+                border: none;
+                border-radius: 4px;
+                cursor: pointer;
+                font-weight: 600;
+            }
+
+            button:hover {
+                background: #d32f2f;
+            }
+        </style>`;
+    }
+
+    _getTemplate() {
+        if (!this.error) {
+            return '<slot></slot>';
+        }
+
+        return `
+            <div class="error-container" role="alert">
+                <h2>Something went wrong</h2>
+                <p>${this.error.message || 'An unexpected error occurred'}</p>
+                <p>Please refresh the page or contact support if the problem persists.</p>
+                <div class="error-details">
+                    <pre>${this.error.stack || 'No stack trace available'}</pre>
+                </div>
+                <button type="button" onclick="location.reload()">Reload Page</button>
+            </div>
+        `;
+    }
+
+    catch(error, errorInfo) {
+        this.error = error;
+        this.errorInfo = errorInfo;
+        this.render();
+        console.error('Error caught by boundary:', error, errorInfo);
+    }
+
+    reset() {
+        this.error = null;
+        this.errorInfo = null;
+        this.render();
+    }
+}
+
+customElements.define('error-boundary', ErrorBoundary);
diff --git a/static/js/components/file-preview.js b/static/js/components/file-preview.js
index 144be90..4461902 100644
--- a/static/js/components/file-preview.js
+++ b/static/js/components/file-preview.js
@@ -41,14 +41,6 @@ class FilePreview extends HTMLElement {
         this.style.display = 'block';
         document.addEventListener('keydown', this.handleEscape);
         this.renderPreview();
-
-        if (pushState) {
-            window.history.pushState(
-                { view: 'file-preview', file: file },
-                '',
-                `#preview/${file.id}`
-            );
-        }
     }
 
     close() {
diff --git a/static/js/components/login-view.js b/static/js/components/login-view.js
index d54abbc..d1bf091 100644
--- a/static/js/components/login-view.js
+++ b/static/js/components/login-view.js
@@ -1,4 +1,7 @@
-import { api } from '../api.js';
+import app from '../app.js';
+
+const api = app.getAPI();
+const logger = app.getLogger();
 
 export class LoginView extends HTMLElement {
     constructor() {
@@ -74,9 +77,12 @@ export class LoginView extends HTMLElement {
         const errorDiv = this.querySelector('#login-error');
 
         try {
+            logger.info('Login attempt started', { username });
             await api.login(username, password);
+            logger.info('Login successful, dispatching auth-success event');
             this.dispatchEvent(new CustomEvent('auth-success'));
         } catch (error) {
+            logger.error('Login failed', { username, error: error.message });
             errorDiv.textContent = error.message;
         }
     }
@@ -91,9 +97,12 @@ export class LoginView extends HTMLElement {
         const errorDiv = this.querySelector('#register-error');
 
         try {
+            logger.info('Registration attempt started', { username, email });
             await api.register(username, email, password);
+            logger.info('Registration successful, dispatching auth-success event');
             this.dispatchEvent(new CustomEvent('auth-success'));
         } catch (error) {
+            logger.error('Registration failed', { username, email, error: error.message });
             errorDiv.textContent = error.message;
         }
     }
diff --git a/static/js/components/rbox-app.js b/static/js/components/rbox-app.js
index fda6cbd..ff1cf08 100644
--- a/static/js/components/rbox-app.js
+++ b/static/js/components/rbox-app.js
@@ -1,4 +1,4 @@
-import { api } from '../api.js';
+import app from '../app.js';
 import './login-view.js';
 import './file-list.js';
 import './file-upload-view.js';
@@ -16,22 +16,51 @@ import './admin-billing.js';
 import './code-editor-view.js';
 import { shortcuts } from '../shortcuts.js';
 
+const api = app.getAPI();
+const logger = app.getLogger();
+const appState = app.getState();
+
 export class RBoxApp extends HTMLElement {
     constructor() {
         super();
         this.currentView = 'files';
         this.user = null;
         this.navigationStack = [];
+        this.boundHandlePopState = this.handlePopState.bind(this);
+        this.popstateAttached = false;
     }
 
     async connectedCallback() {
-        await this.init();
-        this.addEventListener('show-toast', this.handleShowToast);
-        window.addEventListener('popstate', this.handlePopState.bind(this));
+        try {
+            await this.init();
+            this.addEventListener('show-toast', this.handleShowToast);
+
+            if (!this.popstateAttached) {
+                window.addEventListener('popstate', this.boundHandlePopState);
+                this.popstateAttached = true;
+                logger.debug('Popstate listener attached');
+            }
+        } catch (error) {
+            logger.error('Failed to initialize RBoxApp', error);
+            this.innerHTML = `
+                <div style="padding: 2rem; text-align: center; font-family: sans-serif;">
+                    <h1 style="color: #d32f2f;">Failed to Load Application</h1>
+                    <p>${error.message}</p>
+                    <button onclick="location.reload()" style="padding: 0.75rem 1.5rem; background: #2196F3; color: white; border: none; border-radius: 4px; cursor: pointer; font-size: 1rem;">
+                        Reload Page
+                    </button>
+                </div>
+            `;
+        }
     }
 
     disconnectedCallback() {
         this.removeEventListener('show-toast', this.handleShowToast);
+        if (this.popstateAttached) {
+            window.removeEventListener('popstate', this.boundHandlePopState);
+            this.popstateAttached = false;
+            logger.debug('Popstate listener removed');
+        }
     }
 
     handleShowToast = (event) => {
@@ -46,15 +75,21 @@ export class RBoxApp extends HTMLElement {
     }
 
     async init() {
-        if (!api.getToken()) {
-            this.showLogin();
-        } else {
-            try {
-                this.user = await api.getCurrentUser();
-                this.render();
-            } catch (error) {
+        try {
+            if (!api.getToken()) {
+                logger.info('No token found, showing login');
                 this.showLogin();
+            } else {
+                logger.info('Initializing application with stored token');
+                this.user = await api.getCurrentUser();
+                appState.setState({ user: this.user });
+                logger.info('User loaded successfully', { username: this.user.username });
+                this.render();
             }
+        } catch (error) {
+            logger.error('Failed to initialize application', error);
+            api.setToken(null);
+            this.showLogin();
         }
     }
 
@@ -383,47 +418,63 @@ export class RBoxApp extends HTMLElement {
     }
 
     handlePopState(e) {
+        logger.debug('Popstate event', { state: e.state, url: window.location.href });
+
         this.closeAllOverlays();
 
         if (e.state && e.state.view) {
-            if (e.state.view === 'code-editor' && e.state.file) {
+            const view = e.state.view;
+
+            if (view === 'code-editor' && e.state.file) {
+                logger.debug('Restoring code editor view');
                 this.showCodeEditor(e.state.file, false);
-            } else if (e.state.view === 'file-preview' && e.state.file) {
+            } else if (view === 'file-preview' && e.state.file) {
+                logger.debug('Restoring file preview view');
                 this.showFilePreview(e.state.file, false);
-            } else if (e.state.view === 'upload') {
+            } else if (view === 'upload') {
+                logger.debug('Restoring upload view');
                 const folderId = e.state.folderId !== undefined ? e.state.folderId : null;
                 this.showUpload(folderId, false);
             } else {
-                this.switchView(e.state.view, false);
+                logger.debug('Switching to view', { view });
+                this.switchView(view, false);
             }
         } else {
+            logger.debug('No state, defaulting to files view');
             this.switchView('files', false);
         }
     }
 
     closeAllOverlays() {
+        logger.debug('Closing all overlays');
+
         const existingEditor = this.querySelector('code-editor-view');
         if (existingEditor) {
+            logger.debug('Hiding code editor');
             existingEditor.hide();
         }
 
         const existingPreview = this.querySelector('file-preview');
         if (existingPreview) {
+            logger.debug('Hiding file preview');
             existingPreview.hide();
         }
 
         const existingUpload = this.querySelector('file-upload-view');
         if (existingUpload) {
+            logger.debug('Hiding file upload');
             existingUpload.hide();
         }
 
         const shareModal = this.querySelector('share-modal');
         if (shareModal && shareModal.style.display !== 'none') {
+            logger.debug('Hiding share modal');
             shareModal.style.display = 'none';
         }
     }
 
     showCodeEditor(file, pushState = true) {
+        logger.debug('Showing code editor', { file: file.name, pushState });
         this.closeAllOverlays();
 
         const mainElement = this.querySelector('.app-main');
@@ -432,15 +483,29 @@ export class RBoxApp extends HTMLElement {
         editorView.setFile(file, this.currentView);
 
         if (pushState) {
-            window.history.pushState(
-                { view: 'code-editor', file: file },
-                '',
-                `#editor/${file.id}`
-            );
+            const currentState = window.history.state || {};
+            const currentView = currentState.view || this.currentView;
+
+            if (currentView !== 'code-editor') {
+                window.history.pushState(
+                    { view: 'code-editor', file: file, previousView: currentView },
+                    '',
+                    `#editor/${file.id}`
+                );
+                logger.debug('Pushed code editor state', { previousView: currentView });
+            } else {
+                logger.debug('Already in code editor view, replacing state');
+                window.history.replaceState(
+                    { view: 'code-editor', file: file, previousView: currentView },
+                    '',
+                    `#editor/${file.id}`
+                );
+            }
         }
     }
 
     showFilePreview(file, pushState = true) {
+        logger.debug('Showing file preview', { file: file.name, pushState });
         this.closeAllOverlays();
 
         const mainElement = this.querySelector('.app-main');
@@ -449,15 +514,29 @@ export class RBoxApp extends HTMLElement {
         preview.show(file, false);
 
         if (pushState) {
-            window.history.pushState(
-                { view: 'file-preview', file: file },
-                '',
-                `#preview/${file.id}`
-            );
+            const currentState = window.history.state || {};
+            const currentView = currentState.view || this.currentView;
+
+            if (currentView !== 'file-preview') {
+                window.history.pushState(
+                    { view: 'file-preview', file: file, previousView: currentView },
+                    '',
+                    `#preview/${file.id}`
+                );
+                logger.debug('Pushed file preview state', { previousView: currentView });
+            } else {
+                logger.debug('Already in file preview view, replacing state');
+                window.history.replaceState(
+                    { view: 'file-preview', file: file, previousView: currentView },
+                    '',
+                    `#preview/${file.id}`
+                );
+            }
         }
     }
 
     showUpload(folderId = null, pushState = true) {
+        logger.debug('Showing upload view', { folderId, pushState });
         this.closeAllOverlays();
 
         const mainElement = this.querySelector('.app-main');
@@ -466,11 +545,24 @@ export class RBoxApp extends HTMLElement {
         uploadView.setFolder(folderId);
 
         if (pushState) {
-            window.history.pushState(
-                { view: 'upload', folderId: folderId },
-                '',
-                '#upload'
-            );
+            const currentState = window.history.state || {};
+            const currentView = currentState.view || this.currentView;
+
+            if (currentView !== 'upload') {
+                window.history.pushState(
+                    { view: 'upload', folderId: folderId, previousView: currentView },
+                    '',
+                    '#upload'
+                );
+                logger.debug('Pushed upload state', { previousView: currentView });
+            } else {
+                logger.debug('Already in upload view, replacing state');
+                window.history.replaceState(
+                    { view: 'upload', folderId: folderId, previousView: currentView },
+                    '',
+                    '#upload'
+                );
+            }
         }
     }
 
diff --git a/static/js/fetch-interceptor.js b/static/js/fetch-interceptor.js
new file mode 100644
index 0000000..663b9c8
--- /dev/null
+++ b/static/js/fetch-interceptor.js
@@ -0,0 +1,47 @@
+export default class FetchInterceptor {
+    constructor(logger = null, appState = null, perfMonitor = null) {
+        this.logger = logger;
+        this.appState = appState;
+        this.perfMonitor = perfMonitor;
+        this.activeRequests = 0;
+    }
+
+    async request(url, options = {}) {
+        this.activeRequests++;
+        this.appState?.setState({ isLoading: true });
+
+        const startTime = performance.now();
+
+        try {
+            this.logger?.debug(`Fetch START: ${options.method || 'GET'} ${url}`);
+
+            const response = await fetch(url, {
+                ...options,
+                headers: {
+                    'Content-Type': 'application/json',
+                    ...options.headers
+                }
+            });
+
+            const duration = performance.now() - startTime;
+            this.perfMonitor?.['_recordMetric']?.('fetch', duration);
+
+            if (!response.ok) {
+                throw new Error(`HTTP ${response.status}: ${response.statusText}`);
+            }
+
+            const data = await response.json();
+            this.logger?.debug(`Fetch SUCCESS: ${url}`, { status: response.status, duration: `${duration.toFixed(2)}ms` });
+
+            return data;
+        } catch (error) {
+            this.logger?.error(`Fetch FAILED: ${url}`, { error: error.message });
+            throw error;
+        } finally {
+            this.activeRequests--;
+            if (this.activeRequests === 0) {
+                this.appState?.setState({ isLoading: false });
+            }
+        }
+    }
+}
diff --git a/static/js/focus-manager.js b/static/js/focus-manager.js
new file mode 100644
index 0000000..79b5028
--- /dev/null
+++ b/static/js/focus-manager.js
@@ -0,0 +1,83 @@
+export default class FocusManager {
+    static trapFocus(element, logger = null) {
+        const focusableSelectors = [
+            'button',
+            '[href]',
+            'input',
+            'select',
+            'textarea',
+            '[tabindex]:not([tabindex="-1"])'
+        ].join(', ');
+
+        const focusableElements = element.querySelectorAll(focusableSelectors);
+
+        if (focusableElements.length === 0) {
+            logger?.warn('No focusable elements found for trap');
+            return;
+        }
+
+        const firstElement = focusableElements[0];
+        const lastElement = focusableElements[focusableElements.length - 1];
+
+        const handleKeydown = (e) => {
+            if (e.key !== 'Tab') return;
+
+            if (e.shiftKey) {
+                if (document.activeElement === firstElement) {
+                    lastElement.focus();
+                    e.preventDefault();
+                }
+            } else {
+                if (document.activeElement === lastElement) {
+                    firstElement.focus();
+                    e.preventDefault();
+                }
+            }
+        };
+
+        element.addEventListener('keydown', handleKeydown);
+
+        return () => element.removeEventListener('keydown', handleKeydown);
+    }
+
+    static moveFocusToElement(element, options = {}) {
+        const { smooth = true, center = true } = options;
+
+        element.focus({ preventScroll: !smooth });
+
+        if (smooth) {
+            element.scrollIntoView({
+                behavior: 'smooth',
+                block: center ? 'center' : 'nearest'
+            });
+        }
+    }
+
+    static getFirstFocusableElement(container) {
+        const focusableSelectors = [
+            'button',
+            '[href]',
+            'input',
+            'select',
+            'textarea',
+            '[tabindex]:not([tabindex="-1"])'
+        ].join(', ');
+
+        return container.querySelector(focusableSelectors);
+    }
+
+    static restoreFocus(element) {
+        const prevElement = element.dataset.previousFocus;
+        if (prevElement) {
+            const el = document.querySelector(prevElement);
+            if (el) el.focus();
+        }
+    }
+
+    static saveFocus(element) {
+        const current = document.activeElement;
+        if (current) {
+            element.dataset.previousFocus = current.getAttribute('data-focus-id') || current.id;
+        }
+    }
+}
diff --git a/static/js/form-validator.js b/static/js/form-validator.js
new file mode 100644
index 0000000..2e434c6
--- /dev/null
+++ b/static/js/form-validator.js
@@ -0,0 +1,61 @@
+export default class FormValidator {
+    static rules = {
+        required: (value) => {
+            if (!value || (typeof value === 'string' && value.trim() === '')) {
+                return 'This field is required';
+            }
+            return null;
+        },
+        email: (value) => {
+            const regex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
+            return regex.test(value) ? null : 'Invalid email address';
+        },
+        minLength: (min) => (value) => {
+            return (value?.length || 0) >= min ? null : `Minimum ${min} characters required`;
+        },
+        maxLength: (max) => (value) => {
+            return (value?.length || 0) <= max ? null : `Maximum ${max} characters allowed`;
+        },
+        pattern: (regex, message = 'Invalid format') => (value) => {
+            return regex.test(value) ? null : message;
+        },
+        custom: (fn) => (value) => {
+            try {
+                const error = fn(value);
+                return error || null;
+            } catch (err) {
+                return 'Validation error';
+            }
+        }
+    };
+
+    static validate(formData, schema) {
+        const errors = {};
+
+        for (const [field, rules] of Object.entries(schema)) {
+            const value = formData[field];
+
+            for (const rule of rules) {
+                let error = null;
+
+                if (typeof rule === 'function') {
+                    error = rule(value);
+                }
+
+                if (error) {
+                    errors[field] = error;
+                    break;
+                }
+            }
+        }
+
+        return {
+            isValid: Object.keys(errors).length === 0,
+            errors
+        };
+    }
+
+    static createSchema() {
+        return {};
+    }
+}
diff --git a/static/js/lazy-loader.js b/static/js/lazy-loader.js
new file mode 100644
index 0000000..6420f42
--- /dev/null
+++ b/static/js/lazy-loader.js
@@ -0,0 +1,68 @@
+export default class LazyLoader {
+    constructor(options = {}) {
+        this.threshold = options.threshold || 0.1;
+        this.rootMargin = options.rootMargin || '50px';
+        this.observer = null;
+        this.logger = options.logger || null;
+        this._setup();
+    }
+
+    _setup() {
+        this.observer = new IntersectionObserver(
+            (entries) => {
+                entries.forEach((entry) => {
+                    if (entry.isIntersecting) {
+                        this._loadElement(entry.target);
+                        this.observer.unobserve(entry.target);
+                    }
+                });
+            },
+            {
+                threshold: this.threshold,
+                rootMargin: this.rootMargin
+            }
+        );
+    }
+
+    observe(element) {
+        if (!element) return;
+        this.observer.observe(element);
+    }
+
+    unobserve(element) {
+        if (!element) return;
+        this.observer.unobserve(element);
+    }
+
+    observeAll(selector) {
+        document.querySelectorAll(selector).forEach((el) => {
+            this.observe(el);
+        });
+    }
+
+    _loadElement(element) {
+        try {
+            if (element.dataset.src) {
+                element.src = element.dataset.src;
+                element.removeAttribute('data-src');
+                this.logger?.debug(`Lazy loaded image: ${element.src}`);
+            }
+
+            if (element.dataset.backgroundImage) {
+                element.style.backgroundImage = `url(${element.dataset.backgroundImage})`;
+                element.removeAttribute('data-background-image');
+                this.logger?.debug(`Lazy loaded background image`);
+            }
+
+            element.classList.add('loaded');
+        } catch (error) {
+            this.logger?.error('Failed to lazy load element', error);
+        }
+    }
+
+    destroy() {
+        if (this.observer) {
+            this.observer.disconnect();
+        }
+    }
+}
diff --git a/static/js/logger.js b/static/js/logger.js
new file mode 100644
index 0000000..266cb5a
--- /dev/null
+++ b/static/js/logger.js
@@ -0,0 +1,99 @@
+export default class Logger {
+    constructor(config = {}) {
+        this.levels = { debug: 0, info: 1, warn: 2, error: 3 };
+        this.currentLevel = config.level || 'info';
+        this.maxLogs = config.maxLogs || 100;
+        this.enableRemote = config.enableRemote || false;
+        this.remoteEndpoint = config.remoteEndpoint || '/api/logs';
+        this._setupGlobalHandlers();
+    }
+
+    log(level, message, data = null) {
+        const levelIndex = this.levels[level];
+        const currentIndex = this.levels[this.currentLevel];
+
+        if (levelIndex < currentIndex) return;
+
+        const timestamp = new Date().toISOString();
+        const entry = {
+            timestamp,
+            level,
+            message,
+            data,
+            url: window.location.href,
+            userAgent: navigator.userAgent
+        };
+
+        this._console(level, message, data);
+        this._persistLog(entry);
+
+        if (this.enableRemote && level === 'error') {
+            this._sendRemote(entry);
+        }
+    }
+
+    debug(message, data) { this.log('debug', message, data); }
+    info(message, data) { this.log('info', message, data); }
+    warn(message, data) { this.log('warn', message, data); }
+    error(message, data) { this.log('error', message, data); }
+
+    _console(level, message, data) {
+        const logFn = console[level] || console.log;
+        const timestamp = new Date().toISOString();
+        const prefix = `[${timestamp}] [${level.toUpperCase()}]`;
+        logFn(`${prefix} ${message}`, data || '');
+    }
+
+    _persistLog(entry) {
+        if (typeof localStorage === 'undefined') return;
+
+        try {
+            const logs = JSON.parse(localStorage.getItem('app_logs') || '[]');
+            logs.push(entry);
+
+            if (logs.length > this.maxLogs) {
+                logs.splice(0, logs.length - this.maxLogs);
+            }
+
+            localStorage.setItem('app_logs', JSON.stringify(logs));
+        } catch (err) {
+            console.error('Failed to persist log:', err);
+        }
+    }
+
+    _sendRemote(entry) {
+        fetch(this.remoteEndpoint, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify(entry)
+        }).catch(err => console.error('Remote logging failed:', err));
+    }
+
+    _setupGlobalHandlers() {
+        window.addEventListener('error', (event) => {
+            this.error(`JavaScript Error: ${event.message}`, {
+                file: event.filename,
+                line: event.lineno,
+                column: event.colno,
+                stack: event.error?.stack
+            });
+        });
+
+        window.addEventListener('unhandledrejection', (event) => {
+            this.error(`Unhandled Promise Rejection: ${event.reason}`, {
+                stack: event.reason?.stack
+            });
+        });
+    }
+
+    exportLogs() {
+        if (typeof localStorage === 'undefined') return [];
+        return JSON.parse(localStorage.getItem('app_logs') || '[]');
+    }
+
+    clearLogs() {
+        if (typeof localStorage !== 'undefined') {
+            localStorage.removeItem('app_logs');
+        }
+    }
+}
diff --git a/static/js/main.js b/static/js/main.js
index 703e106..ff5e48f 100644
--- a/static/js/main.js
+++ b/static/js/main.js
@@ -1,17 +1,61 @@
-import { RBoxApp } from './components/rbox-app.js';
+import { verifyStartup, showCompatibilityError } from './startup-check.js';
 
-// Define the custom element
-customElements.define('rbox-app', RBoxApp);
+const startupResults = verifyStartup();
 
-// Instantiate the main application class
-const app = new RBoxApp();
+if (startupResults.failed.length > 0) {
+    console.error('Startup checks failed:', startupResults.failed);
+    showCompatibilityError(startupResults);
+} else {
+    console.log('All startup checks passed');
 
-// Append the app to the body (if not already in index.html)
-// document.body.appendChild(app);
+    import('./app.js').then(({ default: app }) => {
+        return Promise.all([
+            import('./components/error-boundary.js'),
+            import('./components/rbox-app.js')
+        ]).then(([errorBoundary, rboxApp]) => {
+            if (!app.isReady()) {
+                console.error('CRITICAL: Application failed to initialize properly');
+                document.body.innerHTML = `
+                    <div style="padding: 2rem; text-align: center; font-family: sans-serif;">
+                        <h1 style="color: #d32f2f;">Application Failed to Initialize</h1>
+                        <p>Please refresh the page. If the problem persists, check the console for errors.</p>
+                        <button onclick="location.reload()" style="padding: 0.75rem 1.5rem; background: #2196F3; color: white; border: none; border-radius: 4px; cursor: pointer; font-size: 1rem;">
+                            Reload Page
+                        </button>
+                    </div>
+                `;
+                return;
+            }
 
-// Register service worker for PWA
-if ('serviceWorker' in navigator) {
-    window.addEventListener('load', () => {
-        navigator.serviceWorker.register('/static/service-worker.js');
+            customElements.define('rbox-app', rboxApp.RBoxApp);
+
+            if ('serviceWorker' in navigator) {
+                window.addEventListener('load', () => {
+                    navigator.serviceWorker.register('/static/service-worker.js').then(() => {
+                        app.getLogger().info('Service worker registered successfully');
+                    }).catch((error) => {
+                        app.getLogger().error('Service worker registration failed', error);
+                    });
+                });
+            }
+
+            app.getLogger().info('Main application loaded successfully');
+
+            window.addEventListener('load', () => {
+                app.getLazyLoader().observeAll('[data-src]');
+                app.getLogger().info('Application fully ready');
+            });
+        });
+    }).catch((error) => {
+        console.error('Failed to load application modules:', error);
+        document.body.innerHTML = `
+            <div style="padding: 2rem; text-align: center; font-family: sans-serif;">
+                <h1 style="color: #d32f2f;">Failed to Load Application</h1>
+                <p>${error.message}</p>
+                <button onclick="location.reload()" style="padding: 0.75rem 1.5rem; background: #2196F3; color: white; border: none; border-radius: 4px; cursor: pointer; font-size: 1rem;">
+                    Reload Page
+                </button>
+            </div>
+        `;
     });
 }
diff --git a/static/js/perf-monitor.js b/static/js/perf-monitor.js
new file mode 100644
index 0000000..342e47b
--- /dev/null
+++ b/static/js/perf-monitor.js
@@ -0,0 +1,71 @@
+export default class PerformanceMonitor {
+    constructor(logger = null) {
+        this.logger = logger;
+        this.metrics = new Map();
+    }
+
+    measureOperation(name, fn) {
+        const start = performance.now();
+        try {
+            const result = fn();
+            const duration = performance.now() - start;
+            this._recordMetric(name, duration);
+            return result;
+        } catch (error) {
+            this.logger?.error(`Operation ${name} failed`, error);
+            throw error;
+        }
+    }
+
+    async measureAsync(name, fn) {
+        const start = performance.now();
+        try {
+            const result = await fn();
+            const duration = performance.now() - start;
+            this._recordMetric(name, duration);
+            return result;
+        } catch (error) {
+            this.logger?.error(`Async operation ${name} failed`, error);
+            throw error;
+        }
+    }
+
+    _recordMetric(name, duration) {
+        if (!this.metrics.has(name)) {
+            this.metrics.set(name, []);
+        }
+
+        this.metrics.get(name).push(duration);
+        this.logger?.debug(`[PERF] ${name}: ${duration.toFixed(2)}ms`);
+    }
+
+    getMetrics(name) {
+        const values = this.metrics.get(name) || [];
+        return {
+            count: values.length,
+            min: Math.min(...values),
+            max: Math.max(...values),
+            avg: values.reduce((a, b) => a + b, 0) / values.length,
+            values
+        };
+    }
+
+    reportWebVitals() {
+        if ('web-vital' in window) {
+            const vitals = window['web-vital'];
+            this.logger?.info('Core Web Vitals', vitals);
+        }
+    }
+
+    getAllMetrics() {
+        const result = {};
+        for (const [name, values] of this.metrics.entries()) {
+            result[name] = this.getMetrics(name);
+        }
+        return result;
+    }
+
+    reset() {
+        this.metrics.clear();
+    }
+}
diff --git a/static/js/router.js b/static/js/router.js
new file mode 100644
index 0000000..a7f8b23
--- /dev/null
+++ b/static/js/router.js
@@ -0,0 +1,125 @@
+export default class Router {
+    constructor(options = {}) {
+        this.routes = new Map();
+        this.currentRoute = null;
+        this.basePath = options.basePath || '/';
+        this.transitionEnabled = true;
+        this.logger = options.logger || null;
+        this.appState = options.appState || null;
+        this._setupListeners();
+    }
+
+    register(path, handler, metadata = {}) {
+        this.routes.set(path, { handler, metadata });
+        return this;
+    }
+
+    async navigate(path, state = {}, skipTransition = false) {
+        try {
+            const route = this._matchRoute(path);
+
+            if (!route) {
+                this.logger?.warn(`No route found for: ${path}`);
+                return;
+            }
+
+            if (this.currentRoute?.path === path) return;
+
+            this.appState?.setState({ isLoading: true });
+
+            const performTransition = () => {
+                if (this.transitionEnabled && !skipTransition && document.startViewTransition) {
+                    document.startViewTransition(() => {
+                        this._executeRoute(path, route, state);
+                    }).finished.then(() => {
+                        this.appState?.setState({ isLoading: false });
+                    }).catch(err => {
+                        this.logger?.error('View transition failed', err);
+                        this.appState?.setState({ isLoading: false });
+                    });
+                } else {
+                    this._executeRoute(path, route, state);
+                    this.appState?.setState({ isLoading: false });
+                }
+            };
+
+            window.history.pushState(state, '', `${this.basePath}${path}`);
+            performTransition();
+        } catch (error) {
+            this.logger?.error(`Navigation error: ${error.message}`);
+            this.appState?.setState({ isLoading: false });
+        }
+    }
+
+    _executeRoute(path, route, state) {
+        const root = document.getElementById('app-root');
+        if (!root) return;
+
+        root.innerHTML = '';
+
+        this.currentRoute = { path, ...route };
+
+        try {
+            const result = route.handler(state);
+
+            if (result instanceof HTMLElement) {
+                root.appendChild(result);
+            } else if (typeof result === 'string') {
+                root.innerHTML = result;
+            }
+
+            this.appState?.setState({ currentPage: path });
+            window.dispatchEvent(new CustomEvent('route-changed', { detail: { path, state } }));
+        } catch (error) {
+            this.logger?.error(`Route handler failed for ${path}`, error);
+            root.innerHTML = '<h1>Error loading page</h1>';
+        }
+    }
+
+    _matchRoute(path) {
+        if (this.routes.has(path)) {
+            return this.routes.get(path);
+        }
+
+        for (const [routePath, route] of this.routes.entries()) {
+            const regex = this._pathToRegex(routePath);
+            if (regex.test(path)) {
+                return route;
+            }
+        }
+
+        return null;
+    }
+
+    _pathToRegex(path) {
+        const pattern = path
+            .replace(/\//g, '\\/')
+            .replace(/:(\w+)/g, '(?<$1>[^/]+)')
+            .replace(/\*/g, '.*');
+        return new RegExp(`^${pattern}$`);
+    }
+
+    _setupListeners() {
+        window.addEventListener('popstate', (event) => {
+            const path = window.location.pathname.replace(this.basePath, '') || '/';
+            this.navigate(path, event.state, true);
+        });
+
+        document.addEventListener('click', (event) => {
+            const link = event.target.closest('a[data-nav]');
+            if (link) {
+                event.preventDefault();
+                const path = link.getAttribute('href') || link.getAttribute('data-nav');
+                this.navigate(path);
+            }
+        });
+    }
+
+    back() {
+        window.history.back();
+    }
+
+    forward() {
+        window.history.forward();
+    }
+}
diff --git a/static/js/startup-check.js b/static/js/startup-check.js
new file mode 100644
index 0000000..182ec69
--- /dev/null
+++ b/static/js/startup-check.js
@@ -0,0 +1,89 @@
+export function verifyStartup() {
+    const checks = [];
+
+    checks.push({
+        name: 'LocalStorage Available',
+        test: () => {
+            try {
+                const test = '__storage_test__';
+                localStorage.setItem(test, test);
+                localStorage.removeItem(test);
+                return true;
+            } catch (e) {
+                return false;
+            }
+        }
+    });
+
+    checks.push({
+        name: 'Fetch API Available',
+        test: () => typeof fetch === 'function'
+    });
+
+    checks.push({
+        name: 'Promises Available',
+        test: () => typeof Promise === 'function'
+    });
+
+    checks.push({
+        name: 'Custom Elements Supported',
+        test: () => 'customElements' in window
+    });
+
+    checks.push({
+        name: 'ES6 Modules Supported',
+        test: () => {
+            try {
+                new Function('import("")');
+                return true;
+            } catch (e) {
+                return false;
+            }
+        }
+    });
+
+    const results = {
+        passed: [],
+        failed: []
+    };
+
+    for (const check of checks) {
+        try {
+            if (check.test()) {
+                results.passed.push(check.name);
+            } else {
+                results.failed.push(check.name);
+            }
+        } catch (error) {
+            results.failed.push(`${check.name} (Error: ${error.message})`);
+        }
+    }
+
+    return results;
+}
+
+export function showCompatibilityError(results) {
+    document.body.innerHTML = `
+        <div style="padding: 2rem; max-width: 600px; margin: 2rem auto; font-family: sans-serif; background: #fff; border-radius: 8px; box-shadow: 0 2px 8px rgba(0,0,0,0.1);">
+            <h1 style="color: #d32f2f; margin-bottom: 1rem;">Browser Not Supported</h1>
+            <p style="margin-bottom: 1rem;">Your browser does not support the required features for this application.</p>
+
+            <h3 style="color: #666; margin-top: 1.5rem;">Failed Checks:</h3>
+            <ul style="color: #d32f2f; margin: 0.5rem 0 1rem 1.5rem;">
+                ${results.failed.map(f => `<li>${f}</li>`).join('')}
+            </ul>
+
+            ${results.passed.length > 0 ? `
+                <h3 style="color: #666; margin-top: 1.5rem;">Passed Checks:</h3>
+                <ul style="color: #4caf50; margin: 0.5rem 0 1rem 1.5rem;">
+                    ${results.passed.map(p => `<li>${p}</li>`).join('')}
+                </ul>
+            ` : ''}
+
+            <p style="margin-top: 1.5rem; padding: 1rem; background: #f5f5f5; border-radius: 4px;">
+                <strong>Recommended browsers:</strong><br>
+                Chrome 90+, Firefox 88+, Safari 14+, Edge 90+
+            </p>
+        </div>
+    `;
+}
diff --git a/static/js/state.js b/static/js/state.js
new file mode 100644
index 0000000..4594b73
--- /dev/null
+++ b/static/js/state.js
@@ -0,0 +1,92 @@
+export default class AppState {
+    constructor(initialState = {}, reducers = {}) {
+        this._state = { ...initialState };
+        this._reducers = reducers;
+        this._subscribers = new Set();
+        this._middlewares = [];
+        this._history = [{ ...initialState }];
+        this._historyIndex = 0;
+    }
+
+    use(middleware) {
+        this._middlewares.push(middleware);
+        return this;
+    }
+
+    subscribe(callback) {
+        this._subscribers.add(callback);
+        return () => this._subscribers.delete(callback);
+    }
+
+    getState() {
+        return { ...this._state };
+    }
+
+    setState(updates) {
+        const prevState = this.getState();
+        this._state = { ...this._state, ...updates };
+
+        this._history = this._history.slice(0, this._historyIndex + 1);
+        this._history.push({ ...this._state });
+        this._historyIndex++;
+
+        this._notifySubscribers(prevState, { type: 'STATE_UPDATE', payload: updates });
+    }
+
+    async dispatch(action) {
+        let processedAction = action;
+
+        for (const middleware of this._middlewares) {
+            processedAction = await middleware(processedAction, this.getState(), this);
+            if (!processedAction) return;
+        }
+
+        const { type, payload } = processedAction;
+        const reducer = this._reducers[type];
+
+        if (!reducer) {
+            console.warn(`No reducer for action: ${type}`);
+            return;
+        }
+
+        try {
+            const prevState = this.getState();
+            const newState = reducer(prevState, payload);
+            this._state = { ...newState };
+
+            this._history = this._history.slice(0, this._historyIndex + 1);
+            this._history.push({ ...this._state });
+            this._historyIndex++;
+
+            this._notifySubscribers(prevState, processedAction);
+        } catch (error) {
+            console.error(`Reducer error for ${type}:`, error);
+        }
+    }
+
+    undo() {
+        if (this._historyIndex > 0) {
+            this._historyIndex--;
+            this._state = { ...this._history[this._historyIndex] };
+            this._notifySubscribers(null, { type: 'UNDO' });
+        }
+    }
+
+    redo() {
+        if (this._historyIndex < this._history.length - 1) {
+            this._historyIndex++;
+            this._state = { ...this._history[this._historyIndex] };
+            this._notifySubscribers(null, { type: 'REDO' });
+        }
+    }
+
+    _notifySubscribers(prevState, action) {
+        this._subscribers.forEach(callback => {
+            try {
+                callback(this.getState(), prevState, action);
+            } catch (error) {
+                console.error('Subscriber error:', error);
+            }
+        });
+    }
+}
diff --git a/static/js/utils.js b/static/js/utils.js
new file mode 100644
index 0000000..410f5a9
--- /dev/null
+++ b/static/js/utils.js
@@ -0,0 +1,71 @@
+export function debounce(fn, delay = 300) {
+    let timeoutId;
+    return function (...args) {
+        clearTimeout(timeoutId);
+        timeoutId = setTimeout(() => fn.apply(this, args), delay);
+    };
+}
+
+export function throttle(fn, delay = 300) {
+    let lastCall = 0;
+    let timeoutId;
+
+    return function (...args) {
+        const now = Date.now();
+
+        if (now - lastCall >= delay) {
+            lastCall = now;
+            fn.apply(this, args);
+        } else {
+            clearTimeout(timeoutId);
+            timeoutId = setTimeout(() => {
+                lastCall = Date.now();
+                fn.apply(this, args);
+            }, delay - (now - lastCall));
+        }
+    };
+}
+
+export function once(fn) {
+    let called = false;
+    return function (...args) {
+        if (!called) {
+            called = true;
+            return fn.apply(this, args);
+        }
+    };
+}
+
+export function compose(...fns) {
+    return (value) => fns.reduceRight((acc, fn) => fn(acc), value);
+}
+
+export function pipe(...fns) {
+    return (value) => fns.reduce((acc, fn) => fn(acc), value);
+}
+
+export async function retry(fn, maxAttempts = 3, delay = 1000) {
+    for (let attempt = 1; attempt <= maxAttempts; attempt++) {
+        try {
+            return await fn();
+        } catch (error) {
+            if (attempt === maxAttempts) throw error;
+            await new Promise(resolve => setTimeout(resolve, delay * attempt));
+        }
+    }
+}
+
+export function deepClone(obj) {
+    if (obj === null || typeof obj !== 'object') return obj;
+    if (obj instanceof Date) return new Date(obj.getTime());
+    if (obj instanceof Array) return obj.map(item => deepClone(item));
+    if (obj instanceof Object) {
+        const cloned = {};
+        for (const key in obj) {
+            if (obj.hasOwnProperty(key)) {
+                cloned[key] = deepClone(obj[key]);
+            }
+        }
+        return cloned;
+    }
+}
diff --git a/tests/e2e/conftest.py b/tests/e2e/conftest.py
index 1b32b11..ac3c7a8 100644
--- a/tests/e2e/conftest.py
+++ b/tests/e2e/conftest.py
@@ -1,7 +1,7 @@
 import pytest
 import pytest_asyncio
 import asyncio
-from playwright.async_api import async_playwright
+from playwright.async_api import async_playwright, Page, expect
 
 @pytest.fixture(scope="session")
 def event_loop():
@@ -35,4 +35,33 @@ async def page(context):
 
 @pytest.fixture
 def base_url():
-    return "http://localhost:8000"
+    return "http://localhost:9004"
+
+@pytest_asyncio.fixture(scope="function", autouse=True)
+async def login(page: Page, base_url):
+    print(f"Navigating to base_url: {base_url}")
+    await page.goto(f"{base_url}/")
+    await page.screenshot(path="01_initial_page.png")
+
+    # If already logged in, log out first to ensure a clean state
+    if await page.locator('a:has-text("Logout")').is_visible():
+        await page.click('a:has-text("Logout")')
+        await page.screenshot(path="02_after_logout.png")
+
+    # Now, proceed with login or registration
+    login_form = page.locator('#login-form:visible')
+    if await login_form.count() > 0:
+        await login_form.locator('input[name="username"]').fill('billingtest')
+        await login_form.locator('input[name="password"]').fill('password123')
+        await page.screenshot(path="03_before_login_click.png")
+        await expect(page.locator('h2:has-text("Files")')).to_be_visible(timeout=10000)
+    else:
+        # If no login form, try to register
+        await page.click('text=Sign Up')
+        register_form = page.locator('#register-form:visible')
+        await register_form.locator('input[name="username"]').fill('billingtest')
+        await register_form.locator('input[name="email"]').fill('billingtest@example.com')
+        await register_form.locator('input[name="password"]').fill('password123')
+        await page.screenshot(path="05_before_register_click.png")
+        await register_form.locator('button[type="submit"]').click()
+        await expect(page.locator('h1:has-text("My Files")')).to_be_visible(timeout=10000)
\ No newline at end of file