feat: complete subscription billing system phases 6-10

Phase 6 - Database-driven tiers:
- Update subscription_service to query database first with legacy fallback
- Add get_tier_info() db parameter and _get_tier_from_legacy() method

Phase 7 - Platform health integration:
- Add get_subscription_capacity() for theoretical vs actual capacity
- Include subscription capacity in full health report

Phase 8 - Background subscription tasks:
- Add reset_period_counters() for billing period resets
- Add check_trial_expirations() for trial management
- Add sync_stripe_status() for Stripe synchronization
- Add cleanup_stale_subscriptions() for maintenance
- Add capture_capacity_snapshot() for daily metrics

Phase 10 - Capacity planning & forecasting:
- Add CapacitySnapshot model for historical tracking
- Create capacity_forecast_service with growth trends
- Add /subscription-capacity, /trends, /recommendations endpoints
- Add /snapshot endpoint for manual captures

Also includes billing API enhancements from phase 4:
- Add upcoming-invoice, change-tier, addon purchase/cancel endpoints
- Add UsageSummary schema for billing page
- Enhance billing.js with addon management functions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

alembic/versions/l0a1b2c3d4e5_add_capacity_snapshots_table.py

@@ -0,0 +1,65 @@
+"""Add capacity_snapshots table
+
+Revision ID: l0a1b2c3d4e5
+Revises: k9f0a1b2c3d4
+Create Date: 2025-12-26
+
+Adds table for tracking daily platform capacity metrics for growth forecasting.
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = "l0a1b2c3d4e5"
+down_revision = "k9f0a1b2c3d4"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "capacity_snapshots",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("snapshot_date", sa.DateTime(timezone=True), nullable=False),
+        # Vendor metrics
+        sa.Column("total_vendors", sa.Integer(), nullable=False, server_default="0"),
+        sa.Column("active_vendors", sa.Integer(), nullable=False, server_default="0"),
+        sa.Column("trial_vendors", sa.Integer(), nullable=False, server_default="0"),
+        # Subscription metrics
+        sa.Column("total_subscriptions", sa.Integer(), nullable=False, server_default="0"),
+        sa.Column("active_subscriptions", sa.Integer(), nullable=False, server_default="0"),
+        # Resource metrics
+        sa.Column("total_products", sa.Integer(), nullable=False, server_default="0"),
+        sa.Column("total_orders_month", sa.Integer(), nullable=False, server_default="0"),
+        sa.Column("total_team_members", sa.Integer(), nullable=False, server_default="0"),
+        # Storage metrics
+        sa.Column("storage_used_gb", sa.Numeric(10, 2), nullable=False, server_default="0"),
+        sa.Column("db_size_mb", sa.Numeric(10, 2), nullable=False, server_default="0"),
+        # Capacity metrics
+        sa.Column("theoretical_products_limit", sa.Integer(), nullable=True),
+        sa.Column("theoretical_orders_limit", sa.Integer(), nullable=True),
+        sa.Column("theoretical_team_limit", sa.Integer(), nullable=True),
+        # Tier distribution
+        sa.Column("tier_distribution", sa.JSON(), nullable=True),
+        # Performance metrics
+        sa.Column("avg_response_ms", sa.Integer(), nullable=True),
+        sa.Column("peak_cpu_percent", sa.Numeric(5, 2), nullable=True),
+        sa.Column("peak_memory_percent", sa.Numeric(5, 2), nullable=True),
+        # Timestamps
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        # Primary key
+        sa.PrimaryKeyConstraint("id"),
+    )
+
+    # Create indexes
+    op.create_index("ix_capacity_snapshots_id", "capacity_snapshots", ["id"], unique=False)
+    op.create_index("ix_capacity_snapshots_date", "capacity_snapshots", ["snapshot_date"], unique=True)
+
+
+def downgrade() -> None:
+    op.drop_index("ix_capacity_snapshots_date", table_name="capacity_snapshots")
+    op.drop_index("ix_capacity_snapshots_id", table_name="capacity_snapshots")
+    op.drop_table("capacity_snapshots")

app/api/v1/admin/platform_health.py

@@ -144,3 +144,71 @@ async def get_capacity_metrics(
     """Get capacity-focused metrics for planning."""
     metrics = platform_health_service.get_capacity_metrics(db)
     return CapacityMetricsResponse(**metrics)
+
+
+@router.get("/subscription-capacity")
+async def get_subscription_capacity(
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+):
+    """
+    Get subscription-based capacity metrics.
+
+    Shows theoretical vs actual capacity based on all vendor subscriptions.
+    """
+    return platform_health_service.get_subscription_capacity(db)
+
+
+@router.get("/trends")
+async def get_growth_trends(
+    days: int = 30,
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+):
+    """
+    Get growth trends over the specified period.
+
+    Returns growth rates and projections for key metrics.
+    """
+    from app.services.capacity_forecast_service import capacity_forecast_service
+
+    return capacity_forecast_service.get_growth_trends(db, days=days)
+
+
+@router.get("/recommendations")
+async def get_scaling_recommendations(
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+):
+    """
+    Get scaling recommendations based on current capacity and growth.
+
+    Returns prioritized list of recommendations.
+    """
+    from app.services.capacity_forecast_service import capacity_forecast_service
+
+    return capacity_forecast_service.get_scaling_recommendations(db)
+
+
+@router.post("/snapshot")
+async def capture_snapshot(
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+):
+    """
+    Manually capture a capacity snapshot.
+
+    Normally run automatically by daily background job.
+    """
+    from app.services.capacity_forecast_service import capacity_forecast_service
+
+    snapshot = capacity_forecast_service.capture_daily_snapshot(db)
+    db.commit()
+
+    return {
+        "id": snapshot.id,
+        "snapshot_date": snapshot.snapshot_date.isoformat(),
+        "total_vendors": snapshot.total_vendors,
+        "total_products": snapshot.total_products,
+        "message": "Snapshot captured successfully",
+    }

app/api/v1/admin/subscriptions.py

@@ -12,12 +12,16 @@ Provides endpoints for platform administrators to manage:
 import logging
 
 from fastapi import APIRouter, Depends, Path, Query
+from sqlalchemy import func
 from sqlalchemy.orm import Session
 
 from app.api.deps import get_current_admin_api
 from app.core.database import get_db
 from app.services.admin_subscription_service import admin_subscription_service
+from models.database.product import Product
 from models.database.user import User
+from models.database.vendor import VendorUser
+from app.services.subscription_service import subscription_service
 from models.schema.billing import (
     BillingHistoryListResponse,
     BillingHistoryWithVendor,
@@ -26,6 +30,7 @@ from models.schema.billing import (
     SubscriptionTierListResponse,
     SubscriptionTierResponse,
     SubscriptionTierUpdate,
+    VendorSubscriptionCreate,
     VendorSubscriptionListResponse,
     VendorSubscriptionResponse,
     VendorSubscriptionUpdate,
@@ -144,9 +149,6 @@ def list_vendor_subscriptions(
             **VendorSubscriptionResponse.model_validate(sub).model_dump(),
             "vendor_name": vendor.name,
             "vendor_code": vendor.subdomain,
-            "orders_limit": sub.orders_limit,
-            "products_limit": sub.products_limit,
-            "team_members_limit": sub.team_members_limit,
         }
         subscriptions.append(VendorSubscriptionWithVendor(**sub_dict))
 
@@ -231,6 +233,73 @@ def list_billing_history(
 # ============================================================================
 
 
+@router.post("/{vendor_id}", response_model=VendorSubscriptionWithVendor, status_code=201)
+def create_vendor_subscription(
+    create_data: VendorSubscriptionCreate,
+    vendor_id: int = Path(..., description="Vendor ID"),
+    current_user: User = Depends(get_current_admin_api),
+    db: Session = Depends(get_db),
+):
+    """
+    Create a subscription for a vendor.
+
+    Creates a new subscription with the specified tier and status.
+    Defaults to Essential tier with trial status.
+    """
+    from models.database.vendor import Vendor
+
+    # Verify vendor exists
+    vendor = db.query(Vendor).filter(Vendor.id == vendor_id).first()
+    if not vendor:
+        from app.exceptions import ResourceNotFoundException
+        raise ResourceNotFoundException("Vendor", str(vendor_id))
+
+    # Create subscription using the subscription service
+    sub = subscription_service.get_or_create_subscription(
+        db,
+        vendor_id=vendor_id,
+        tier=create_data.tier,
+        trial_days=create_data.trial_days,
+    )
+
+    # Update status if not trial
+    if create_data.status != "trial":
+        sub.status = create_data.status
+
+    sub.is_annual = create_data.is_annual
+
+    db.commit()
+    db.refresh(sub)
+
+    # Get usage counts
+    products_count = (
+        db.query(func.count(Product.id))
+        .filter(Product.vendor_id == vendor_id)
+        .scalar()
+        or 0
+    )
+
+    team_count = (
+        db.query(func.count(VendorUser.id))
+        .filter(
+            VendorUser.vendor_id == vendor_id,
+            VendorUser.is_active == True,  # noqa: E712
+        )
+        .scalar()
+        or 0
+    )
+
+    logger.info(f"Admin created subscription for vendor {vendor_id}: tier={create_data.tier}")
+
+    return VendorSubscriptionWithVendor(
+        **VendorSubscriptionResponse.model_validate(sub).model_dump(),
+        vendor_name=vendor.name,
+        vendor_code=vendor.subdomain,
+        products_count=products_count,
+        team_count=team_count,
+    )
+
+
 @router.get("/{vendor_id}", response_model=VendorSubscriptionWithVendor)
 def get_vendor_subscription(
     vendor_id: int = Path(..., description="Vendor ID"),
@@ -240,13 +309,30 @@ def get_vendor_subscription(
     """Get subscription details for a specific vendor."""
     sub, vendor = admin_subscription_service.get_subscription(db, vendor_id)
 
+    # Get usage counts
+    products_count = (
+        db.query(func.count(Product.id))
+        .filter(Product.vendor_id == vendor_id)
+        .scalar()
+        or 0
+    )
+
+    team_count = (
+        db.query(func.count(VendorUser.id))
+        .filter(
+            VendorUser.vendor_id == vendor_id,
+            VendorUser.is_active == True,  # noqa: E712
+        )
+        .scalar()
+        or 0
+    )
+
     return VendorSubscriptionWithVendor(
         **VendorSubscriptionResponse.model_validate(sub).model_dump(),
         vendor_name=vendor.name,
         vendor_code=vendor.subdomain,
-        orders_limit=sub.orders_limit,
-        products_limit=sub.products_limit,
-        team_members_limit=sub.team_members_limit,
+        products_count=products_count,
+        team_count=team_count,
     )
 
 
@@ -271,11 +357,28 @@ def update_vendor_subscription(
     db.commit()
     db.refresh(sub)
 
+    # Get usage counts
+    products_count = (
+        db.query(func.count(Product.id))
+        .filter(Product.vendor_id == vendor_id)
+        .scalar()
+        or 0
+    )
+
+    team_count = (
+        db.query(func.count(VendorUser.id))
+        .filter(
+            VendorUser.vendor_id == vendor_id,
+            VendorUser.is_active == True,  # noqa: E712
+        )
+        .scalar()
+        or 0
+    )
+
     return VendorSubscriptionWithVendor(
         **VendorSubscriptionResponse.model_validate(sub).model_dump(),
         vendor_name=vendor.name,
         vendor_code=vendor.subdomain,
-        orders_limit=sub.orders_limit,
-        products_limit=sub.products_limit,
-        team_members_limit=sub.team_members_limit,
+        products_count=products_count,
+        team_count=team_count,
     )

app/api/v1/admin/vendor_products.py

@@ -19,6 +19,7 @@ from sqlalchemy.orm import Session
 
 from app.api.deps import get_current_admin_api
 from app.core.database import get_db
+from app.services.subscription_service import subscription_service
 from app.services.vendor_product_service import vendor_product_service
 from models.database.user import User
 from models.schema.vendor_product import (
@@ -119,6 +120,9 @@ def create_vendor_product(
     current_admin: User = Depends(get_current_admin_api),
 ):
     """Create a new vendor product."""
+    # Check product limit before creating
+    subscription_service.check_product_limit(db, data.vendor_id)
+
     product = vendor_product_service.create_product(db, data.model_dump())
     db.commit()  # ✅ ARCH: Commit at API level for transaction control
     return VendorProductCreateResponse(

app/api/v1/vendor/billing.py

@@ -179,6 +179,37 @@ class CancelResponse(BaseModel):
     effective_date: str
 
 
+class UpcomingInvoiceResponse(BaseModel):
+    """Upcoming invoice preview."""
+
+    amount_due_cents: int
+    currency: str
+    next_payment_date: str | None = None
+    line_items: list[dict] = []
+
+
+class ChangeTierRequest(BaseModel):
+    """Request to change subscription tier."""
+
+    tier_code: str
+    is_annual: bool = False
+
+
+class ChangeTierResponse(BaseModel):
+    """Response for tier change."""
+
+    message: str
+    new_tier: str
+    effective_immediately: bool
+
+
+class AddOnCancelResponse(BaseModel):
+    """Response for add-on cancellation."""
+
+    message: str
+    addon_code: str
+
+
 # ============================================================================
 # Endpoints
 # ============================================================================
@@ -403,3 +434,92 @@ def reactivate_subscription(
     db.commit()
 
     return result
+
+
+@router.get("/upcoming-invoice", response_model=UpcomingInvoiceResponse)
+def get_upcoming_invoice(
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """Preview the upcoming invoice."""
+    vendor_id = current_user.token_vendor_id
+
+    result = billing_service.get_upcoming_invoice(db, vendor_id)
+
+    return UpcomingInvoiceResponse(
+        amount_due_cents=result.get("amount_due_cents", 0),
+        currency=result.get("currency", "EUR"),
+        next_payment_date=result.get("next_payment_date"),
+        line_items=result.get("line_items", []),
+    )
+
+
+@router.post("/change-tier", response_model=ChangeTierResponse)
+def change_tier(
+    request: ChangeTierRequest,
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """Change subscription tier (upgrade/downgrade)."""
+    vendor_id = current_user.token_vendor_id
+
+    result = billing_service.change_tier(
+        db=db,
+        vendor_id=vendor_id,
+        new_tier_code=request.tier_code,
+        is_annual=request.is_annual,
+    )
+    db.commit()
+
+    return ChangeTierResponse(
+        message=result["message"],
+        new_tier=result["new_tier"],
+        effective_immediately=result["effective_immediately"],
+    )
+
+
+@router.post("/addons/purchase")
+def purchase_addon(
+    request: AddOnPurchaseRequest,
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """Purchase an add-on product."""
+    vendor_id = current_user.token_vendor_id
+    vendor = billing_service.get_vendor(db, vendor_id)
+
+    # Build URLs
+    base_url = f"https://{settings.platform_domain}"
+    success_url = f"{base_url}/vendor/{vendor.vendor_code}/billing?addon_success=true"
+    cancel_url = f"{base_url}/vendor/{vendor.vendor_code}/billing?addon_cancelled=true"
+
+    result = billing_service.purchase_addon(
+        db=db,
+        vendor_id=vendor_id,
+        addon_code=request.addon_code,
+        domain_name=request.domain_name,
+        quantity=request.quantity,
+        success_url=success_url,
+        cancel_url=cancel_url,
+    )
+    db.commit()
+
+    return result
+
+
+@router.delete("/addons/{addon_id}", response_model=AddOnCancelResponse)
+def cancel_addon(
+    addon_id: int,
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """Cancel a purchased add-on."""
+    vendor_id = current_user.token_vendor_id
+
+    result = billing_service.cancel_addon(db, vendor_id, addon_id)
+    db.commit()
+
+    return AddOnCancelResponse(
+        message=result["message"],
+        addon_code=result["addon_code"],
+    )

app/services/admin_subscription_service.py

@@ -177,7 +177,7 @@ class AdminSubscriptionService:
         )
 
         if not result:
-            raise ResourceNotFoundException(f"Subscription for vendor {vendor_id} not found")
+            raise ResourceNotFoundException("Subscription", str(vendor_id))
 
         return result
 

app/services/billing_service.py

@@ -365,6 +365,224 @@ class BillingService:
 
         return {"message": "Subscription reactivated successfully"}
 
+    def get_upcoming_invoice(self, db: Session, vendor_id: int) -> dict:
+        """
+        Get upcoming invoice preview.
+
+        Returns:
+            Dict with amount_due_cents, currency, next_payment_date, line_items
+
+        Raises:
+            NoActiveSubscriptionError: If no subscription with customer ID
+        """
+        subscription = subscription_service.get_subscription(db, vendor_id)
+
+        if not subscription or not subscription.stripe_customer_id:
+            raise NoActiveSubscriptionError()
+
+        if not stripe_service.is_configured:
+            # Return empty preview if Stripe not configured
+            return {
+                "amount_due_cents": 0,
+                "currency": "EUR",
+                "next_payment_date": None,
+                "line_items": [],
+            }
+
+        invoice = stripe_service.get_upcoming_invoice(subscription.stripe_customer_id)
+
+        if not invoice:
+            return {
+                "amount_due_cents": 0,
+                "currency": "EUR",
+                "next_payment_date": None,
+                "line_items": [],
+            }
+
+        line_items = []
+        if invoice.lines and invoice.lines.data:
+            for line in invoice.lines.data:
+                line_items.append({
+                    "description": line.description or "",
+                    "amount_cents": line.amount,
+                    "quantity": line.quantity or 1,
+                })
+
+        return {
+            "amount_due_cents": invoice.amount_due,
+            "currency": invoice.currency.upper(),
+            "next_payment_date": datetime.fromtimestamp(invoice.next_payment_attempt).isoformat()
+            if invoice.next_payment_attempt
+            else None,
+            "line_items": line_items,
+        }
+
+    def change_tier(
+        self,
+        db: Session,
+        vendor_id: int,
+        new_tier_code: str,
+        is_annual: bool,
+    ) -> dict:
+        """
+        Change subscription tier (upgrade/downgrade).
+
+        Returns:
+            Dict with message, new_tier, effective_immediately
+
+        Raises:
+            TierNotFoundError: If tier doesn't exist
+            NoActiveSubscriptionError: If no subscription
+            StripePriceNotConfiguredError: If price not configured
+        """
+        subscription = subscription_service.get_subscription(db, vendor_id)
+
+        if not subscription or not subscription.stripe_subscription_id:
+            raise NoActiveSubscriptionError()
+
+        tier = self.get_tier_by_code(db, new_tier_code)
+
+        price_id = (
+            tier.stripe_price_annual_id
+            if is_annual and tier.stripe_price_annual_id
+            else tier.stripe_price_monthly_id
+        )
+
+        if not price_id:
+            raise StripePriceNotConfiguredError(new_tier_code)
+
+        # Update in Stripe
+        if stripe_service.is_configured:
+            stripe_service.update_subscription(
+                subscription_id=subscription.stripe_subscription_id,
+                new_price_id=price_id,
+            )
+
+        # Update local subscription
+        old_tier = subscription.tier
+        subscription.tier = new_tier_code
+        subscription.tier_id = tier.id
+        subscription.is_annual = is_annual
+        subscription.updated_at = datetime.utcnow()
+
+        is_upgrade = self._is_upgrade(db, old_tier, new_tier_code)
+
+        return {
+            "message": f"Subscription {'upgraded' if is_upgrade else 'changed'} to {tier.name}",
+            "new_tier": new_tier_code,
+            "effective_immediately": True,
+        }
+
+    def _is_upgrade(self, db: Session, old_tier: str, new_tier: str) -> bool:
+        """Check if tier change is an upgrade."""
+        old = db.query(SubscriptionTier).filter(SubscriptionTier.code == old_tier).first()
+        new = db.query(SubscriptionTier).filter(SubscriptionTier.code == new_tier).first()
+
+        if not old or not new:
+            return False
+
+        return new.display_order > old.display_order
+
+    def purchase_addon(
+        self,
+        db: Session,
+        vendor_id: int,
+        addon_code: str,
+        domain_name: str | None,
+        quantity: int,
+        success_url: str,
+        cancel_url: str,
+    ) -> dict:
+        """
+        Create checkout session for add-on purchase.
+
+        Returns:
+            Dict with checkout_url and session_id
+
+        Raises:
+            PaymentSystemNotConfiguredError: If Stripe not configured
+            AddonNotFoundError: If addon doesn't exist
+        """
+        if not stripe_service.is_configured:
+            raise PaymentSystemNotConfiguredError()
+
+        addon = (
+            db.query(AddOnProduct)
+            .filter(
+                AddOnProduct.code == addon_code,
+                AddOnProduct.is_active == True,  # noqa: E712
+            )
+            .first()
+        )
+
+        if not addon:
+            raise BillingServiceError(f"Add-on '{addon_code}' not found")
+
+        if not addon.stripe_price_id:
+            raise BillingServiceError(f"Stripe price not configured for add-on '{addon_code}'")
+
+        vendor = self.get_vendor(db, vendor_id)
+        subscription = subscription_service.get_or_create_subscription(db, vendor_id)
+
+        # Create checkout session for add-on
+        session = stripe_service.create_checkout_session(
+            db=db,
+            vendor=vendor,
+            price_id=addon.stripe_price_id,
+            success_url=success_url,
+            cancel_url=cancel_url,
+            quantity=quantity,
+            metadata={
+                "addon_code": addon_code,
+                "domain_name": domain_name or "",
+            },
+        )
+
+        return {
+            "checkout_url": session.url,
+            "session_id": session.id,
+        }
+
+    def cancel_addon(self, db: Session, vendor_id: int, addon_id: int) -> dict:
+        """
+        Cancel a purchased add-on.
+
+        Returns:
+            Dict with message and addon_code
+
+        Raises:
+            BillingServiceError: If addon not found or not owned by vendor
+        """
+        vendor_addon = (
+            db.query(VendorAddOn)
+            .filter(
+                VendorAddOn.id == addon_id,
+                VendorAddOn.vendor_id == vendor_id,
+            )
+            .first()
+        )
+
+        if not vendor_addon:
+            raise BillingServiceError("Add-on not found")
+
+        addon_code = vendor_addon.addon_product.code
+
+        # Cancel in Stripe if applicable
+        if stripe_service.is_configured and vendor_addon.stripe_subscription_item_id:
+            try:
+                stripe_service.cancel_subscription_item(vendor_addon.stripe_subscription_item_id)
+            except Exception as e:
+                logger.warning(f"Failed to cancel addon in Stripe: {e}")
+
+        # Mark as cancelled
+        vendor_addon.status = "cancelled"
+        vendor_addon.cancelled_at = datetime.utcnow()
+
+        return {
+            "message": "Add-on cancelled successfully",
+            "addon_code": addon_code,
+        }
+
 
 # Create service instance
 billing_service = BillingService()

app/services/capacity_forecast_service.py

@@ -0,0 +1,321 @@
+# app/services/capacity_forecast_service.py
+"""
+Capacity forecasting service for growth trends and scaling recommendations.
+
+Provides:
+- Historical capacity trend analysis
+- Growth rate calculations
+- Days-until-threshold projections
+- Scaling recommendations based on growth patterns
+"""
+
+import logging
+from datetime import UTC, datetime, timedelta
+from decimal import Decimal
+
+from sqlalchemy import func
+from sqlalchemy.orm import Session
+
+from models.database.product import Product
+from models.database.subscription import (
+    CapacitySnapshot,
+    SubscriptionStatus,
+    VendorSubscription,
+)
+from models.database.vendor import Vendor, VendorUser
+
+logger = logging.getLogger(__name__)
+
+
+# Scaling thresholds based on capacity-planning.md
+INFRASTRUCTURE_SCALING = [
+    {"name": "Starter", "max_vendors": 50, "max_products": 10_000, "cost_monthly": 30},
+    {"name": "Small", "max_vendors": 100, "max_products": 30_000, "cost_monthly": 80},
+    {"name": "Medium", "max_vendors": 300, "max_products": 100_000, "cost_monthly": 150},
+    {"name": "Large", "max_vendors": 500, "max_products": 250_000, "cost_monthly": 350},
+    {"name": "Scale", "max_vendors": 1000, "max_products": 500_000, "cost_monthly": 700},
+    {"name": "Enterprise", "max_vendors": None, "max_products": None, "cost_monthly": 1500},
+]
+
+
+class CapacityForecastService:
+    """Service for capacity forecasting and trend analysis."""
+
+    def capture_daily_snapshot(self, db: Session) -> CapacitySnapshot:
+        """
+        Capture a daily snapshot of platform capacity metrics.
+
+        Should be called by a daily background job.
+        """
+        from app.services.image_service import image_service
+        from app.services.platform_health_service import platform_health_service
+
+        now = datetime.now(UTC)
+        today = now.replace(hour=0, minute=0, second=0, microsecond=0)
+
+        # Check if snapshot already exists for today
+        existing = (
+            db.query(CapacitySnapshot)
+            .filter(CapacitySnapshot.snapshot_date == today)
+            .first()
+        )
+        if existing:
+            logger.info(f"Snapshot already exists for {today}")
+            return existing
+
+        # Gather metrics
+        total_vendors = db.query(func.count(Vendor.id)).scalar() or 0
+        active_vendors = (
+            db.query(func.count(Vendor.id))
+            .filter(Vendor.is_active == True)  # noqa: E712
+            .scalar()
+            or 0
+        )
+
+        # Subscription metrics
+        total_subs = db.query(func.count(VendorSubscription.id)).scalar() or 0
+        active_subs = (
+            db.query(func.count(VendorSubscription.id))
+            .filter(VendorSubscription.status.in_(["active", "trial"]))
+            .scalar()
+            or 0
+        )
+        trial_vendors = (
+            db.query(func.count(VendorSubscription.id))
+            .filter(VendorSubscription.status == SubscriptionStatus.TRIAL.value)
+            .scalar()
+            or 0
+        )
+
+        # Resource metrics
+        total_products = db.query(func.count(Product.id)).scalar() or 0
+        total_team = (
+            db.query(func.count(VendorUser.id))
+            .filter(VendorUser.is_active == True)  # noqa: E712
+            .scalar()
+            or 0
+        )
+
+        # Orders this month
+        start_of_month = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
+        total_orders = sum(
+            s.orders_this_period
+            for s in db.query(VendorSubscription).all()
+        )
+
+        # Storage metrics
+        try:
+            image_stats = image_service.get_storage_stats()
+            storage_gb = image_stats.get("total_size_gb", 0)
+        except Exception:
+            storage_gb = 0
+
+        try:
+            db_size = platform_health_service._get_database_size(db)
+        except Exception:
+            db_size = 0
+
+        # Theoretical capacity from subscriptions
+        capacity = platform_health_service.get_subscription_capacity(db)
+        theoretical_products = capacity["products"].get("theoretical_limit", 0)
+        theoretical_orders = capacity["orders_monthly"].get("theoretical_limit", 0)
+        theoretical_team = capacity["team_members"].get("theoretical_limit", 0)
+
+        # Tier distribution
+        tier_distribution = capacity.get("tier_distribution", {})
+
+        # Create snapshot
+        snapshot = CapacitySnapshot(
+            snapshot_date=today,
+            total_vendors=total_vendors,
+            active_vendors=active_vendors,
+            trial_vendors=trial_vendors,
+            total_subscriptions=total_subs,
+            active_subscriptions=active_subs,
+            total_products=total_products,
+            total_orders_month=total_orders,
+            total_team_members=total_team,
+            storage_used_gb=Decimal(str(storage_gb)),
+            db_size_mb=Decimal(str(db_size)),
+            theoretical_products_limit=theoretical_products,
+            theoretical_orders_limit=theoretical_orders,
+            theoretical_team_limit=theoretical_team,
+            tier_distribution=tier_distribution,
+        )
+
+        db.add(snapshot)
+        db.flush()
+        db.refresh(snapshot)
+
+        logger.info(f"Captured capacity snapshot for {today}")
+        return snapshot
+
+    def get_growth_trends(self, db: Session, days: int = 30) -> dict:
+        """
+        Calculate growth trends over the specified period.
+
+        Returns growth rates and projections for key metrics.
+        """
+        now = datetime.now(UTC)
+        start_date = now - timedelta(days=days)
+
+        # Get snapshots for the period
+        snapshots = (
+            db.query(CapacitySnapshot)
+            .filter(CapacitySnapshot.snapshot_date >= start_date)
+            .order_by(CapacitySnapshot.snapshot_date)
+            .all()
+        )
+
+        if len(snapshots) < 2:
+            return {
+                "period_days": days,
+                "snapshots_available": len(snapshots),
+                "trends": {},
+                "message": "Insufficient data for trend analysis",
+            }
+
+        first = snapshots[0]
+        last = snapshots[-1]
+        period_days = (last.snapshot_date - first.snapshot_date).days or 1
+
+        def calc_growth(metric: str) -> dict:
+            start_val = getattr(first, metric) or 0
+            end_val = getattr(last, metric) or 0
+            change = end_val - start_val
+
+            if start_val > 0:
+                growth_rate = (change / start_val) * 100
+                daily_rate = growth_rate / period_days
+                monthly_rate = daily_rate * 30
+            else:
+                growth_rate = 0 if end_val == 0 else 100
+                daily_rate = 0
+                monthly_rate = 0
+
+            return {
+                "start_value": start_val,
+                "current_value": end_val,
+                "change": change,
+                "growth_rate_percent": round(growth_rate, 2),
+                "daily_growth_rate": round(daily_rate, 3),
+                "monthly_projection": round(end_val * (1 + monthly_rate / 100), 0),
+            }
+
+        trends = {
+            "vendors": calc_growth("active_vendors"),
+            "products": calc_growth("total_products"),
+            "orders": calc_growth("total_orders_month"),
+            "team_members": calc_growth("total_team_members"),
+            "storage_gb": {
+                "start_value": float(first.storage_used_gb or 0),
+                "current_value": float(last.storage_used_gb or 0),
+                "change": float((last.storage_used_gb or 0) - (first.storage_used_gb or 0)),
+            },
+        }
+
+        return {
+            "period_days": period_days,
+            "snapshots_available": len(snapshots),
+            "start_date": first.snapshot_date.isoformat(),
+            "end_date": last.snapshot_date.isoformat(),
+            "trends": trends,
+        }
+
+    def get_scaling_recommendations(self, db: Session) -> list[dict]:
+        """
+        Generate scaling recommendations based on current capacity and growth.
+
+        Returns prioritized list of recommendations.
+        """
+        from app.services.platform_health_service import platform_health_service
+
+        recommendations = []
+
+        # Get current capacity
+        capacity = platform_health_service.get_subscription_capacity(db)
+        health = platform_health_service.get_full_health_report(db)
+        trends = self.get_growth_trends(db, days=30)
+
+        # Check product capacity
+        products = capacity["products"]
+        if products.get("utilization_percent") and products["utilization_percent"] > 80:
+            recommendations.append({
+                "category": "capacity",
+                "severity": "warning",
+                "title": "Product capacity approaching limit",
+                "description": f"Currently at {products['utilization_percent']:.0f}% of theoretical product capacity",
+                "action": "Consider upgrading vendor tiers or adding capacity",
+            })
+
+        # Check infrastructure tier
+        current_tier = health.get("infrastructure_tier", {})
+        next_trigger = health.get("next_tier_trigger")
+        if next_trigger:
+            recommendations.append({
+                "category": "infrastructure",
+                "severity": "info",
+                "title": f"Current tier: {current_tier.get('name', 'Unknown')}",
+                "description": f"Next upgrade trigger: {next_trigger}",
+                "action": "Monitor growth and plan for infrastructure scaling",
+            })
+
+        # Check growth rate
+        if trends.get("trends"):
+            vendor_growth = trends["trends"].get("vendors", {})
+            if vendor_growth.get("monthly_projection", 0) > 0:
+                monthly_rate = vendor_growth.get("growth_rate_percent", 0)
+                if monthly_rate > 20:
+                    recommendations.append({
+                        "category": "growth",
+                        "severity": "info",
+                        "title": "High vendor growth rate",
+                        "description": f"Vendor base growing at {monthly_rate:.1f}% over last 30 days",
+                        "action": "Ensure infrastructure can scale to meet demand",
+                    })
+
+        # Check storage
+        storage_percent = health.get("image_storage", {}).get("total_size_gb", 0)
+        if storage_percent > 800:  # 80% of 1TB
+            recommendations.append({
+                "category": "storage",
+                "severity": "warning",
+                "title": "Storage usage high",
+                "description": f"Image storage at {storage_percent:.1f} GB",
+                "action": "Plan for storage expansion or implement cleanup policies",
+            })
+
+        # Sort by severity
+        severity_order = {"critical": 0, "warning": 1, "info": 2}
+        recommendations.sort(key=lambda r: severity_order.get(r["severity"], 3))
+
+        return recommendations
+
+    def get_days_until_threshold(
+        self, db: Session, metric: str, threshold: int
+    ) -> int | None:
+        """
+        Calculate days until a metric reaches a threshold based on current growth.
+
+        Returns None if insufficient data or no growth.
+        """
+        trends = self.get_growth_trends(db, days=30)
+
+        if not trends.get("trends") or metric not in trends["trends"]:
+            return None
+
+        metric_data = trends["trends"][metric]
+        current = metric_data.get("current_value", 0)
+        daily_rate = metric_data.get("daily_growth_rate", 0)
+
+        if daily_rate <= 0 or current >= threshold:
+            return None
+
+        remaining = threshold - current
+        days = remaining / (current * daily_rate / 100) if current > 0 else None
+
+        return int(days) if days else None
+
+
+# Singleton instance
+capacity_forecast_service = CapacityForecastService()

app/services/platform_health_service.py

@@ -166,6 +166,101 @@ class PlatformHealthService:
             "active_vendors": active_vendors,
         }
 
+    def get_subscription_capacity(self, db: Session) -> dict:
+        """
+        Calculate theoretical capacity based on all vendor subscriptions.
+
+        Returns aggregated limits and current usage for capacity planning.
+        """
+        from models.database.subscription import VendorSubscription
+        from models.database.vendor import VendorUser
+
+        # Get all active subscriptions with their limits
+        subscriptions = (
+            db.query(VendorSubscription)
+            .filter(VendorSubscription.status.in_(["active", "trial"]))
+            .all()
+        )
+
+        # Aggregate theoretical limits
+        total_products_limit = 0
+        total_orders_limit = 0
+        total_team_limit = 0
+        unlimited_products = 0
+        unlimited_orders = 0
+        unlimited_team = 0
+
+        tier_distribution = {}
+
+        for sub in subscriptions:
+            # Track tier distribution
+            tier = sub.tier or "unknown"
+            tier_distribution[tier] = tier_distribution.get(tier, 0) + 1
+
+            # Aggregate limits
+            if sub.products_limit is None:
+                unlimited_products += 1
+            else:
+                total_products_limit += sub.products_limit
+
+            if sub.orders_limit is None:
+                unlimited_orders += 1
+            else:
+                total_orders_limit += sub.orders_limit
+
+            if sub.team_members_limit is None:
+                unlimited_team += 1
+            else:
+                total_team_limit += sub.team_members_limit
+
+        # Get actual usage
+        actual_products = db.query(func.count(Product.id)).scalar() or 0
+        actual_team = (
+            db.query(func.count(VendorUser.id))
+            .filter(VendorUser.is_active == True)  # noqa: E712
+            .scalar()
+            or 0
+        )
+
+        # Orders this period (aggregate across all subscriptions)
+        total_orders_used = sum(s.orders_this_period for s in subscriptions)
+
+        def calc_utilization(actual: int, limit: int, unlimited: int) -> dict:
+            if unlimited > 0:
+                # Some subscriptions have unlimited - can't calculate true %
+                return {
+                    "actual": actual,
+                    "theoretical_limit": limit,
+                    "unlimited_count": unlimited,
+                    "utilization_percent": None,
+                    "has_unlimited": True,
+                }
+            elif limit > 0:
+                return {
+                    "actual": actual,
+                    "theoretical_limit": limit,
+                    "unlimited_count": 0,
+                    "utilization_percent": round((actual / limit) * 100, 1),
+                    "headroom": limit - actual,
+                    "has_unlimited": False,
+                }
+            else:
+                return {
+                    "actual": actual,
+                    "theoretical_limit": 0,
+                    "unlimited_count": 0,
+                    "utilization_percent": 0,
+                    "has_unlimited": False,
+                }
+
+        return {
+            "total_subscriptions": len(subscriptions),
+            "tier_distribution": tier_distribution,
+            "products": calc_utilization(actual_products, total_products_limit, unlimited_products),
+            "orders_monthly": calc_utilization(total_orders_used, total_orders_limit, unlimited_orders),
+            "team_members": calc_utilization(actual_team, total_team_limit, unlimited_team),
+        }
+
     def get_full_health_report(self, db: Session) -> dict:
         """Get comprehensive platform health report."""
         # System metrics
@@ -177,6 +272,9 @@ class PlatformHealthService:
         # Image storage metrics
         image_storage = self.get_image_storage_metrics()
 
+        # Subscription capacity
+        subscription_capacity = self.get_subscription_capacity(db)
+
         # Calculate thresholds
         thresholds = self._calculate_thresholds(system, database, image_storage)
 
@@ -197,6 +295,7 @@ class PlatformHealthService:
             "system": system,
             "database": database,
             "image_storage": image_storage,
+            "subscription_capacity": subscription_capacity,
             "thresholds": thresholds,
             "recommendations": recommendations,
             "infrastructure_tier": tier,

app/services/stripe_service.py

@@ -251,6 +251,19 @@ class StripeService:
         logger.info(f"Reactivated Stripe subscription {subscription_id}")
         return subscription
 
+    def cancel_subscription_item(self, subscription_item_id: str) -> None:
+        """
+        Cancel a subscription item (used for add-ons).
+
+        Args:
+            subscription_item_id: Stripe subscription item ID
+        """
+        if not self.is_configured:
+            raise ValueError("Stripe is not configured")
+
+        stripe.SubscriptionItem.delete(subscription_item_id)
+        logger.info(f"Cancelled Stripe subscription item {subscription_item_id}")
+
     # =========================================================================
     # Checkout & Portal
     # =========================================================================
@@ -263,6 +276,8 @@ class StripeService:
         success_url: str,
         cancel_url: str,
         trial_days: int | None = None,
+        quantity: int = 1,
+        metadata: dict | None = None,
     ) -> stripe.checkout.Session:
         """
         Create a Stripe Checkout session for subscription signup.
@@ -274,6 +289,8 @@ class StripeService:
             success_url: URL to redirect on success
             cancel_url: URL to redirect on cancel
             trial_days: Optional trial period
+            quantity: Number of items (default 1)
+            metadata: Additional metadata to store
 
         Returns:
             Stripe Checkout Session object
@@ -311,16 +328,21 @@ class StripeService:
                 subscription.stripe_customer_id = customer_id
                 db.flush()
 
+        # Build metadata
+        session_metadata = {
+            "vendor_id": str(vendor.id),
+            "vendor_code": vendor.vendor_code,
+        }
+        if metadata:
+            session_metadata.update(metadata)
+
         session_data = {
             "customer": customer_id,
-            "line_items": [{"price": price_id, "quantity": 1}],
+            "line_items": [{"price": price_id, "quantity": quantity}],
             "mode": "subscription",
             "success_url": success_url,
             "cancel_url": cancel_url,
-            "metadata": {
-                "vendor_id": str(vendor.id),
-                "vendor_code": vendor.vendor_code,
-            },
+            "metadata": session_metadata,
         }
 
         if trial_days:

app/services/subscription_service.py

@@ -40,6 +40,7 @@ from models.schema.subscription import (
     SubscriptionUsage,
     TierInfo,
     TierLimits,
+    UsageSummary,
 )
 
 logger = logging.getLogger(__name__)
@@ -79,8 +80,35 @@ class SubscriptionService:
     # Tier Information
     # =========================================================================
 
-    def get_tier_info(self, tier_code: str) -> TierInfo:
-        """Get full tier information."""
+    def get_tier_info(self, tier_code: str, db: Session | None = None) -> TierInfo:
+        """
+        Get full tier information.
+
+        Queries database if db session provided, otherwise falls back to TIER_LIMITS.
+        """
+        # Try database first if session provided
+        if db is not None:
+            db_tier = self.get_tier_by_code(db, tier_code)
+            if db_tier:
+                return TierInfo(
+                    code=db_tier.code,
+                    name=db_tier.name,
+                    price_monthly_cents=db_tier.price_monthly_cents,
+                    price_annual_cents=db_tier.price_annual_cents,
+                    limits=TierLimits(
+                        orders_per_month=db_tier.orders_per_month,
+                        products_limit=db_tier.products_limit,
+                        team_members=db_tier.team_members,
+                        order_history_months=db_tier.order_history_months,
+                    ),
+                    features=db_tier.features or [],
+                )
+
+        # Fallback to hardcoded TIER_LIMITS
+        return self._get_tier_from_legacy(tier_code)
+
+    def _get_tier_from_legacy(self, tier_code: str) -> TierInfo:
+        """Get tier info from hardcoded TIER_LIMITS (fallback)."""
         try:
             tier = TierCode(tier_code)
         except ValueError:
@@ -101,10 +129,43 @@ class SubscriptionService:
             features=limits.get("features", []),
         )
 
-    def get_all_tiers(self) -> list[TierInfo]:
-        """Get information for all tiers."""
+    def get_all_tiers(self, db: Session | None = None) -> list[TierInfo]:
+        """
+        Get information for all tiers.
+
+        Queries database if db session provided, otherwise falls back to TIER_LIMITS.
+        """
+        if db is not None:
+            db_tiers = (
+                db.query(SubscriptionTier)
+                .filter(
+                    SubscriptionTier.is_active == True,  # noqa: E712
+                    SubscriptionTier.is_public == True,  # noqa: E712
+                )
+                .order_by(SubscriptionTier.display_order)
+                .all()
+            )
+            if db_tiers:
+                return [
+                    TierInfo(
+                        code=t.code,
+                        name=t.name,
+                        price_monthly_cents=t.price_monthly_cents,
+                        price_annual_cents=t.price_annual_cents,
+                        limits=TierLimits(
+                            orders_per_month=t.orders_per_month,
+                            products_limit=t.products_limit,
+                            team_members=t.team_members,
+                            order_history_months=t.order_history_months,
+                        ),
+                        features=t.features or [],
+                    )
+                    for t in db_tiers
+                ]
+
+        # Fallback to hardcoded
         return [
-            self.get_tier_info(tier.value)
+            self._get_tier_from_legacy(tier.value)
             for tier in TierCode
         ]
 
@@ -363,6 +424,47 @@ class SubscriptionService:
             team_members_percent_used=calc_percent(team_count, team_limit),
         )
 
+    def get_usage_summary(self, db: Session, vendor_id: int) -> UsageSummary:
+        """Get usage summary for billing page display."""
+        subscription = self.get_or_create_subscription(db, vendor_id)
+
+        # Get actual counts
+        products_count = (
+            db.query(func.count(Product.id))
+            .filter(Product.vendor_id == vendor_id)
+            .scalar()
+            or 0
+        )
+
+        team_count = (
+            db.query(func.count(VendorUser.id))
+            .filter(VendorUser.vendor_id == vendor_id, VendorUser.is_active == True)
+            .scalar()
+            or 0
+        )
+
+        # Get limits
+        orders_limit = subscription.orders_limit
+        products_limit = subscription.products_limit
+        team_limit = subscription.team_members_limit
+
+        def calc_remaining(current: int, limit: int | None) -> int | None:
+            if limit is None:
+                return None
+            return max(0, limit - current)
+
+        return UsageSummary(
+            orders_this_period=subscription.orders_this_period,
+            orders_limit=orders_limit,
+            orders_remaining=calc_remaining(subscription.orders_this_period, orders_limit),
+            products_count=products_count,
+            products_limit=products_limit,
+            products_remaining=calc_remaining(products_count, products_limit),
+            team_count=team_count,
+            team_limit=team_limit,
+            team_remaining=calc_remaining(team_count, team_limit),
+        )
+
     def increment_order_count(self, db: Session, vendor_id: int) -> None:
         """
         Increment the order counter for the current period.

app/tasks/subscription_tasks.py

@@ -0,0 +1,318 @@
+# app/tasks/subscription_tasks.py
+"""
+Background tasks for subscription management.
+
+Provides scheduled tasks for:
+- Resetting period counters at billing period end
+- Expiring trials without payment methods
+- Syncing subscription status with Stripe
+- Capturing daily capacity snapshots
+"""
+
+import logging
+from datetime import UTC, datetime, timedelta
+
+from app.core.database import SessionLocal
+from app.services.stripe_service import stripe_service
+from models.database.subscription import SubscriptionStatus, VendorSubscription
+
+logger = logging.getLogger(__name__)
+
+
+async def reset_period_counters():
+    """
+    Reset order counters for subscriptions whose billing period has ended.
+
+    Should run daily. Resets orders_this_period to 0 and updates period dates.
+    """
+    db = SessionLocal()
+    now = datetime.now(UTC)
+    reset_count = 0
+
+    try:
+        # Find subscriptions where period has ended
+        expired_periods = (
+            db.query(VendorSubscription)
+            .filter(
+                VendorSubscription.period_end <= now,
+                VendorSubscription.status.in_(["active", "trial"]),
+            )
+            .all()
+        )
+
+        for subscription in expired_periods:
+            old_period_end = subscription.period_end
+
+            # Reset counters
+            subscription.orders_this_period = 0
+            subscription.orders_limit_reached_at = None
+
+            # Set new period dates
+            if subscription.is_annual:
+                subscription.period_start = now
+                subscription.period_end = now + timedelta(days=365)
+            else:
+                subscription.period_start = now
+                subscription.period_end = now + timedelta(days=30)
+
+            subscription.updated_at = now
+            reset_count += 1
+
+            logger.info(
+                f"Reset period counters for vendor {subscription.vendor_id}: "
+                f"old_period_end={old_period_end}, new_period_end={subscription.period_end}"
+            )
+
+        db.commit()
+        logger.info(f"Reset period counters for {reset_count} subscriptions")
+
+    except Exception as e:
+        logger.error(f"Error resetting period counters: {e}")
+        db.rollback()
+        raise
+    finally:
+        db.close()
+
+    return {"reset_count": reset_count}
+
+
+async def check_trial_expirations():
+    """
+    Check for expired trials and update their status.
+
+    Trials without a payment method are marked as expired.
+    Trials with a payment method transition to active.
+
+    Should run daily.
+    """
+    db = SessionLocal()
+    now = datetime.now(UTC)
+    expired_count = 0
+    activated_count = 0
+
+    try:
+        # Find expired trials
+        expired_trials = (
+            db.query(VendorSubscription)
+            .filter(
+                VendorSubscription.status == SubscriptionStatus.TRIAL.value,
+                VendorSubscription.trial_ends_at <= now,
+            )
+            .all()
+        )
+
+        for subscription in expired_trials:
+            if subscription.stripe_payment_method_id:
+                # Has payment method - activate
+                subscription.status = SubscriptionStatus.ACTIVE.value
+                activated_count += 1
+                logger.info(
+                    f"Activated subscription for vendor {subscription.vendor_id} "
+                    f"(trial ended with payment method)"
+                )
+            else:
+                # No payment method - expire
+                subscription.status = SubscriptionStatus.EXPIRED.value
+                expired_count += 1
+                logger.info(
+                    f"Expired trial for vendor {subscription.vendor_id} "
+                    f"(no payment method)"
+                )
+
+            subscription.updated_at = now
+
+        db.commit()
+        logger.info(
+            f"Trial expiration check: {expired_count} expired, {activated_count} activated"
+        )
+
+    except Exception as e:
+        logger.error(f"Error checking trial expirations: {e}")
+        db.rollback()
+        raise
+    finally:
+        db.close()
+
+    return {"expired_count": expired_count, "activated_count": activated_count}
+
+
+async def sync_stripe_status():
+    """
+    Sync subscription status with Stripe.
+
+    Fetches current status from Stripe and updates local records.
+    Handles cases where Stripe status differs from local status.
+
+    Should run hourly.
+    """
+    if not stripe_service.is_configured:
+        logger.warning("Stripe not configured, skipping sync")
+        return {"synced": 0, "skipped": True}
+
+    db = SessionLocal()
+    synced_count = 0
+    error_count = 0
+
+    try:
+        # Find subscriptions with Stripe IDs
+        subscriptions = (
+            db.query(VendorSubscription)
+            .filter(VendorSubscription.stripe_subscription_id.isnot(None))
+            .all()
+        )
+
+        for subscription in subscriptions:
+            try:
+                # Fetch from Stripe
+                stripe_sub = stripe_service.get_subscription(
+                    subscription.stripe_subscription_id
+                )
+
+                if not stripe_sub:
+                    logger.warning(
+                        f"Stripe subscription {subscription.stripe_subscription_id} "
+                        f"not found for vendor {subscription.vendor_id}"
+                    )
+                    continue
+
+                # Map Stripe status to local status
+                status_map = {
+                    "active": SubscriptionStatus.ACTIVE.value,
+                    "trialing": SubscriptionStatus.TRIAL.value,
+                    "past_due": SubscriptionStatus.PAST_DUE.value,
+                    "canceled": SubscriptionStatus.CANCELLED.value,
+                    "unpaid": SubscriptionStatus.PAST_DUE.value,
+                    "incomplete": SubscriptionStatus.TRIAL.value,
+                    "incomplete_expired": SubscriptionStatus.EXPIRED.value,
+                }
+
+                new_status = status_map.get(stripe_sub.status)
+                if new_status and new_status != subscription.status:
+                    old_status = subscription.status
+                    subscription.status = new_status
+                    subscription.updated_at = datetime.now(UTC)
+                    logger.info(
+                        f"Updated vendor {subscription.vendor_id} status: "
+                        f"{old_status} -> {new_status} (from Stripe)"
+                    )
+
+                # Update period dates from Stripe
+                if stripe_sub.current_period_start:
+                    subscription.period_start = datetime.fromtimestamp(
+                        stripe_sub.current_period_start, tz=UTC
+                    )
+                if stripe_sub.current_period_end:
+                    subscription.period_end = datetime.fromtimestamp(
+                        stripe_sub.current_period_end, tz=UTC
+                    )
+
+                # Update payment method
+                if stripe_sub.default_payment_method:
+                    subscription.stripe_payment_method_id = (
+                        stripe_sub.default_payment_method
+                        if isinstance(stripe_sub.default_payment_method, str)
+                        else stripe_sub.default_payment_method.id
+                    )
+
+                synced_count += 1
+
+            except Exception as e:
+                logger.error(
+                    f"Error syncing subscription {subscription.stripe_subscription_id}: {e}"
+                )
+                error_count += 1
+
+        db.commit()
+        logger.info(f"Stripe sync complete: {synced_count} synced, {error_count} errors")
+
+    except Exception as e:
+        logger.error(f"Error in Stripe sync task: {e}")
+        db.rollback()
+        raise
+    finally:
+        db.close()
+
+    return {"synced_count": synced_count, "error_count": error_count}
+
+
+async def cleanup_stale_subscriptions():
+    """
+    Clean up subscriptions in inconsistent states.
+
+    Handles edge cases like:
+    - Subscriptions stuck in processing
+    - Old cancelled subscriptions past their period end
+
+    Should run weekly.
+    """
+    db = SessionLocal()
+    now = datetime.now(UTC)
+    cleaned_count = 0
+
+    try:
+        # Find cancelled subscriptions past their period end
+        stale_cancelled = (
+            db.query(VendorSubscription)
+            .filter(
+                VendorSubscription.status == SubscriptionStatus.CANCELLED.value,
+                VendorSubscription.period_end < now - timedelta(days=30),
+            )
+            .all()
+        )
+
+        for subscription in stale_cancelled:
+            # Mark as expired (fully terminated)
+            subscription.status = SubscriptionStatus.EXPIRED.value
+            subscription.updated_at = now
+            cleaned_count += 1
+            logger.info(
+                f"Marked stale cancelled subscription as expired: "
+                f"vendor {subscription.vendor_id}"
+            )
+
+        db.commit()
+        logger.info(f"Cleaned up {cleaned_count} stale subscriptions")
+
+    except Exception as e:
+        logger.error(f"Error cleaning up stale subscriptions: {e}")
+        db.rollback()
+        raise
+    finally:
+        db.close()
+
+    return {"cleaned_count": cleaned_count}
+
+
+async def capture_capacity_snapshot():
+    """
+    Capture a daily snapshot of platform capacity metrics.
+
+    Used for growth trending and capacity forecasting.
+    Should run daily (e.g., at midnight).
+    """
+    from app.services.capacity_forecast_service import capacity_forecast_service
+
+    db = SessionLocal()
+
+    try:
+        snapshot = capacity_forecast_service.capture_daily_snapshot(db)
+        db.commit()
+
+        logger.info(
+            f"Captured capacity snapshot: {snapshot.total_vendors} vendors, "
+            f"{snapshot.total_products} products"
+        )
+
+        return {
+            "snapshot_id": snapshot.id,
+            "snapshot_date": snapshot.snapshot_date.isoformat(),
+            "total_vendors": snapshot.total_vendors,
+            "total_products": snapshot.total_products,
+        }
+
+    except Exception as e:
+        logger.error(f"Error capturing capacity snapshot: {e}")
+        db.rollback()
+        raise
+    finally:
+        db.close()

app/templates/admin/vendor-detail.html

@@ -106,6 +106,146 @@
         </div>
     </div>
 
+    <!-- Subscription Card -->
+    <div class="px-4 py-3 mb-6 bg-white rounded-lg shadow-md dark:bg-gray-800" x-show="subscription">
+        <div class="flex items-center justify-between mb-4">
+            <h3 class="text-lg font-semibold text-gray-700 dark:text-gray-200">
+                Subscription
+            </h3>
+            <button
+                @click="showSubscriptionModal = true"
+                class="flex items-center px-3 py-1.5 text-sm font-medium text-purple-600 hover:text-purple-700 dark:text-purple-400 dark:hover:text-purple-300">
+                <span x-html="$icon('edit', 'w-4 h-4 mr-1')"></span>
+                Edit
+            </button>
+        </div>
+
+        <!-- Tier and Status -->
+        <div class="flex flex-wrap items-center gap-4 mb-4">
+            <div class="flex items-center gap-2">
+                <span class="text-sm text-gray-600 dark:text-gray-400">Tier:</span>
+                <span class="px-2.5 py-0.5 text-sm font-medium rounded-full"
+                      :class="{
+                          'bg-gray-100 text-gray-800 dark:bg-gray-700 dark:text-gray-300': subscription?.tier === 'essential',
+                          'bg-blue-100 text-blue-800 dark:bg-blue-900 dark:text-blue-300': subscription?.tier === 'professional',
+                          'bg-purple-100 text-purple-800 dark:bg-purple-900 dark:text-purple-300': subscription?.tier === 'business',
+                          'bg-yellow-100 text-yellow-800 dark:bg-yellow-900 dark:text-yellow-300': subscription?.tier === 'enterprise'
+                      }"
+                      x-text="subscription?.tier ? subscription.tier.charAt(0).toUpperCase() + subscription.tier.slice(1) : '-'">
+                </span>
+            </div>
+            <div class="flex items-center gap-2">
+                <span class="text-sm text-gray-600 dark:text-gray-400">Status:</span>
+                <span class="px-2.5 py-0.5 text-sm font-medium rounded-full"
+                      :class="{
+                          'bg-green-100 text-green-800 dark:bg-green-900 dark:text-green-300': subscription?.status === 'active',
+                          'bg-blue-100 text-blue-800 dark:bg-blue-900 dark:text-blue-300': subscription?.status === 'trial',
+                          'bg-yellow-100 text-yellow-800 dark:bg-yellow-900 dark:text-yellow-300': subscription?.status === 'past_due',
+                          'bg-red-100 text-red-800 dark:bg-red-900 dark:text-red-300': subscription?.status === 'cancelled' || subscription?.status === 'expired'
+                      }"
+                      x-text="subscription?.status ? subscription.status.replace('_', ' ').charAt(0).toUpperCase() + subscription.status.slice(1) : '-'">
+                </span>
+            </div>
+            <template x-if="subscription?.is_annual">
+                <span class="px-2.5 py-0.5 text-xs font-medium text-purple-800 bg-purple-100 rounded-full dark:bg-purple-900 dark:text-purple-300">
+                    Annual
+                </span>
+            </template>
+        </div>
+
+        <!-- Period Info -->
+        <div class="flex flex-wrap gap-4 mb-4 text-sm">
+            <div>
+                <span class="text-gray-600 dark:text-gray-400">Period:</span>
+                <span class="ml-1 text-gray-700 dark:text-gray-300" x-text="formatDate(subscription?.period_start)"></span>
+                <span class="text-gray-400">→</span>
+                <span class="text-gray-700 dark:text-gray-300" x-text="formatDate(subscription?.period_end)"></span>
+            </div>
+            <template x-if="subscription?.trial_ends_at">
+                <div>
+                    <span class="text-gray-600 dark:text-gray-400">Trial ends:</span>
+                    <span class="ml-1 text-gray-700 dark:text-gray-300" x-text="formatDate(subscription?.trial_ends_at)"></span>
+                </div>
+            </template>
+        </div>
+
+        <!-- Usage Meters -->
+        <div class="grid gap-4 md:grid-cols-3">
+            <!-- Orders Usage -->
+            <div class="p-3 bg-gray-50 rounded-lg dark:bg-gray-700">
+                <div class="flex items-center justify-between mb-2">
+                    <span class="text-xs font-medium text-gray-600 dark:text-gray-400 uppercase">Orders This Period</span>
+                </div>
+                <div class="flex items-baseline gap-1">
+                    <span class="text-xl font-bold text-gray-700 dark:text-gray-200" x-text="subscription?.orders_this_period || 0"></span>
+                    <span class="text-sm text-gray-500 dark:text-gray-400">
+                        / <span x-text="subscription?.orders_limit || '∞'"></span>
+                    </span>
+                </div>
+                <div class="mt-2 h-1.5 bg-gray-200 rounded-full dark:bg-gray-600" x-show="subscription?.orders_limit">
+                    <div class="h-1.5 rounded-full transition-all"
+                         :class="getUsageBarColor(subscription?.orders_this_period, subscription?.orders_limit)"
+                         :style="`width: ${Math.min(100, (subscription?.orders_this_period / subscription?.orders_limit) * 100)}%`">
+                    </div>
+                </div>
+            </div>
+
+            <!-- Products Usage -->
+            <div class="p-3 bg-gray-50 rounded-lg dark:bg-gray-700">
+                <div class="flex items-center justify-between mb-2">
+                    <span class="text-xs font-medium text-gray-600 dark:text-gray-400 uppercase">Products</span>
+                </div>
+                <div class="flex items-baseline gap-1">
+                    <span class="text-xl font-bold text-gray-700 dark:text-gray-200" x-text="subscription?.products_count || 0"></span>
+                    <span class="text-sm text-gray-500 dark:text-gray-400">
+                        / <span x-text="subscription?.products_limit || '∞'"></span>
+                    </span>
+                </div>
+                <div class="mt-2 h-1.5 bg-gray-200 rounded-full dark:bg-gray-600" x-show="subscription?.products_limit">
+                    <div class="h-1.5 rounded-full transition-all"
+                         :class="getUsageBarColor(subscription?.products_count, subscription?.products_limit)"
+                         :style="`width: ${Math.min(100, (subscription?.products_count / subscription?.products_limit) * 100)}%`">
+                    </div>
+                </div>
+            </div>
+
+            <!-- Team Members Usage -->
+            <div class="p-3 bg-gray-50 rounded-lg dark:bg-gray-700">
+                <div class="flex items-center justify-between mb-2">
+                    <span class="text-xs font-medium text-gray-600 dark:text-gray-400 uppercase">Team Members</span>
+                </div>
+                <div class="flex items-baseline gap-1">
+                    <span class="text-xl font-bold text-gray-700 dark:text-gray-200" x-text="subscription?.team_count || 0"></span>
+                    <span class="text-sm text-gray-500 dark:text-gray-400">
+                        / <span x-text="subscription?.team_members_limit || '∞'"></span>
+                    </span>
+                </div>
+                <div class="mt-2 h-1.5 bg-gray-200 rounded-full dark:bg-gray-600" x-show="subscription?.team_members_limit">
+                    <div class="h-1.5 rounded-full transition-all"
+                         :class="getUsageBarColor(subscription?.team_count, subscription?.team_members_limit)"
+                         :style="`width: ${Math.min(100, (subscription?.team_count / subscription?.team_members_limit) * 100)}%`">
+                    </div>
+                </div>
+            </div>
+        </div>
+    </div>
+
+    <!-- No Subscription Notice -->
+    <div class="px-4 py-3 mb-6 bg-yellow-50 border border-yellow-200 rounded-lg dark:bg-yellow-900/20 dark:border-yellow-800" x-show="!subscription && !loading">
+        <div class="flex items-center gap-3">
+            <span x-html="$icon('exclamation', 'w-5 h-5 text-yellow-600 dark:text-yellow-400')"></span>
+            <div>
+                <p class="text-sm font-medium text-yellow-800 dark:text-yellow-200">No Subscription Found</p>
+                <p class="text-sm text-yellow-700 dark:text-yellow-300">This vendor doesn't have a subscription yet.</p>
+            </div>
+            <button
+                @click="createSubscription()"
+                class="ml-auto px-3 py-1.5 text-sm font-medium text-white bg-yellow-600 rounded-lg hover:bg-yellow-700">
+                Create Subscription
+            </button>
+        </div>
+    </div>
+
     <!-- Main Info Cards -->
     <div class="grid gap-6 mb-8 md:grid-cols-2">
         <!-- Basic Information -->

app/templates/admin/vendor-edit.html

@@ -86,7 +86,7 @@
                     </span>
                     <input
                         type="text"
-                        x-model="vendor.vendor_code"
+                        :value="vendor?.vendor_code || ''"
                         disabled
                         class="block w-full mt-1 text-sm bg-gray-100 border-gray-300 rounded-md dark:bg-gray-700 dark:text-gray-400 dark:border-gray-600 cursor-not-allowed"
                     >
@@ -171,7 +171,7 @@
                     </span>
                     <input
                         type="email"
-                        x-model="vendor.owner_email"
+                        :value="vendor?.owner_email || ''"
                         disabled
                         class="block w-full mt-1 text-sm bg-gray-100 border-gray-300 rounded-md dark:bg-gray-700 dark:text-gray-400 dark:border-gray-600 cursor-not-allowed"
                     >

app/templates/vendor/billing.html

@@ -37,6 +37,18 @@
     </div>
 </template>
 
+<template x-if="showAddonSuccessMessage">
+    <div class="mb-6 p-4 bg-green-100 border border-green-400 text-green-700 rounded-lg flex items-center justify-between">
+        <div class="flex items-center">
+            <span x-html="$icon('check-circle', 'w-5 h-5 mr-2')"></span>
+            <span>Add-on purchased successfully!</span>
+        </div>
+        <button @click="showAddonSuccessMessage = false" class="text-green-700 hover:text-green-900">
+            <span x-html="$icon('x-mark', 'w-5 h-5')"></span>
+        </button>
+    </div>
+</template>
+
 <!-- Loading State -->
 <template x-if="loading">
     <div class="flex justify-center items-center py-12">
@@ -314,18 +326,46 @@
      x-transition:leave-end="opacity-0"
      class="fixed inset-0 z-30 flex items-center justify-center overflow-auto bg-black bg-opacity-50"
      @click.self="showAddonsModal = false">
-    <div class="w-full max-w-2xl mx-4 bg-white dark:bg-gray-800 rounded-lg shadow-xl">
+    <div class="w-full max-w-2xl mx-4 bg-white dark:bg-gray-800 rounded-lg shadow-xl max-h-[90vh] overflow-hidden flex flex-col">
         <div class="flex items-center justify-between px-6 py-4 border-b dark:border-gray-700">
             <h3 class="text-lg font-semibold text-gray-700 dark:text-gray-200">Add-ons</h3>
             <button @click="showAddonsModal = false" class="text-gray-400 hover:text-gray-600">
                 <span x-html="$icon('x-mark', 'w-6 h-6')"></span>
             </button>
         </div>
-        <div class="p-6">
+        <div class="p-6 overflow-y-auto">
+            <!-- My Active Add-ons -->
+            <template x-if="myAddons.length > 0">
+                <div class="mb-6">
+                    <h4 class="text-sm font-semibold text-gray-600 dark:text-gray-400 mb-3 uppercase tracking-wide">Your Active Add-ons</h4>
+                    <div class="space-y-3">
+                        <template x-for="addon in myAddons.filter(a => a.status === 'active')" :key="addon.id">
+                            <div class="flex items-center justify-between p-4 bg-green-50 dark:bg-green-900/30 border border-green-200 dark:border-green-800 rounded-lg">
+                                <div>
+                                    <h4 class="font-medium text-gray-700 dark:text-gray-200" x-text="addon.addon_name"></h4>
+                                    <template x-if="addon.domain_name">
+                                        <p class="text-sm text-gray-500 dark:text-gray-400" x-text="addon.domain_name"></p>
+                                    </template>
+                                    <p class="text-xs text-gray-400 mt-1">
+                                        <span x-text="addon.period_end ? `Renews ${formatDate(addon.period_end)}` : 'Active'"></span>
+                                    </p>
+                                </div>
+                                <button @click="cancelAddon(addon)"
+                                        class="px-3 py-1 text-sm font-medium text-red-600 bg-red-100 rounded-lg hover:bg-red-200 dark:bg-red-900/50 dark:text-red-400">
+                                    Cancel
+                                </button>
+                            </div>
+                        </template>
+                    </div>
+                </div>
+            </template>
+
+            <!-- Available Add-ons -->
+            <h4 class="text-sm font-semibold text-gray-600 dark:text-gray-400 mb-3 uppercase tracking-wide">Available Add-ons</h4>
             <template x-if="addons.length === 0">
                 <p class="text-gray-500 text-center py-8">No add-ons available</p>
             </template>
-            <div class="space-y-4">
+            <div class="space-y-3">
                 <template x-for="addon in addons" :key="addon.id">
                     <div class="flex items-center justify-between p-4 bg-gray-50 dark:bg-gray-700 rounded-lg">
                         <div>
@@ -336,8 +376,22 @@
                                 <span x-text="`/${addon.billing_period}`"></span>
                             </p>
                         </div>
-                        <button class="px-4 py-2 text-sm font-medium text-purple-600 bg-purple-100 rounded-lg hover:bg-purple-200">
-                            Add
+                        <button @click="purchaseAddon(addon)"
+                                :disabled="isAddonPurchased(addon.code) || purchasingAddon === addon.code"
+                                :class="isAddonPurchased(addon.code) ? 'bg-gray-200 text-gray-500 cursor-not-allowed' : 'bg-purple-100 text-purple-600 hover:bg-purple-200'"
+                                class="px-4 py-2 text-sm font-medium rounded-lg transition-colors">
+                            <template x-if="purchasingAddon === addon.code">
+                                <span class="flex items-center">
+                                    <svg class="animate-spin -ml-1 mr-2 h-4 w-4" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24">
+                                        <circle class="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" stroke-width="4"></circle>
+                                        <path class="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"></path>
+                                    </svg>
+                                    Processing...
+                                </span>
+                            </template>
+                            <template x-if="purchasingAddon !== addon.code">
+                                <span x-text="isAddonPurchased(addon.code) ? 'Active' : 'Add'"></span>
+                            </template>
                         </button>
                     </div>
                 </template>

models/database/subscription.py

@@ -652,3 +652,61 @@ class VendorSubscription(Base, TimestampMixin):
         """Reset counters for new billing period."""
         self.orders_this_period = 0
         self.orders_limit_reached_at = None
+
+
+# ============================================================================
+# Capacity Planning
+# ============================================================================
+
+
+class CapacitySnapshot(Base, TimestampMixin):
+    """
+    Daily snapshot of platform capacity metrics.
+
+    Used for growth trending and capacity forecasting.
+    Captured daily by background job.
+    """
+
+    __tablename__ = "capacity_snapshots"
+
+    id = Column(Integer, primary_key=True, index=True)
+    snapshot_date = Column(DateTime(timezone=True), nullable=False, unique=True, index=True)
+
+    # Vendor metrics
+    total_vendors = Column(Integer, default=0, nullable=False)
+    active_vendors = Column(Integer, default=0, nullable=False)
+    trial_vendors = Column(Integer, default=0, nullable=False)
+
+    # Subscription metrics
+    total_subscriptions = Column(Integer, default=0, nullable=False)
+    active_subscriptions = Column(Integer, default=0, nullable=False)
+
+    # Resource metrics
+    total_products = Column(Integer, default=0, nullable=False)
+    total_orders_month = Column(Integer, default=0, nullable=False)
+    total_team_members = Column(Integer, default=0, nullable=False)
+
+    # Storage metrics
+    storage_used_gb = Column(Numeric(10, 2), default=0, nullable=False)
+    db_size_mb = Column(Numeric(10, 2), default=0, nullable=False)
+
+    # Capacity metrics (theoretical limits from subscriptions)
+    theoretical_products_limit = Column(Integer, nullable=True)
+    theoretical_orders_limit = Column(Integer, nullable=True)
+    theoretical_team_limit = Column(Integer, nullable=True)
+
+    # Tier distribution (JSON: {"essential": 10, "professional": 5, ...})
+    tier_distribution = Column(JSON, nullable=True)
+
+    # Performance metrics
+    avg_response_ms = Column(Integer, nullable=True)
+    peak_cpu_percent = Column(Numeric(5, 2), nullable=True)
+    peak_memory_percent = Column(Numeric(5, 2), nullable=True)
+
+    # Indexes
+    __table_args__ = (
+        Index("ix_capacity_snapshots_date", "snapshot_date"),
+    )
+
+    def __repr__(self) -> str:
+        return f"<CapacitySnapshot(date={self.snapshot_date}, vendors={self.total_vendors})>"

models/schema/billing.py

@@ -146,6 +146,10 @@ class VendorSubscriptionWithVendor(VendorSubscriptionResponse):
     vendor_name: str
     vendor_code: str
 
+    # Usage counts (for admin display)
+    products_count: int | None = None
+    team_count: int | None = None
+
 
 class VendorSubscriptionListResponse(BaseModel):
     """Response for listing vendor subscriptions."""
@@ -157,6 +161,15 @@ class VendorSubscriptionListResponse(BaseModel):
     pages: int
 
 
+class VendorSubscriptionCreate(BaseModel):
+    """Schema for admin creating a vendor subscription."""
+
+    tier: str = "essential"
+    status: str = "trial"
+    trial_days: int = 14
+    is_annual: bool = False
+
+
 class VendorSubscriptionUpdate(BaseModel):
     """Schema for admin updating a vendor subscription."""
 

models/schema/subscription.py

@@ -134,6 +134,22 @@ class SubscriptionUsage(BaseModel):
     team_members_percent_used: float | None
 
 
+class UsageSummary(BaseModel):
+    """Usage summary for billing page display."""
+
+    orders_this_period: int
+    orders_limit: int | None
+    orders_remaining: int | None
+
+    products_count: int
+    products_limit: int | None
+    products_remaining: int | None
+
+    team_count: int
+    team_limit: int | None
+    team_remaining: int | None
+
+
 class SubscriptionStatusResponse(BaseModel):
     """Subscription status with usage and limits."""
 

static/admin/js/vendor-detail.js

@@ -12,9 +12,11 @@ function adminVendorDetail() {
         // Vendor detail page specific state
         currentPage: 'vendor-detail',
         vendor: null,
+        subscription: null,
         loading: false,
         error: null,
         vendorCode: null,
+        showSubscriptionModal: false,
 
         // Initialize
         async init() {
@@ -35,6 +37,10 @@ function adminVendorDetail() {
                 this.vendorCode = match[1];
                 detailLog.info('Viewing vendor:', this.vendorCode);
                 await this.loadVendor();
+                // Load subscription after vendor is loaded
+                if (this.vendor?.id) {
+                    await this.loadSubscription();
+                }
             } else {
                 detailLog.error('No vendor code in URL');
                 this.error = 'Invalid vendor URL';
@@ -91,6 +97,82 @@ function adminVendorDetail() {
             return formatted;
         },
 
+        // Load subscription data for this vendor
+        async loadSubscription() {
+            if (!this.vendor?.id) {
+                detailLog.warn('Cannot load subscription: no vendor ID');
+                return;
+            }
+
+            detailLog.info('Loading subscription for vendor:', this.vendor.id);
+
+            try {
+                const url = `/admin/subscriptions/${this.vendor.id}`;
+                window.LogConfig.logApiCall('GET', url, null, 'request');
+
+                const response = await apiClient.get(url);
+                window.LogConfig.logApiCall('GET', url, response, 'response');
+
+                this.subscription = response;
+                detailLog.info('Subscription loaded:', {
+                    tier: this.subscription?.tier,
+                    status: this.subscription?.status,
+                    orders_this_period: this.subscription?.orders_this_period
+                });
+
+            } catch (error) {
+                // 404 means no subscription exists - that's OK
+                if (error.status === 404) {
+                    detailLog.info('No subscription found for vendor');
+                    this.subscription = null;
+                } else {
+                    detailLog.warn('Failed to load subscription:', error.message);
+                }
+            }
+        },
+
+        // Get usage bar color based on percentage
+        getUsageBarColor(current, limit) {
+            if (!limit || limit === 0) return 'bg-blue-500';
+            const percent = (current / limit) * 100;
+            if (percent >= 90) return 'bg-red-500';
+            if (percent >= 75) return 'bg-yellow-500';
+            return 'bg-green-500';
+        },
+
+        // Create a new subscription for this vendor
+        async createSubscription() {
+            if (!this.vendor?.id) {
+                Utils.showToast('No vendor loaded', 'error');
+                return;
+            }
+
+            detailLog.info('Creating subscription for vendor:', this.vendor.id);
+
+            try {
+                // Create a trial subscription with default tier
+                const url = `/admin/subscriptions/${this.vendor.id}`;
+                const data = {
+                    tier: 'essential',
+                    status: 'trial',
+                    trial_days: 14,
+                    is_annual: false
+                };
+
+                window.LogConfig.logApiCall('POST', url, data, 'request');
+                const response = await apiClient.post(url, data);
+                window.LogConfig.logApiCall('POST', url, response, 'response');
+
+                this.subscription = response;
+                Utils.showToast('Subscription created successfully', 'success');
+                detailLog.info('Subscription created:', this.subscription);
+
+            } catch (error) {
+                window.LogConfig.logError(error, 'Create Subscription');
+                Utils.showToast(error.message || 'Failed to create subscription', 'error');
+            }
+        },
+
         // Delete vendor
         async deleteVendor() {
             detailLog.info('Delete vendor requested:', this.vendorCode);

static/vendor/js/billing.js

@@ -17,7 +17,9 @@ function billingData() {
         showCancelModal: false,
         showSuccessMessage: false,
         showCancelMessage: false,
+        showAddonSuccessMessage: false,
         cancelReason: '',
+        purchasingAddon: null,
 
         // Initialize
         async init() {
@@ -25,13 +27,16 @@ function billingData() {
             const params = new URLSearchParams(window.location.search);
             if (params.get('success') === 'true') {
                 this.showSuccessMessage = true;
-                // Clean URL
                 window.history.replaceState({}, document.title, window.location.pathname);
             }
             if (params.get('cancelled') === 'true') {
                 this.showCancelMessage = true;
                 window.history.replaceState({}, document.title, window.location.pathname);
             }
+            if (params.get('addon_success') === 'true') {
+                this.showAddonSuccessMessage = true;
+                window.history.replaceState({}, document.title, window.location.pathname);
+            }
 
             await this.loadData();
         },
@@ -40,16 +45,18 @@ function billingData() {
             this.loading = true;
             try {
                 // Load all data in parallel
-                const [subscriptionRes, tiersRes, addonsRes, invoicesRes] = await Promise.all([
+                const [subscriptionRes, tiersRes, addonsRes, myAddonsRes, invoicesRes] = await Promise.all([
                     this.apiGet('/billing/subscription'),
                     this.apiGet('/billing/tiers'),
                     this.apiGet('/billing/addons'),
+                    this.apiGet('/billing/my-addons'),
                     this.apiGet('/billing/invoices?limit=5'),
                 ]);
 
                 this.subscription = subscriptionRes;
                 this.tiers = tiersRes.tiers || [];
                 this.addons = addonsRes || [];
+                this.myAddons = myAddonsRes || [];
                 this.invoices = invoicesRes.invoices || [];
 
             } catch (error) {
@@ -119,6 +126,45 @@ function billingData() {
             }
         },
 
+        async purchaseAddon(addon) {
+            this.purchasingAddon = addon.code;
+            try {
+                const response = await this.apiPost('/billing/addons/purchase', {
+                    addon_code: addon.code,
+                    quantity: 1
+                });
+
+                if (response.checkout_url) {
+                    window.location.href = response.checkout_url;
+                }
+            } catch (error) {
+                console.error('Error purchasing addon:', error);
+                this.showNotification('Failed to purchase add-on', 'error');
+            } finally {
+                this.purchasingAddon = null;
+            }
+        },
+
+        async cancelAddon(addon) {
+            if (!confirm(`Are you sure you want to cancel ${addon.addon_name}?`)) {
+                return;
+            }
+
+            try {
+                await this.apiDelete(`/billing/addons/${addon.id}`);
+                this.showNotification('Add-on cancelled successfully', 'success');
+                await this.loadData();
+            } catch (error) {
+                console.error('Error cancelling addon:', error);
+                this.showNotification('Failed to cancel add-on', 'error');
+            }
+        },
+
+        // Check if addon is already purchased
+        isAddonPurchased(addonCode) {
+            return this.myAddons.some(a => a.addon_code === addonCode && a.status === 'active');
+        },
+
         // API helpers
         async apiGet(endpoint) {
             const response = await fetch(`/api/v1/vendor${endpoint}`, {
@@ -153,6 +199,23 @@ function billingData() {
             return response.json();
         },
 
+        async apiDelete(endpoint) {
+            const response = await fetch(`/api/v1/vendor${endpoint}`, {
+                method: 'DELETE',
+                headers: {
+                    'Content-Type': 'application/json',
+                },
+                credentials: 'include'
+            });
+
+            if (!response.ok) {
+                const error = await response.json().catch(() => ({}));
+                throw new Error(error.detail || `API error: ${response.status}`);
+            }
+
+            return response.json();
+        },
+
         // Formatters
         formatDate(dateString) {
             if (!dateString) return '-';