Align Stripe plan changes to first-of-month proration anchors

src/Exceptionless.Web/Api/Handlers/OrganizationHandler.cs

@@ -438,7 +438,9 @@ public async Task<Result<ChangePlanResult>> Handle(ChangeOrganizationPlan messag
                 var subscriptionOptions = new SubscriptionCreateOptions
                 {
                     Customer = customer.Id,
-                    Items = [new SubscriptionItemOptions { Price = model.PlanId }]
+                    Items = [new SubscriptionItemOptions { Price = model.PlanId }],
+                    BillingCycleAnchorConfig = CreateMonthlyBillingCycleAnchorConfig(),
+                    ProrationBehavior = "create_prorations"
                 };
 
                 if (isPaymentMethod)
@@ -454,8 +456,18 @@ public async Task<Result<ChangePlanResult>> Handle(ChangeOrganizationPlan messag
             }
             else
             {
-                var update = new SubscriptionUpdateOptions { Items = [] };
-                var create = new SubscriptionCreateOptions { Customer = organization.StripeCustomerId, Items = [] };
+                var update = new SubscriptionUpdateOptions
+                {
+                    Items = [],
+                    ProrationBehavior = "create_prorations"
+                };
+                var create = new SubscriptionCreateOptions
+                {
+                    Customer = organization.StripeCustomerId,
+                    Items = [],
+                    BillingCycleAnchorConfig = CreateMonthlyBillingCycleAnchorConfig(),
+                    ProrationBehavior = "create_prorations"
+                };
                 bool cardUpdated = false;
 
                 var customerUpdateOptions = new CustomerUpdateOptions { Description = organization.Name };
@@ -543,6 +555,17 @@ await Task.WhenAll(
         return new ChangePlanResult { Success = true };
     }
 
+    private static SubscriptionBillingCycleAnchorConfigOptions CreateMonthlyBillingCycleAnchorConfig()
+    {
+        return new SubscriptionBillingCycleAnchorConfigOptions
+        {
+            DayOfMonth = 1,
+            Hour = 0,
+            Minute = 0,
+            Second = 0
+        };
+    }
+
     public async Task<Result<User>> Handle(AddOrganizationUser message)
     {
         if (String.IsNullOrEmpty(message.Id) || !message.Context.Request.CanAccessOrganization(message.Id) || String.IsNullOrEmpty(message.Email))

tests/Exceptionless.Tests/Api/Endpoints/OrganizationEndpointTests.cs

@@ -1391,6 +1391,12 @@ public async Task ChangePlanAsync_NewCustomerCreatesStripeCustomerAndSubscriptio
         var item = Assert.Single(subscription.Items);
         Assert.Equal(_plans.SmallPlan.Id, item.Price);
         Assert.Equal("coupon_10", Assert.Single(subscription.Discounts).Coupon);
+        Assert.Equal("create_prorations", subscription.ProrationBehavior);
+        Assert.NotNull(subscription.BillingCycleAnchorConfig);
+        Assert.Equal(1, subscription.BillingCycleAnchorConfig.DayOfMonth);
+        Assert.Equal(0, subscription.BillingCycleAnchorConfig.Hour);
+        Assert.Equal(0, subscription.BillingCycleAnchorConfig.Minute);
+        Assert.Equal(0, subscription.BillingCycleAnchorConfig.Second);
 
         var organization = await _organizationRepository.GetByIdAsync(SampleDataService.FREE_ORG_ID);
         Assert.NotNull(organization);
@@ -1444,6 +1450,7 @@ public async Task ChangePlanAsync_ExistingCustomerUpdatesPaymentMethodAndSubscri
         Assert.Equal("si_active", item.Id);
         Assert.Equal(_plans.SmallPlan.Id, item.Price);
         Assert.Equal("coupon_10", Assert.Single(updatedSubscription.Options.Discounts).Coupon);
+        Assert.Equal("create_prorations", updatedSubscription.Options.ProrationBehavior);
         Assert.Empty(StripeBillingClient.CreatedSubscriptionOptions);
 
         var organization = await _organizationRepository.GetByIdAsync(SampleDataService.FREE_ORG_ID);
@@ -1454,6 +1461,40 @@ public async Task ChangePlanAsync_ExistingCustomerUpdatesPaymentMethodAndSubscri
         Assert.Equal(BillingStatus.Active, organization.BillingStatus);
     }
 
+    [Fact]
+    public async Task ChangePlanAsync_ExistingCustomerWithoutSubscriptionCreatesMonthAlignedSubscription()
+    {
+        await SetStripeCustomerIdAsync(SampleDataService.FREE_ORG_ID, "cus_existing");
+
+        var result = await WithBillingEnabledAsync(() =>
+            SendRequestAsAsync<ChangePlanResult>(r => r
+                .AsFreeOrganizationUser()
+                .Post()
+                .AppendPaths("organizations", SampleDataService.FREE_ORG_ID, "change-plan")
+                .Content(new ChangePlanRequest
+                {
+                    PlanId = _plans.SmallPlan.Id,
+                    StripeToken = "pm_card_visa",
+                    Last4 = "4242"
+                })
+                .StatusCodeShouldBeOk()
+            ));
+
+        Assert.NotNull(result);
+        Assert.True(result.Success, result.Message);
+
+        var subscription = Assert.Single(StripeBillingClient.CreatedSubscriptionOptions);
+        Assert.Equal("cus_existing", subscription.Customer);
+        Assert.Equal(_plans.SmallPlan.Id, Assert.Single(subscription.Items).Price);
+        Assert.Equal("create_prorations", subscription.ProrationBehavior);
+        Assert.NotNull(subscription.BillingCycleAnchorConfig);
+        Assert.Equal(1, subscription.BillingCycleAnchorConfig.DayOfMonth);
+        Assert.Equal(0, subscription.BillingCycleAnchorConfig.Hour);
+        Assert.Equal(0, subscription.BillingCycleAnchorConfig.Minute);
+        Assert.Equal(0, subscription.BillingCycleAnchorConfig.Second);
+        Assert.Empty(StripeBillingClient.UpdatedSubscriptions);
+    }
+
     [Fact]
     public async Task ChangePlanAsync_FreePlanCancelsActiveStripeSubscriptions()
     {