Billing

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Two additional billing operations live outside billingActions but use the same evaluate+execute pipeline:

• createAllocatedInvoice — mid-cycle invoicing triggered by balance deduction
• createCustomerWithDefaults — customer creation with default products

Action Quick Reference

Each HTTP action also has a preview variant (billing.preview_attach, billing.preview_multi_attach, billing.preview_update) that runs setup+compute+evaluate but skips execution.

The legacy V1 attach (POST /attach) still exists and delegates to billingActions.legacy.attach, which converts old AttachParams format into V2 billing context overrides. Similarly legacyUpdateQuantity and legacyRenew bridge old flows to V2.

Handler Pattern

Handlers are thin wrappers — they parse params, call the action, format response:

// billing/v2/handlers/handleAttachV2.ts
export const handleAttachV2 = createRoute({
  versionedBody: { latest: AttachParamsV1Schema, [ApiVersion.V1_Beta]: AttachParamsV0Schema },
  resource: AffectedResource.Attach,
  lock: { /* distributed lock per customer */ },
  handler: async (c) => {
    const ctx = c.get("ctx");
    const body = c.req.valid("json");

    const { billingContext, billingResult } = await billingActions.attach({
      ctx,
      params: body,
      preview: false,
    });

    return c.json(billingResultToResponse({ billingContext, billingResult }), 200);
  },
});

The 4-Layer Pattern (Inside Each Action)

Every action follows: Setup → Compute → Evaluate → Execute

// billing/v2/actions/attach/attach.ts (simplified)
export async function attach({ ctx, params, preview }) {
  // 1. SETUP — Fetch all context (customer, Stripe, products, trial, cycle anchors)
  const billingContext = await setupAttachBillingContext({ ctx, params });

  // 2. COMPUTE — Determine Autumn state changes (new products, transitions, line items)
  const autumnBillingPlan = computeAttachPlan({ ctx, attachBillingContext: billingContext, params });

  // 3. EVALUATE — Map Autumn changes → Stripe actions (UNIFIED across all actions)
  const stripeBillingPlan = await evaluateStripeBillingPlan({ ctx, billingContext, autumnBillingPlan });

  // 4. ERRORS — Validate before execution
  handleAttachV2Errors({ ctx, billingContext, billingPlan, params });

  if (preview) return { billingContext, billingPlan };

  // 5. EXECUTE — Run Stripe first, then Autumn DB (UNIFIED across all actions)
  const billingResult = await executeBillingPlan({ ctx, billingContext, billingPlan });
  return { billingContext, billingPlan, billingResult };
}

Key principle: evaluateStripeBillingPlan and executeBillingPlan are UNIFIED across all actions. Only modify them when adding new Stripe action types.

See V2 Four-Layer Pattern Deep Dive for detailed explanation.

Allocated Invoice

Not an HTTP endpoint — triggered during executePostgresDeduction when allocated (prepaid) usage changes.

File: server/src/internal/balances/utils/allocatedInvoice/createAllocatedInvoice.ts

When it fires: A customer with usage-based allocated pricing (e.g., prepaid seats) has their usage change. The system needs to invoice for the delta.

Flow:

1. Setup (setupAllocatedInvoiceContext) — re-fetches full customer, computes previous/new usage and overage from entitlement snapshots
2. Compute (computeAllocatedInvoicePlan) — builds refund line item for previous usage + charge line item for new usage. Handles upgrade (delete replaceables) and downgrade (create replaceables) scenarios
3. Evaluate + Execute — standard unified pipeline (evaluateStripeBillingPlan → executeBillingPlan)
4. Post-execute — if Stripe invoice payment fails, voids invoice and throws PayInvoiceFailed
5. Mutation — calls refreshDeductionUpdate to mutate the deduction update with replaceable and balance changes

Key difference from other actions: Produces only updateCustomerEntitlements + lineItems (no insertCustomerProducts). The AutumnBillingPlan is minimal since the customer product already exists.

Two Critical Stripe Mappings

Getting billing right means getting these two mappings right:

1. Subscription Items (Immediate Changes)

When: Updating a subscription right now (add/remove/change items immediately)

Key function: buildStripeSubscriptionItemsUpdate

Flow:

FullCusProduct[] 
  → filter by subscription ID
  → filter by active statuses  
  → customerProductToStripeItemSpecs() 
  → diff against current subscription
  → Stripe.SubscriptionUpdateParams.Item[]

See Stripe Subscription Items Reference for details.

2. Schedule Phases (Future Changes)

When: Scheduling changes for the future (downgrades at cycle end, scheduled cancellations)

Key function: buildStripePhasesUpdate

Flow:

FullCusProduct[]
  → normalize timestamps to seconds
  → buildTransitionPoints() (find all start/end times)
  → for each period: filter active products
  → customerProductsToPhaseItems()
  → Stripe.SubscriptionScheduleUpdateParams.Phase[]

See Stripe Schedule Phases Reference for details.

Stripe Invoice Decision Tree

Critical: Stripe sometimes forces invoice creation. If you also create a manual invoice, customer gets double-charged.

Does Stripe force-create an invoice?
├── Creating a new subscription? 
│   └── YES → Stripe creates invoice. DO NOT create manual invoice.
│
├── Removing trial from subscription? (isTrialing && !willBeTrialing)
│   └── YES → Stripe creates invoice. DO NOT create manual invoice.
│
└── Otherwise
    └── NO → We create manual invoice using buildStripeInvoiceAction()

Key functions:

• shouldCreateManualStripeInvoice() - Returns true if WE should create invoice
• willStripeSubscriptionUpdateCreateInvoice() - Returns true if STRIPE will create invoice

See Stripe Invoice Rules Reference for full decision tree.

Common Issues & Fixes

See Common Bugs Reference for detailed debugging steps.

Adding a New Billing Action

1. Create action function: billing/v2/actions/myAction/myAction.ts

   • Follow the attach.ts pattern: setup → compute → evaluate → errors → execute
   • Return { billingContext, billingPlan, billingResult }

2. Create setup function: billing/v2/actions/myAction/setup/setupMyActionBillingContext.ts

   • Extend BillingContext interface if needed
   • Use shared setup functions (setupFullCustomerContext, setupStripeBillingContext, etc.)

3. Create compute function: billing/v2/actions/myAction/compute/computeMyActionPlan.ts

   • Return AutumnBillingPlan with insertCustomerProducts, lineItems, etc.

4. Create error handler: billing/v2/actions/myAction/errors/handleMyActionErrors.ts

5. Register in billingActions: billing/v2/actions/index.ts

6. Create handler (if HTTP-exposed): billing/v2/handlers/handleMyAction.ts

   • Thin wrapper calling billingActions.myAction()

7. DO NOT modify evaluateStripeBillingPlan or executeBillingPlan unless absolutely necessary

Invoicing Utilities (Pure Calculations)

The shared/utils/billingUtils/ folder contains pure calculation functions that determine what customers are charged.

Key utilities:

Key concepts:

• LineItem.amount is positive for charges, negative for refunds
• context.direction controls the sign ("charge" vs "refund")
• Proration is applied automatically when billingPeriod is provided
• Consumable prices don't prorate (usage is charged as-is)

See Invoicing Utilities Reference for detailed documentation.

Key File Locations

V2 Actions (server/src/internal/billing/v2/actions/)

Shared V2 Infrastructure (server/src/internal/billing/v2/)

Non-billingActions Operations

Types

Reference Files

Load these on-demand for detailed information:

• V2 Four-Layer Pattern - Deep dive on each layer
• Stripe Subscription Items - Immediate changes mapping
• Stripe Schedule Phases - Future changes mapping
• Stripe Invoice Rules - Invoice decision tree
• Invoicing Utilities - Pure calculation functions for charges
• Common Bugs - Debugging guide with solutions