Process 05 — payment-saga happy path

Process 05 — payment-saga happy path

Successful flow: auction closes → top bidder’s saved card charges first try (no 3DS) → invoice issued → ad activates at T+24h.

Key invariants on the happy path

• instance_id is exactly auction_id throughout.
• Every Stripe call has Idempotency-Key: ${saga_instance_id}:${step}:${attempt} with attempt=1.
• The webhook bridge only signals; it does not write to D1.
• invoices.retrieve is called at the top of the post-event step to guard against the bridge having lost the payload.
• Total wall-clock on a fully successful run: dominated by step.sleepUntil(T+24h); CPU work is < 5s.