Session: stripe-webhook-idempotency — 2026-09-01

Project: ledger-api · Branch: feat/stripe-webhooks · Mode: default · Model: gpt-5-codex

Summary

Made Stripe webhook handling idempotent: every event id is recorded in a processed_events table inside the same transaction as the side effect, so retries from Stripe can never double-credit an invoice.

Conversation

Turn 1 — User

Stripe retries webhooks. Make sure we never apply the same event twice.

Turn 1 — Assistant

Insert the event id into processed_events (unique) in the same transaction as the invoice update; on a unique-violation, return 200 and skip. Signature verification stays first.

@router.post("/webhooks/stripe")
async def stripe_webhook(request: Request, db: Session = Depends(get_db)):
    event = verify_signature(await request.body(), request.headers)
    try:
        with db.begin():
            db.add(ProcessedEvent(id=event.id))
            apply_event(db, event)
    except IntegrityError:
        return {"status": "duplicate"}   # already handled
    return {"status": "ok"}

Tools used in this turn:

• Edit: ledger/webhooks.py
• Write: migrations/versions/0004_processed_events.py
• Bash: pytest tests/test_webhooks.py -q — 6 passed

Connections

• [[ledger-api]]
• [[Stripe]]
• [[Idempotency]]
• [[PostgreSQL]]