## Linear ticket
https://linear.app/chatwoot/issue/CW-6834/billing-upgrade-didnt-work
## Description
A `customer.subscription.updated` Stripe webhook for account 76162
returned 200 OK but did not persist the new `subscribed_quantity`. Root
cause: a race condition between the webhook handler and
`increment_response_usage` (Captain usage counter), both doing
read-modify-write on the `custom_attributes` JSONB column. The webhook
wrote `quantity: 6`, then a concurrent `save` from
`increment_response_usage` overwrote the entire hash with stale data —
restoring `quantity: 5`.
Fix: use atomic `jsonb_set` so usage counter updates only touch the
single key they care about, instead of rewriting the whole
`custom_attributes` hash. `increment_custom_attribute` also performs the
increment in SQL, making concurrent increments correct as well.
## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
## How Has This Been Tested?
- New regression spec in `handle_stripe_event_service_spec.rb` that
simulates concurrent webhook + `increment_response_usage` and asserts
both `subscribed_quantity` and `captain_responses_usage` survive
- Existing account, billing, captain, and topup specs all pass locally
## Checklist:
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules
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