REPLAY.

8 HAR-driven session replays inspected for regression. 3 replays trigger 4xx errors not present in the original capture. 1 replay surfaces a backend race condition only visible under timing.

A bug you can't replay is a bug you'll see in production again.

HF-005 · checkout-replay-031 RACE BUG

Race between cart-update and price-quote. Only visible at <80ms.

Add idempotency key, lock pricing on cart freeze, retest.