Second visualization from Wójtowicz's talk. Models each concurrent worker/stream as a vertical timeline and draws the actions happening on each. Demonstrated with an event-sourced shopping cart enforcing 'max 3 items' and a 'free gift on adding 2 items' policy: when the gift reaction runs inside the same transactional handler, the timeline is linear; when it runs on a separate stream/worker, the timeline forks. The visualization does not claim a race condition exists — it tells you you must analyze for one, because tests alone won't surface the possibility.