Ultra-long behavior sequences (10K+ events) with real trade-offs between positional-encoding extrapolation, attention cost, and online latency and storage; decoupling stable preferences from seasonal demand, momentary impulses, and needs already satisfied; and mining implicit negative feedback - impressions without clicks, consecutive skips, fast swipes - at every stage of the funnel. Iterate the model architectures that carry the funnel: multi-task and multi-objective learning from click through conversion and GMV; multi-scenario, multi-format joint modelling; and the sample, label, and debiasing design that decides what the model actually learns.