IPT is a 7-model sequential pipeline (soon 8 with Tracklet2ID) where changing any upstream model forces retraining multiple downstream models. The coupling is real: 64/71 SUSHI node features are raw ReID embeddings, track classification parses JND output positionally at [:3], [3:33], [33:].
The root cause is structural: models were added incrementally as independent units rather than designed as a coherent system.