The name does not define the interface
World-model architectures differ in what they observe, predict, and expose to a policy. Some condition on measured actions. Others learn from passive sequences and provide no direct control surface.
World action model is an emerging label. The useful technical question is whether actions condition the future, are predicted jointly, or serve as policy outputs.
Action trajectories are the data layer
A trajectory connects observation history, control input, state transition, and outcome without assuming one model architecture. It can support controllable video, behavior cloning, offline reinforcement learning, and learned simulation.
Each application still needs a specific action ontology, temporal resolution, environment coverage, and evaluation split.
Avoid category theater
Renaming passive clips as action data does not make a model controllable. Measured, inferred, generated, and unavailable actions must remain distinct.
Evaluate intervention sensitivity: change the action while holding context fixed, then measure whether the predicted future changes in a plausible and timely way.