Reachability checks for latent world-model planning
Teams adding a world model to a VLA should test whether latent rollouts are usable by the planner before trusting prediction loss. OneWM-VLA gives a practical build path: keep most of π0 frozen, compress each camera view and frame into one semantic latent token, then generate future latent tokens and action chunks with one flow-matching model. The reported gains are large enough to justify a small prototype, including 98.1% average success on LIBERO and 71.7% average real Piper-arm success under clean conditions.
The missing check is plannability. RC-aux shows why: short-horizon latent prediction can still create latent shortcuts where a goal looks close but cannot be reached within the action budget. A cheap evaluation is to add finite-budget reachability labels and temporal hard negatives to the world-model test suite, then compare action success against terminal latent distance on obstacle or long-horizon tasks. On Wall, RC-aux raises success from 50.4 ± 6.5 for the LeWM control to 83.6 ± 3.6, with planner ablations showing that the reachability-aware planner adds value beyond training alone.