Separated H from K
Turned an implicit evaluation choice into the central controlled variable.
LeWMRO · ICML 2026 Workshop on Decision-Making from Offline Datasets to Online Adaptation · Oral
When a useful world model looks broken.
A planner can optimize a future it never executes. And a latent state can look close to the goal without offering a controllable route there. We isolated both interface failures and showed what changes when the evaluation matches the controller.
Walk it · 3D protocol world
Stand inside the planning loop.
A staged world for both failure modes. Watch a fifteen-step plan grow and get thrown away three chunks at a time, then steer an agent through the detour that a scalar objective cannot see. Every number in its console is quoted from the paper. The motion is staged, not replayed.
Still image · click to load the world Open on its own page ↗
The thesis
A world-model benchmark does not measure the model alone. It measures a chain: representation → objective → proposal mechanism → actuator. A mismatch anywhere in that interface can turn a usable model into an apparent failure.
Failure 01 · objective-execution mismatch
The planner imagines fifteen steps. The controller takes three.
Receding-horizon MPC plans to horizon H, executes only K action chunks, observes the new state, and replans. Terminal@H scores a state the controller will not directly reach before feedback changes the plan.
Protocol explainer · not a live rerun
What exactly gets scored?
score ẑH
H = 15
nowimagined future
executed prefix
The objective rewards the imagined endpoint at H=15, although feedback arrives after K=3. The unexecuted suffix can dominate which prefix is selected.
Measured on PushT · H=15 · K=3
The same check changes TwoRoom from 52.0% to 83.5%; a running cost changes Reacher from 20.5% to 100%.
Measured control
Move the feedback boundary without changing the model.
Across the measured replanning intervals K ∈ {1, 3, 5, 15}, terminal scoring is fragile under partial execution while running cost stays strong with frequent feedback. The intermediate PushT values are not monotonic. The finding is alignment, not a smooth performance law.
Failure 02 · controllability mismatch
Closer in latent space does not always mean reachable.
TwoRoom Far Door forces the agent to move away from the final goal to reach a distant doorway. Even aligned scalar objectives remain weak because they reward similarity, not locally executable progress through the bottleneck.
Best scalar/value objective26.5%
Waypoint + nearest retrieval92.7%
Matched-configuration reproduction · held-out fold 0 · episode 04 / 12
Watch the interface change the first move.
H 15 planK 3 execute↻ replan
Best scalar/value formepisode failed
Nearest waypoint + local actuatorepisode succeeded
first post-step hit held
Matched-configuration reproduction on held-out fold 0. The agent starts left of the far doorway; the waypoint controller first redirects it through that opening. TwoRoom counts a hit when agent-goal distance is below 16; success is reach-once within the 75-step budget. The waypoint library and local actuator exclude that evaluation fold. The overlay is the solver's recorded selection, not an inferred path. The 92.7% headline is the paper's five-fold mean, not the outcome of this clip.
Actual dataset geometry
The useful first move is away from the goal.
The stored expert trajectories descend to the low far doorway, cross the wall, then climb toward the high goal. The waypoint interface turns that detour into a sequence of locally executable edges.
What I led
I led the experiments that separated the two failure modes.
Built diagnostic controls
Compared terminal, prefix-terminal, running-cost, value, retrieval, and waypoint interfaces.
Designed deceptive tasks
Created detour settings that distinguish latent similarity from controllable progress.
Made the claim narrower
Reported strong retrieval controls and reset-state artifacts instead of hiding inconvenient evidence.
What this does not claim
A diagnostic, not a universal planner.
- Running costs and receding-horizon MPC are established control machinery, not new inventions.
- Waypoint retrieval is a useful repair and control, not a final general planning algorithm.
- Nearest retrieval remains the strongest held-out waypoint selector in the main deceptive task.
- The PushT Gate reset-state artifact is treated as a sanity check, not headline evidence.