Planning with world models enables test-time adaptation for embodied agents, offering superior generalization over direct policy learning. However, long-horizon tasks remain hindered by cumulative errors and search complexity. Existing hierarchical methods often use rigid macro-actions or latent skills, leading to brittle representations and limited fine-grained control. We introduce ID-WM (Implicit Dynamics World Models), a hierarchical world model that decouples state-space reachability from local control. Our framework utilizes a high-level model to sample feasible transitions across the state manifold and a low-level world model as an inverse dynamics solver to ground these transitions into precise actions. This allows the planner to identify reachable subgoals without being constrained by low-level execution details. By prioritizing local physical feasibility over global behavioral patterns, ID-WM synthesizes novel long-horizon plans from short segments, transcending the specific behavioral modes seen during training. We demonstrate its effectiveness across three navigation and manipulation suites, achieving a 38.5% improvement over state-of-the-art policy and diffusion-based planners. Crucially, by leveraging this hierarchical structure to mitigate compounding errors, our approach yields a 135% performance gain over single-level world model MPC, particularly in complex, unseen configurations for long-horizon tasks. Videos can be viewed at https://id-wm.github.io
Figures & tables
Figure 1: Overview of ID-WM . Our hierarchical planning framework decouples state-space reachability from local control, eliminating the reliance on task-specific value functions or pre-trained policies. Planning proceeds in two interleaved stages: (1) high-level planning, which discovers a sequence of temporally abstract subgoals spaced Δ steps apart, and (2) low-level control, which leverages a world model as an inverse dynamics solver to extract executable actions between each subgoal.
Figure 2: Architecture of ID-WM . Given an initial observation o0 and a goal og , we optimize for both the sequence of subgoals s0,…,sTΔ and the executable actions at in an interleaved fashion. Here, fhi denotes the diffusion-based high-level world model and flo denotes the deterministic, transformer-based low-level world model, both of which predict in latent space.
Figure 3: We evaluate ID-WM on three environment suites (Wall, PushT, Maze); from left to right: Wall, PushT, and the four maze sizes (U-, Medium, Large, Giant).
Figure 4: Diverse neighboring states generated with the high-level WM of ID-WM .
Figure 5: High-level subgoals planned by ID-WM . The planned sequence successfully guides the agent to the target goal while ensuring that consecutive subgoals satisfy local reachability constraints.
PushT
PushT-Aug
Method
Fix
Rand.
Fix
Rand.
HWM
0.38
0.20
0.42
0.16
ID-WM
1.00
0.77
1.00
1.00
Table 2: Success rate of ID-WM and HWM on PushT environments with fixed (Fix) and random (Rand.) goals.
Figure 6: Diverse plans generated by ID-WM . The top and bottom rows illustrate distinct strategies: counterclockwise and clockwise rotations of the T-block, both resulting in successful task completion.
Figure 7: Planning performance with increasing task complexity. In a), we test ID-WM ’s ability on Maze with increasing sizes. In b), we test ID-WM on increasingly longer horizon PushT tasks.
Figure 8: Subgoals generated by ID-WM on a visual PushT task. The first column denotes the starting state, and the last shaded column denotes the desired goal state. ID-WM generates reliable, sequential subgoals that drive steady progress toward the goal state without any degenerate states.
Method
d=25
d=50
d=75
Random Goal
DINO-WM
0.84
0.16
0.00
0.00
HWM
0.96
0.46
0.14
0.02
ID-WM
0.90
0.60
0.50
0.26
Table 3: Success rate on vision-based PushT. For d∈{25,50,75} the goal is d steps away; Random Goal samples both the initial and goal states randomly.
Figure 9: Examples of sampled initial and goal state pairs for the Wall, PushT, Giant Maze, Large Maze, and U-Maze environments
Figure 10: Success rate with respect to CEM samples and noise regularization.
Δ \ #Subgoals
3
4
5
6
8
12
25
1
0.06
0.04
0.06
0.08
0.04
0.10
0.06
2
0.14
0.14
0.28
0.50
0.64
0.48
0.24
3
0.50
0.56
0.64
0.82
0.76
0.74
0.42
4
0.60
0.76
0.86
0.86
1.00
0.90
0.44
5
0.74
0.84
0.96
0.98
0.94
0.76
0.38
Table 4: Success rate on PushT-Aug (Random Goal) when sweeping the subgoal horizon Δ (rows) and the number of subgoals per high-level plan (columns). The default configuration ( Δ=5 , 5 subgoals) is underlined.
Method
PushT-Aug (Rand.)
Medium Maze
HIQL
307.4
34.1
GCBC
1014.9
336.8
Diffuser
N/A
287.8
H-Diffuser
713.9
169.4
SL-WM
312.5
229.5
ID-WM
234.7
163.9
Table 5: Average steps to success over successful trajectories (lower is better). N/A indicates that no trajectory succeeded.
Table 15
Method
Samples
Elites
Replans
Horizon
SR
SL-WM (CEM budget matched)
300
30
15
25
0.21
SL-WM (inference time matched)
300
30
45
25
0.28
ID-WM
300
30
15
5 (each level)
0.77
Table 8: Success rate on PushT (Random Goal) when matching either the CEM budget or the wall-clock inference time of SL-WM to ID-WM .
Table 17Table 18Table 19
Name
Value
lr
3e−4
Discount factor γ
0.99
Expectile τ
0.7
High-level α
3.0
Low-level α
3.0
Subgoal steps ksub
25
Table 15: Shared hyperparameters for HIQL across all evaluation environments.
Table 21
Model
Execution
PushT
PushT-Aug
Fix Goal
Random Goal
Fix Goal
Random Goal
SR
Cov
SR
Cov
SR
Cov
SR
Cov
Diffuser
execute plan + replan
0.00
0.03
0.00
0.03
0.28
0.37
0.06
0.19
Diffuser
execute one action + replan
0.00
0.11
0.00
0.06
0.04
0.27
0.02
0.15
Diffuser
execute plan
0.00
0.05
0.00
0.03
0.00
0.09
0.00
0.13
Table 18: Diffuser results across execution settings and PushT variants.
Model
Execution
PushT
PushT-Aug
Fix Goal
Random Goal
Fix Goal
Random Goal
SR
Cov
SR
Cov
SR
Cov
SR
Cov
H-Diffuser
execute plan + replan
0.38
0.28
0.00
0.08
0.56
0.51
0.46
0.36
H-Diffuser
execute one action + replan
0.00
0.25
0.02
0.11
0.56
0.56
0.26
0.50
H-Diffuser
execute plan
0.04
0.09
0.00
0.06
0.02
0.17
0.00
0.10
Table 19: H-Diffuser results across execution settings and PushT variants.
Figure 11: Training-time convergence of predicted future-state distributions for the PushT environment
Figure 12: Visualization of the induced state mappings by ID-WM and naive WM.
State Key Lab of General Artificial Intelligence, School of Intelligence Science and Technology, Peking University · Amazon AGI SF Lab · Institute for Artificial Intelligence, Peking University