Aim Short to Reach Far: Your Frozen World Model Can Plan Better Than You Think

Xvyuan Liu; Jianjie Fang; Wei Wu; Chen Gao; Yong Li

cs.LGSep 24, 2026

Aim Short to Reach Far: Your Frozen World Model Can Plan Better Than You Think

Authors: Xvyuan Liu, Jianjie Fang, Wei Wu, Chen Gao, Yong Li

Organizations: Tsinghua University

Abstract

Latent world models plan toward goal images with a frozen pretrained predictor, without task rewards or extra trained heads. However, their planners struggle with long-range goals, and prior work addresses this by training extra components such as value functions or subgoal models. We show that the planning target itself can cause this failure: even with exact dynamics and globally optimal short-horizon search, scoring predictions by their distance to the final goal rejects the first steps of a route that initially moves away from the goal. Building on this insight, we propose Anchored Planning (AP), a training-free method that reuses the world model's own offline trajectories. AP retrieves a segment that leads from the current observation toward the goal and aims the frozen planner at an observation shortly after the segment's start. Across four diverse tasks, AP substantially improves frozen LeWM planners for both action synthesis and action ranking, and it outperforms both additional final-goal search and the LeWM planner on long-range goals.

Figures & tables

Figure 1: Changing the target improves control with the same frozen predictor. (a) Both target rules score the same endpoints

p_{i}=F(z_{t},u_{i})

. Final-goal scoring selects

u_{1}

, whereas observed-target scoring selects

u_{2}

. Solid curves show predictions, and dashed segments show scoring distances. The target inset shows a recorded successor. Positions and observations are schematic. (b) On PushT, intermediate targets sustain control as the recorded goal offset grows. Curves use paired standard-start queries and the same frozen LeWM weights.

		No memory	Observation-only			Recorded actions
Task	Start	LeWM	CEM final	CEM learned	AP-CEM	Direct	Rank final	Rank learned	AP-rank
Cube	Standard	15.6	7.0	62.5	46.9	82.0	62.5	91.4	73.4
	Perturbed	12.5	2.7	38.7	29.7	47.7	41.8	50.0	45.7
PushT	Standard	7.0	2.3	52.3	69.5	51.6	25.8	54.7	66.4
	Perturbed	9.4	2.7	48.8	64.8	18.0	12.9	35.5	47.7
Reacher	Standard	66.4	25.8	54.7	75.8	99.2	90.6	95.3	96.9

Table 1: Intermediate targets improve control with the same frozen model. We report success (%) on 128 paired queries per task. Column groups indicate what experience each controller can use. Learned targets are trained on memory observations. For perturbed starts, we average within each query, and task means weight all tasks equally. Bold marks the highest success within each group of controllers. AP-CEM and AP-rank use observed targets.

	Successor error		CEM success (%)
Task	Learned	Observed	Learned	Observed
Cube	19.708	63.056	62.5	46.9
PushT	3.774	10.668	52.3	69.5
Reacher	74.724	154.351	54.7	75.8
TwoRoom	133.857	266.676	53.1	46.9

Table 2: Training-free observed targets achieve higher mean success than a more accurate learned target. We measure the mean squared distance to the recorded successor on held-out memory transitions and CEM success on standard-start evaluation queries. Bold marks higher success. Appendix C.1 explains how target accuracy is measured.

(a) Target offset and memory size
	AP-rank		AP-CEM
Variant	Standard	Perturbed	Standard	Perturbed
Target $\ell=1$	69.5	61.3	43.0	37.9
Target $\ell=3$	78.5	68.5	69.9	62.6
Target $\ell=5$ (default)	83.8	72.3	59.8	55.1
Target $\ell=10$	81.6	68.4	54.1	52.7

Table 3: Target placement and retrieval timing determine how memory guides control. We average success (%) across the four tasks. Predictions span

L=5

actions, and

\ell

sets the target’s offset in the recorded trajectory. When varying memory size, we keep the default target offset. In the fixed-span setting, we use

h=H

throughout execution. Bold marks the highest mean per column within each panel.

		Endpoint error		Selection regret
Task	Start	Predictor	Displ.	Predictor	Displ.	Direct
Cube	Standard	7.538	35.344	5.332	7.535	11.375
	Perturbed	37.726	66.860	8.472	11.731	14.903
PushT	Standard	1.532	3.078	0.200	0.580	0.849
	Perturbed	2.980	9.562	0.753	2.418	4.449
Reacher	Standard	25.243	51.917	8.644	15.058	18.640

Table 4: Live-state prediction improves endpoint accuracy and action selection. We report mean squared latent distances in task-specific units, with lower values indicating better performance. Bold marks each metric’s minimum. Displacement transfers recorded motion, whereas Direct executes the closest record’s action. We exclude starts if any candidate ends before five actions (at most 3 of 128 standard and 6 of 256 perturbed starts per task).

Appendix figures & tables14 assets

Supplementary material from the paper’s appendix.

Appendix

Task	Cube	PushT	Reacher	TwoRoom
$H$	150	140	150	100
$B$	150	280	300	200
Memory	8,000	16,688	8,000	8,000

Appendix

Table 5: Evaluation inputs.

H

is the recorded goal offset,

B

the primitive-action allowance, and memory the number of eligible episodes.

Task	Width	Output	Best step	Validation MSE
Cube	512	Absolute	48,500	0.104926
	512	Residual	48,500	0.104579
	1024	Absolute	41,000	0.104422
	1024	Residual	48,500	0.102646
PushT	512	Absolute	48,000	0.023950
	512	Residual	48,000	0.024007

Appendix

Table 6: Selecting learned targets on held-out memory. We average squared error over latent coordinates to compute validation MSE. Bold marks the selected configuration.

Task	Controller	Standard		Perturbed
		Stalling	Detour	Stalling	Detour
Cube	LeWM	39.8 (43/108)	10.5 (2/19)	48.2 (108/224)	6.7 (2/30)
	CEM (final goal)	100.0 (119/119)	37.5 (3/8)	100.0 (249/249)	40.0 (2/5)
	CEM (learned)	79.2 (38/48)	60.8 (48/79)	89.2 (140/157)	68.0 (66/97)
	AP-CEM	86.8 (59/68)	66.1 (39/59)	92.2 (166/180)	73.0 (54/74)
	CEM (transported)	91.3 (73/80)	68.1 (32/47)	95.4 (186/195)	71.2 (42/59)

Appendix

Table 7: Physical behavior at the original goal offsets. Each percentage is followed by the number of positive cases and eligible rollouts. With

W=10

, we measure stalling over failed rollouts in which the policy made at least one decision. With

\delta=0.5

, we measure detours over successful rollouts that entered policy control. For perturbed behavior, we pool eligible rollouts from both prefixes.

Controller	Start	Stalling window			Detour threshold
		$W=5$	$10$	$20$	$\delta=0.25$	$0.5$	$1.0$
CEM (final goal)	Standard	55.1	53.3	49.9	68.6	30.6	29.1
CEM (final goal)	Perturbed	54.9	52.7	49.7	46.4	32.5	19.0
CEM (learned)	Standard	46.1	39.9	31.4	77.6	70.0	53.7
CEM (learned)	Perturbed	45.6	42.7	32.1	79.3	72.0	58.9
AP-CEM	Standard	51.7	49.5	40.5	90.6	84.1	70.7

Appendix

Table 8: Behavior across thresholds. We average rates (%) equally across the four tasks, computing each rate from that task’s eligible rollout counts.

Task	Iterations	Final goal		Learned target		Observed target
		Standard	Perturbed	Standard	Perturbed	Standard	Perturbed
Cube	1	3.9	2.0	11.7	6.6	10.9	7.0
	2	3.1	2.3	40.6	26.2	26.6	15.6
	5	3.1	2.3	52.3	34.0	36.7	26.6
	10	4.7	3.9	59.4	35.2	44.5	29.7
	30	7.0	2.7	62.5	38.7	46.9	29.7

Appendix

Table 9: Success across search budgets. We report success (%) on the main queries at the original offsets. Only the number of CEM iterations changes, and each decision evaluates

300I+2

predicted blocks. For perturbed starts, we average the two starts of each query.

Task	Paper report	LeWM evaluator	Our implementation
Cube	74.0	74.7	74.7
PushT	96.0	92.0	91.3
Reacher	86.0	80.0	80.0
TwoRoom	87.0	87.3	87.3

Appendix

Table 10: LeWM under its evaluation protocol. We compare published success (%) from Figure 6 of Maes et al. [2026] with measurements from the LeWM evaluator and our implementation on the same queries. Measurements are averaged over three seeds with 50 queries each, including the seed specified in the LeWM configuration.

	Success (%)		Work ( $10^{3}$ blocks)
Task	Standard	Perturbed	Standard	Perturbed
Cube	13.3	13.3	1,189	1,197
PushT	7.0	8.2	2,402	2,374
Reacher	73.4	77.3	1,388	1,322
TwoRoom	27.3	25.8	1,500	1,509

Appendix

Table 11: LeWM with five-action replanning. The variant keeps the 25-action lookahead and the LeWM CEM settings and changes only execution, which now covers one five-action block. Evaluation uses the main queries and original goal offsets, with 128 standard starts and 256 perturbed starts per task. Work is the mean number of predicted five-action blocks per episode, in thousands as in Table 13 .

Task	$H$	LeWM		Final goal		Learned		AP-CEM
		Std.	Pert.	Std.	Pert.	Std.	Pert.	Std.	Pert.
Cube	25	32.0	33.6	28.9	26.2	75.0	53.9	63.3	49.6
	50	16.4	12.1	7.0	4.3	58.6	37.9	47.7	30.5
	100	18.8	13.3	8.6	9.0	55.5	34.8	32.0	25.4
	150	15.6	12.5	7.0	2.7	62.5	38.7	46.9	29.7
PushT	25	60.9	57.8	51.6	46.9	91.4	75.4	91.4	87.5

Appendix

Table 12: Success across recorded goal offsets. To compare success (%) across offsets, we keep query sources fixed and move the goal to the observation

H

actions later, preserving each task’s

B/H

. Prediction lookahead and target-model training remain unchanged. Results are shown for standard starts (Std.) and for the average of each query’s perturbed starts (Pert.).

Controller	Cube		PushT		Reacher		TwoRoom
	Std.	Pert.	Std.	Pert.	Std.	Pert.	Std.	Pert.
LeWM	235.20	241.88	514.69	505.37	255.59	244.51	320.98	321.50
CEM (final goal)	252.62	263.17	493.56	491.10	407.76	425.31	354.95	354.95
CEM (learned)	142.27	191.54	375.06	387.40	393.91	379.98	250.65	247.94
AP-CEM	170.26	206.84	326.11	338.63	323.58	313.17	262.61	265.07
CEM (transported)	193.40	223.26	347.84	393.80	306.56	310.50	289.19	291.37

Appendix

Table 13: Mean episode prediction work at the original offsets. Values are thousands of predicted five-action blocks per episode. Columns marked Std. show standard starts, and those marked Pert. show the average of each query’s perturbed starts.

AP-CEM
Setting	Cube		PushT		Reacher		TwoRoom
	Std.	Pert.	Std.	Pert.	Std.	Pert.	Std.	Pert.
Default	46.9	29.7	69.5	64.8	75.8	78.9	46.9	46.9
$\ell=1$	43.8	31.3	34.4	29.3	50.0	44.9	43.8	46.1
$\ell=3$	61.7	42.6	68.8	60.9	91.4	90.6	57.8	56.3
$\ell=10$	19.5	15.6	58.6	57.4	87.5	89.8	50.8	48.0

Appendix

Table 14: Target offsets and memory size. On the main queries, we measure success (%) while varying the target offset or memory size. By default, the target is the five-step successor and retrieval uses the full memory. Prediction and execution retain five-action blocks throughout.

Setting	Cube		PushT		Reacher		TwoRoom
	Std.	Pert.	Std.	Pert.	Std.	Pert.	Std.	Pert.
Full key	73.4	45.7	66.4	47.7	96.9	95.7	98.4	100.0
Without distant endpoint	81.3	46.5	67.2	50.4	94.5	94.5	100.0	100.0
Without displacement	73.4	45.7	63.3	44.9	96.1	97.7	99.2	100.0
Fixed span $h=H$	4.7	3.1	0.0	0.0	12.5	19.1	21.1	23.0

Appendix

Table 15: Retrieval keys and temporal span. For AP-rank, we compare success (%) on the main queries. When omitting a key component, we keep the other components unchanged. Fixing

h=H

replaces the adaptive span

\max(5,H-t)

Task	Start	Observed target	Transported target
Cube	Standard	46.9	37.5
	Perturbed	29.7	23.8
PushT	Standard	69.5	61.7
	Perturbed	64.8	44.5
Reacher	Standard	75.8	81.3
	Perturbed	78.9	80.5

Appendix

Table 16: Anchoring and displacement transport on the main queries. Under the same CEM search, we compare success (%) when using the observed endpoint or transported motion. At perturbed starts, we average the two starts of each query, and the mean weights all tasks equally.

First-block selector	Cube		PushT		Reacher		TwoRoom
	Std.	Pert.	Std.	Pert.	Std.	Pert.	Std.	Pert.
Direct	82.0	47.7	51.6	18.0	99.2	96.9	99.2	100.0
Predictor / Final	67.2	43.0	39.1	18.4	96.1	97.3	100.0	100.0
Simulator / Final	73.4	44.5	43.0	19.1	96.1	97.3	99.2	99.6
Predictor / Learned	85.9	48.8	45.3	18.8	96.9	97.7	100.0	99.6
Simulator / Learned	86.7	49.2	42.2	22.3	96.9	97.7	100.0	99.6

Appendix

Table 17: Changing only the first action block. After selecting the first block, we use the same Direct continuation to measure success (%). Predictor and simulator selectors score the same eight candidates against the indicated target. All 128 assigned queries per task are included.

Task	CEM: Standard		Ranking: Standard		Ranking: Perturbed
	Final	Observed	Final	Observed	Final	Observed
Cube	8.6	39.1	64.8	71.1	41.4	43.4
PushT	1.6	81.3	25.8	78.1	9.0	49.2
Reacher	25.0	75.8	92.2	95.3	88.7	95.7
TwoRoom	0.8	39.1	85.2	100.0	88.3	99.6

Appendix

Table 18: Target effects on independent supporting queries. For each action rule, we compare success (%) with final-goal and observed targets. Ranking is evaluated at standard and perturbed starts, whereas CEM is evaluated at standard starts. Within each query, we average the two assigned perturbed starts.

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