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Zero-shot World Models via Search in Memory
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Proposes zero-shot world models that approximate latent transition dynamics via similarity search over stored VAE latents (Rollout, Replay-L2, Replay-KL), without training a dynamics model, and compares them to PlaNet.
Problem
Learning-based world models need large data and compute to model environment dynamics; the paper asks whether next-state and long-horizon dynamics can be predicted without training a dynamics model.
Approach
Combine similarity search over a memory of encoded VAE latent transitions with the stochastic (Normal) latent representation to sample next latents, iterating retrieve-and-reconstruct for long horizons, with three memory structures (rollout buffer, replay buffer with L2 or KL-divergence retrieval).
Key results
- On SuperTuxKart planning, Replay-KL reaches 15.66 mean reward on snowmountain versus 5.32 for PlaNet, and replay-based methods win 4 of 5 tracks.
- Search-based Rollout and Replay-KL are visually comparable to PlaNet in one-step prediction and better in long-horizon prediction on SuperTuxKart; Replay-L2 hallucinates in reconstruction.
- Inference time for the search-based methods is about 0.0008 to 0.0025 s versus 0.044 s for PlaNet on SuperTuxKart.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use search-based world models instead of PlaNet for planning | SuperTuxKart · SuperTuxKart planning across five tracks | mean reward | Helped |
| Replace Rollout retrieval with Replay-L2 retrieval | Zero-shot world model · SuperTuxKart dynamics reconstruction | visual reconstruction | Hurt |
| Use Rollout or Replay-KL instead of PlaNet | World model · SuperTuxKart long-horizon prediction | reconstruction quality | Helped |
| Increase the number of encoded trajectories (ablation) | PlaNet SSM · SuperTuxKart tracks | KL divergence: 339.48 to 169.46; -26.56% | Helped |
| Increase the number of encoded trajectories (ablation) | Rollout · SuperTuxKart tracks | KL divergence: 311.89 to 86.27; -72.34% | Helped |
| Increase the number of encoded trajectories (ablation) | Replay-L2 and Replay-KL · SuperTuxKart tracks | prediction quality | No clear effect |
| Remove action conditioning (ablation) | Replay-L2 · Dynamics prediction | KL divergence | Helped |
| Remove action conditioning (ablation) | Rollout · One-step prediction | KL divergence | Helped |
| Remove action conditioning (ablation) | Rollout · Long-horizon prediction | KL divergence | No clear effect |
| Remove action conditioning (ablation) | Replay-KL · One-step prediction | KL divergence | No clear effect |
| Remove action conditioning (ablation) | Replay-KL · Long-horizon prediction | KL divergence | Helped |
| Use more encoded trajectories for retrieval (ablation) | Zero-shot world model · Minecraft Treechop-v0 | visual resemblance | Helped |
Surprising findings
- Replay-L2 achieves low latent KL error yet produces visually incoherent decoded images, showing latent-space metrics can mislead.
- Increasing the number of stored trajectories substantially improves the PlaNet baseline but only marginally helps the search-based models.
Limitations
- Performance depends on latent-space coverage of stored trajectories, so it struggles in open-ended tasks such as Minecraft Navigate.
- Requires access to future actions for prediction, so it is not directly usable for action selection without extra assumptions.
- Replay-L2 and some methods produce visually incoherent or hallucinated reconstructions; memory grows with stored data (about 12GB RAM).
Experimental setup
Datasets: SuperTuxKart MineRL Treechop-v0 MineRL Navigate-v0 Atari Seaquest Atari Space Invaders
Benchmarks: SuperTuxKart MineRL Treechop-v0 MineRL Navigate-v0 Atari Seaquest Atari Space Invaders
Metrics: KL divergence L1 distance SSIM mean reward inference time
Baselines: PlaNet
Builds on: PlaNet Dreamer locally weighted learning Zero-shot Imitation Policy beta-VAE
Closest papers by meaning
- Learning Visual Feature-Based World Models via Residual Latent Action (NeurIPS 2026 · similarity 0.90)
- DINO-WM: World Models on Pre-trained Visual Features enable Zero-shot Planning (ICML 2025 · similarity 0.89)
- Reinforcing VLAs in Task-Agnostic World Models (NeurIPS 2026 · similarity 0.89)
- RLVR-World: Training World Models with Reinforcement Learning (NeurIPS 2025 · similarity 0.89)
- Open-World Reinforcement Learning over Long Short-Term Imagination (ICLR 2025 · similarity 0.89)
- Learning Latent Dynamic Robust Representations for World Models (ICML 2024 · similarity 0.89)
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