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Mixture-of-Experts Meets In-Context Reinforcement Learning
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Proposes T2MIR, which replaces transformer feedforward layers with parallel token-wise and task-wise mixture-of-experts layers (the task router trained with an InfoNCE contrastive loss) to improve in-context RL on AD and DPT backbones.
Problem
In-context RL struggles with the multi-modal state-action-reward token data and with gradient conflicts across a diverse, heterogeneous task distribution within a single transformer policy.
Approach
Substitute the transformer feedforward layer with two parallel MoE layers: a token-wise MoE routing each token by modality/semantics, and a task-wise MoE whose router is trained with a contrastive (InfoNCE, MoCo-style momentum) objective to maximize mutual information between task and router representation.
Key results
- T2MIR-AD reaches 90.9 test return on DarkRoom (Mixed), tied with DICP and above AD (57.5) and DPT (72.5).
- T2MIR-DPT achieves -43.2 on Cheetah-Vel (Mixed) vs. -56.1 for DPT and -119.2 for AD.
- T2MIR-AD scores 823.9 on Reach (Mixed), above the best baseline IDT at 808.5.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| add token-wise and task-wise MoE to AD | AD · Cheetah-Vel (Mixed) | test return: -119.2 -> -68.9 | Helped |
| add token-wise and task-wise MoE to DPT | DPT · Cheetah-Vel (Mixed) | test return: -56.1 -> -43.2 | Helped |
| add token-wise and task-wise MoE to AD | AD · Walker-Param (Mixed) | test return: 395.2 -> 435.7 | Helped |
| add token-wise and task-wise MoE to DPT | DPT · Walker-Param (Mixed) | test return: 425.9 -> 492.8 | Helped |
| add token-wise and task-wise MoE to AD | AD · Reach (Mixed) | test return: 790.4 -> 823.9 | Helped |
| add token-wise and task-wise MoE to AD | AD · Push (Mixed) | test return: 604.7 -> 665.8 | Helped |
| add task-wise MoE (ablation) | T2MIR-AD · Cheetah-Vel (Mixed) | test return: -76.1 -> -68.9 | Helped |
| add token-wise MoE (ablation) | T2MIR-AD · Cheetah-Vel (Mixed) | test return: -101.1 -> -68.9 | Helped |
| add task-wise MoE (ablation) | T2MIR-AD · Walker-Param (Mixed) | test return: 418.6 -> 435.7 | Helped |
| add token-wise MoE (ablation) | T2MIR-AD · Walker-Param (Mixed) | test return: 410.8 -> 435.7 | Helped |
| add task-wise MoE (ablation) | T2MIR-DPT · Cheetah-Vel (Mixed) | test return: -49.5 -> -43.2 | Helped |
| add token-wise MoE (ablation) | T2MIR-DPT · Cheetah-Vel (Mixed) | test return: -47.5 -> -43.2 | Helped |
Surprising findings
- DICP outperforms T2MIR on DarkRoom in learning speed and matches its asymptotic return, which the authors attribute to model-based planning in small state-action spaces.
- Ablating the token-wise MoE hurts T2MIR-AD more than ablating the task-wise MoE, while the reverse holds for T2MIR-DPT.
Limitations
- Evaluated only on relatively lightweight benchmark datasets rather than large-scale environments.
- Gains over strong baselines are modest in some tasks (e.g., Point-Robot differences within ~0.5 return).
- Hand-tuned balance loss weights and expert configurations required.
Experimental setup
Datasets: DarkRoom Point-Robot Cheetah-Vel Walker-Param Reach Push Mixed Medium-Expert Medium
Benchmarks: DarkRoom Point-Robot Cheetah-Vel Walker-Param Reach Push
Metrics: test return gradient cosine similarity
Baselines: AD DPT IDT DICP UNICORN
Builds on: Algorithm Distillation Decision-Pretrained Transformer Shazeer sparse MoE MoCo InfoNCE
Closest papers by meaning
- Multi-Task Reinforcement Learning with Mixture of Orthogonal Experts (ICLR 2024 · similarity 0.90)
- Mastering Massive Multi-Task Reinforcement Learning via Mixture-of-Expert Decision Transformer (ICML 2025 · similarity 0.90)
- XLand-100B: A Large-Scale Multi-Task Dataset for In-Context Reinforcement Learning (ICLR 2025 · similarity 0.89)
- Towards Provable Emergence of In-Context Reinforcement Learning (NeurIPS 2025 · similarity 0.89)
- In-Context Decision Transformer: Reinforcement Learning via Hierarchical Chain-of-Thought (ICML 2024 · similarity 0.89)
- Vintix: Action Model via In-Context Reinforcement Learning (ICML 2025 · similarity 0.88)
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