docs/source/metaworld.mdx

# Meta-World

Meta-World is a well-designed, open-source simulation benchmark for multi-task and meta reinforcement learning in continuous-control robotic manipulation. It gives researchers a shared, realistic playground to test whether algorithms can _learn many different tasks_ and _generalize quickly to new ones_ — two central challenges for real-world robotics.

- 📄 [MetaWorld paper](https://arxiv.org/pdf/1910.10897)
- 💻 [Original MetaWorld repo](https://github.com/Farama-Foundation/Metaworld)

![MetaWorld MT10 demo](https://meta-world.github.io/figures/ml45.gif)

## Why Meta-World matters

- **Diverse, realistic tasks.** Meta-World bundles a large suite of simulated manipulation tasks (50 in the MT50 suite) using everyday objects and a common tabletop Sawyer arm. This diversity exposes algorithms to a wide variety of dynamics, contacts and goal specifications while keeping a consistent control and observation structure.
- **Focus on generalization and multi-task learning.** By evaluating across task distributions that share structure but differ in goals and objects, Meta-World reveals whether an agent truly learns transferable skills rather than overfitting to a narrow task.
- **Standardized evaluation protocol.** It provides clear evaluation modes and difficulty splits, so different methods can be compared fairly across easy, medium, hard and very-hard regimes.
- **Empirical insight.** Past evaluations on Meta-World show impressive progress on some fronts, but also highlight that current multi-task and meta-RL methods still struggle with large, diverse task sets. That gap points to important research directions.

## What it enables in LeRobot

In LeRobot, you can evaluate any policy or vision-language-action (VLA) model on Meta-World tasks and get a clear success-rate measure. The integration is designed to be straightforward:

- We provide a LeRobot-ready dataset for Meta-World (MT50) on the HF Hub: `https://huggingface.co/datasets/lerobot/metaworld_mt50`.
  - This dataset is formatted for the MT50 evaluation that uses all 50 tasks (the most challenging multi-task setting).
  - MT50 gives the policy a one-hot task vector and uses fixed object/goal positions for consistency.

- Task descriptions and the exact keys required for evaluation are available in the repo/dataset — use these to ensure your policy outputs the right success signals.

## Quick start, train a SmolVLA policy on Meta-World

Example command to train a SmolVLA policy on a subset of tasks:

```bash
lerobot-train \
  --policy.type=smolvla \
  --policy.repo_id=${HF_USER}/metaworld-test \
  --policy.load_vlm_weights=true \
  --dataset.repo_id=lerobot/metaworld_mt50 \
  --env.type=metaworld \
  --env.task=assembly-v3,dial-turn-v3,handle-press-side-v3 \
  --output_dir=./outputs/ \
  --steps=100000 \
  --batch_size=4 \
  --eval.batch_size=1 \
  --eval.n_episodes=1 \
  --eval_freq=1000
```

Notes:

- `--env.task` accepts explicit task lists (comma separated) or difficulty groups (e.g., `env.task="hard"`).
- Adjust `batch_size`, `steps`, and `eval_freq` to match your compute budget.
- **Gymnasium Assertion Error**: if you encounter an error like
  `AssertionError: ['human', 'rgb_array', 'depth_array']` when running MetaWorld environments, this comes from a mismatch between MetaWorld and your Gymnasium version.
  We recommend using:

```bash
  pip install "gymnasium==1.1.0"
```

to ensure proper compatibility.

## Quick start — evaluate a trained policy

To evaluate a trained policy on the Meta-World medium difficulty split:

```bash
lerobot-eval \
  --policy.path="your-policy-id" \
  --env.type=metaworld \
  --env.task=medium \
  --eval.batch_size=1 \
  --eval.n_episodes=2
```

This will run episodes and return per-task success rates using the standard Meta-World evaluation keys.

## Practical tips

- If you care about generalization, run on the full MT50 suite — it’s intentionally challenging and reveals strengths/weaknesses better than a few narrow tasks.
- Use the one-hot task conditioning for multi-task training (MT10 / MT50 conventions) so policies have explicit task context.
- Inspect the dataset task descriptions and the `info["is_success"]` keys when writing post-processing or logging so your success metrics line up with the benchmark.