XE Arena
Preview · first release in preparation

XE2 Arena

XE2 = cross-embodiment × cross-environment

One agent. Many robot bodies. Real and simulated.

Test LLM robot agents on many bodies, in the real world and in simulation, then train them with the same tools.

How it fits together See real vs sim Paper in preparation Code in preparation
5
embodiments, more coming
12
real tasks
2×
real + replica
400
sim tasks for RL

Built together by

Harvard University
Princeton University
University of California, Berkeley
Robotics Center

What XE means

Cross-embodiment × cross-environment

Same task across bodies. Same run in real and in sim.

YAM pair
xArm pair
xArm + Wuji Hand 2
Humanoid
Mobile manipulator
Real
Recording
Recording
Recording
Coming
Coming
Sim
First replicas
First replicas
First replicas
Coming
Coming

Real vs sim

Every recording gets a replica

Drag to compare the real robot with its replica replaying the same joint motion.

realreplica

YAM pair, 3× speed. First MuJoCo replicas, before the contact work.

One storyline

XEbench
Measure · cross-embodiment

Same task on many real robots.

XEsim
Replicate · cross-environment

Every real run rebuilt in sim.

Robot-RL
Train · same tools, same verifier

Verifier success becomes the reward.

↺ trained agents return to XEbench

XEbenchcross-embodiment · same task, many bodies

Robots

Same task, many bodies

YAM pair

Two 6-DoF arms · parallel grippers

xArm pair

Two arms · parallel grippers

xArm + Wuji Hand 2

Five-finger dexterous hand
Humanoid robot
Humanoid
Mobile manipulator with two arms on a lifting column
Mobile manipulator

More bodies coming next

Humanoid · mobile manipulator · more hands

Tasks

Twelve tasks, from atomic to contact-rich

Three tiers: anchor, middle, frontier.

parallel handsanchor
Sort lollipops and snacks into a plate
parallel handsmiddle
Stack the two outer cups into the middle one
one holds, one actsanchor
Pull the cap off a marker
one holds, one actsmiddle
Uncap and recap a marker
handoveranchor
Hand an object across, then into a box
one holds, one actsmiddle
Hold a test-tube rack and insert a tube
one holds, one actsfrontier
Hold a network switch and plug in an Ethernet cable
soft object, two handsanchor
Fold a T-shirt or towel in half
soft object, two handsmiddle
Fold a towel twice
soft object, two handsfrontier
Fold a T-shirt
rigid object, two handsanchor
Carry an empty tray, keeping it level
rigid object, two handsmiddle
Carry a tray with a cup on it

More tasks coming

planned

Harder

  • Unscrew a jar lid
  • Pour into a cup without spilling
  • Route a cable through clips
  • Fold a T-shirt and stack it

Several robots together

  • A humanoid and a mobile manipulator tidy a room together
  • Two robots carry a long board
  • Pass an object between stations
  • Assembly line: open, pack, close a box

Inside the lab

Same brain, different bodies

Four models, three real arms, one task: put a brick in a box.

20× speed. Pilot runs from eval.roboticscenter.ai, not XEbench scores.

XEsimcross-environment · every recording gets a replica

How a replica is built

Robot logs

Controller parameters

Video

Camera calibration

Real scene

Object poses, background

Replay + compare

MuJoCo or IPC contact

A replica is useful when it ranks agents in the same order as the real robot. See the comparison ↑

Run protocol

Same prompt, same tools, same verifier

Only the backend changes between a real run and its replica.

MCP tool call · same on real and sim
{
  "name": "move_to",
  "arguments": {
    "observation_id": "obs_0042",
    "command_id": "cmd_0043",
    "note": "lift the cup 5 cm",
    "frame": "base",
    "translation_m": [0.0, 0.0, 0.05],
    "rotation_delta_rad": [0.0, 0.0, 0.0]
  }
}
eval.yaml · swap the backend
agent: cc              # cc · codex · dsh
profile: intuitive     # or expert
engine:
  kind: robosuite      # replica in sim
  # kind: real         # the real station
  task: cup_stack
  command_budget: 80
smoke test · real Claude Code CLI + simulated MCP robot + local fake model, no API calls
$ ./scripts/run.sh demo \
    --agent cc \
    --claude .tools/claude-2.1.296/claude \
    --provider openai
# → "demo_verified": true

Agent harness

Claude Code · Codex · DeepSeek Harness

Robot tools over MCP

intuitive: 5 tools · expert: 16

Real robot or replica

Same tool calls, either backend

Separate verifier

Scores the final state

Robot-RLtrain · same tools, same verifier

The arena is also a training environment

The verifier that scores a run is the reward that trains the agent.

Task + prompt Agent harness MCP tools Sim or real Verifier Reward → GRPO Robot-RL one loop, eval and training
replica · 12×

Next: XEsim replicas as training environments.

5 / 16tools: intuitive / expert
4engines: MuJoCo · Newton · OvPhysX · real
400Tabletop400 training tasks
27BQwen3.8 GRPO recipe
launch GRPO on Qwen3.8-27B · GPU topology is just arguments
$ bash examples/train_qwen38_27b.sh --dry-run \
    --actor-num-nodes 2 --actor-num-gpus-per-node 4 \
    --rollout-num-gpus 4 \
    --tensor-model-parallel-size 2 --pipeline-model-parallel-size 2 \
    --rollout-batch-size 8 --n-samples-per-prompt 8
# review the generated command, then drop --dry-run

Runs in simulation today. A full 27B training step is not yet verified.

Status

Where things stand

real

Robot runs

Recordings on YAM, xArm and Wuji Hand 2.

replica

Contact physics

IPC holds the cups; cloth close, not matched yet.

benchmark

Scores

No paired real and sim scores yet.

training

Robot-RL

Runs in sim; full 27B step pending.

Related benchmarks

What is new here

BenchmarkTestsCross-embodimentCross-environment
Embodied First Examcoding agentsyessim only
Ember-0 (XDOF)frontier LLMsone robot typereal only
RoboDojolearned policiestasks differ per platformseparate task sets
DuoBenchlearned policiesone robot4 of 11 tasks
SO-101 Benchlearned policies, one LLM agentone armyes, Isaac Lab twin
LIBEROlearned policiesone arm (Franka)sim only
RoboCasalearned policiesseveral robots, one simsim only
RoboTwin 2.0learned policies5 dual-arm robotssim only
BEHAVIOR-1Klearned policiesa few mobile manipulatorssim only
XE2 ArenaLLM agents + RL trainingfive embodiments, more cominga replica per recording

Contact

Run your model on XE2 Arena

Want your agent or policy on our robots and replicas, or want to collaborate? Talk to our researchers.