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Letting a robot invent its own practice tasks adds 20.6 points of task success

Notes on Playful Agentic Robot Learning (arXiv:2606.19419) — Junyi Zhang, Jiaxin Ge, H. Yoo, Letian Fu, Zihan Yang, Yao Liu, R. Saravanan, Shaofeng Yin, Justin Yu, Dantong Niu, Zirui Wang, Roei Herzig, and 8 more · June 2026

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RATs (Robotics Agent Teams) gives a robot a practice stage before it's ever handed a task — a multi-agent Code-as-Policy system built around three coordinating roles. A task proposer invents exploratory goals, an execution team writes and runs candidate robot code with step-level verification and retry-on-failure, and a memory team distills what worked into a persistent skill library. Task selection isn't random: a "Goldilocks" score multiplies novelty (how rarely a given object-skill pairing has been attempted) by learnability (how close the agent's current success rate on that skill sits to 50%), pushing practice toward the edge of what the agent can already half-do. It's intrinsic motivation from developmental psychology, rebuilt as a computable scoring function instead of a vague heuristic.

After 50 play iterations per environment, the resulting skill libraries lifted held-out task success from 23.2% to 43.8% on LIBERO-PRO (+20.6 points) and from 21.0% to 38.0% on MolmoSpaces (+17.0 points) — both well clear of the strongest vision-language-action baseline tested, π0.5, which topped out at 12.8%. The skills traveled, too: plugging the LIBERO-PRO library into an otherwise unmodified baseline agent raised RoboSuite success from 40.3% to 49.1%, and the same frozen library pushed real-robot pick-and-place from 30.0% to 38.8%, with no real-world play and no model finetuning — a form of sim-to-real transfer achieved purely by retrieving code into context. An ablation shows where the gain actually comes from: swap curiosity-driven task selection for randomly sampled tasks under the identical 50-iteration budget and the number barely moves, 23.2% to 24.7%, while curiosity-driven selection alone reaches 32.3%. What the agent chooses to practice is doing the work, not how much it practices.

Key numbers

LIBERO-PRO task success (play-learned skills)23.2% → 43.8% (+20.6 pp)
MolmoSpaces task success21.0% → 38.0% (+17.0 pp)
Cross-sim transfer to RoboSuite40.3% → 49.1% (+8.9 pp)
Real-robot transfer, no finetuning30.0% → 38.8% (+8.8 pp)
Random play vs. curiosity-driven play24.7% vs. 32.3%

Skills related to this research

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References

  1. J. Zhang, J. Ge, H. Yoo, L. Fu, et al. Playful Agentic Robot Learning. arXiv:2606.19419, 2026.
  2. M. Fu, J. Yu, K. El-Refai, et al. CaP-X: A framework for benchmarking and improving coding agents for robot manipulation. arXiv:2603.22435, 2026.
  3. G. Wang, Y. Xie, Y. Jiang, et al. Voyager: An open-ended embodied agent with large language models. Transactions on Machine Learning Research (TMLR), 2024.
  4. Y. Zhu, J. Wong, A. Mandlekar, et al. robosuite: A modular simulation framework and benchmark for robot learning. arXiv:2009.12293, 2020.
  5. Y. Kim, W. Pumacay, O. Rayyan, et al. MolmoSpaces: A large-scale open ecosystem for robot navigation and manipulation. arXiv:2602.11337, 2026.