Ai2 Open-Sources MolmoAct 2 Robot Foundation Model, Outperforms Physical Intelligence π0.5

The Allen Institute for AI (Ai2) fully open-sourced MolmoAct 2 on May 5, 2026 — releasing model weights, training code, and complete training data simultaneously. The 7B-parameter robot foundation model outperforms Physical Intelligence's closed-source π0.5 across simulation and real-world benchmarks.

Performance

On real-world DROID tasks in zero-shot settings, MolmoAct 2 achieves up to 87.1% success. Task-level numbers:

Apple-to-plate transfer: 100% success

Pipette-to-tray: 86.7% success

Multi-step object sorting: 62% success

Architecture

MolmoAct 2 couples the Molmo 2-ER vision-language model with a dedicated action expert using flow matching, connected via a KV-cache bridge. This design delivers a 37× inference speedup over prior architectures.

Open Dataset

Training uses 12,000 real-world robot episodes. Ai2 also released MolmoAct 2-Bimanual YAM, a massive open-source bimanual tabletop manipulation dataset with over 700 hours of demonstrations.

Details are in the Ai2 blog post and arXiv paper.