MolmoAct2 is an open vision-language-action model for robot control. It builds on Molmo2-ER, an embodied-reasoning VLM backbone, and connects the autoregressive VLM to a flow-matching continuous action expert through per-layer KV (key-value) conditioning. This checkpoint is the post-trained, multi-embodiment MolmoAct2 model. It is intended as a foundation checkpoint for further robot fine-tuning rather than as a ready-to-run policy for a single deployment setting. Use this checkpoint for further fine-tuning on a target robot embodiment or benchmark. It contains the VLM and continuous action expert weights, plus normalization metadata for the post-training mixture in normstats.json. This…
MolmoAct2 is an open vision-language-action model for robot control. It builds on Molmo2-ER and attaches a flow-matching continuous action expert that conditions on the VLM key-value cache through a per-layer connection.
Runs On
What it takes to serve MolmoAct2-BimanualYAM (5.4B parameters): the memory its weights need at each precision, and the cheapest way to rent enough data-center GPUs to hold them.
| Precision | Weights | Memory needed | Cheapest setup | Per hour | Also fits |
|---|---|---|---|---|---|
| 16-bit | 10.9 GB | 13.1 GB | 1x MI300X (192 GB) Vultr |
$1.85 | 1x H100 $1.99 · 1x MI325X $2.00 |
| 8-bit | 5.4 GB | 6.5 GB | 1x MI300X (192 GB) Vultr |
$1.85 | 1x H100 $1.99 · 1x MI325X $2.00 |
| 4-bit | 2.7 GB | 3.3 GB | 1x MI300X (192 GB) Vultr |
$1.85 | 1x H100 $1.99 · 1x MI325X $2.00 |
Memory is the weights at that precision plus 20% for the runtime and a short context; a long context needs more. Prices are the lowest on-demand hourly rates in the SAVRN Index, read Sep 18, 2026.
Model Card
MolmoAct2 is an open vision-language-action model for robot control. It builds on Molmo2-ER and attaches a flow-matching continuous action expert that conditions on the VLM key-value cache through a per-layer connection. This checkpoint is fine-tuned on the bimanual YAM mixture with absolute joint-pose control and annotated language instructions. It is intended for both further fine-tuning and bimanual YAM policy inference. Use this checkpoint for bimanual YAM inference or for further fine-tuning. Dataset normalization metadata is stored in normstats.json. pass normtag="yamdualmolmoact2" at inference time. Continuous action prediction is the intended and recommended inference mode. Discrete…
Excerpt from the card by Ai2.
Configuration
- Architecture
- MolmoAct2ForConditionalGeneration
- Context length (tokens)
- 16,384
- Layers
- 36
- Hidden size
- 2,560
- Feed-forward size
- 9,728
- Attention heads
- 32
- Key/value heads
- 8
- Head dimension
- 128
- Vocabulary size
- 154,624
- RoPE base
- 5e+06
- Model type
- molmoact2
Identity and Version
- Repository
- allenai/MolmoAct2-BimanualYAM
- Publisher
- Ai2
- Task
- Robotics
- Modality
- Control
- Library
- transformers
- Parameters
- 5.4B parameters
- Languages
- Not stated by the source
- Revision
- 8dcbed66f2380e4393189c303ea72488eb9e63c2
- First published
- 2026-05-04
- Last updated
- 2026-05-23
Files and Weights
25 files, 21.8 GB in total. The weights are 5 files totalling 21.8 GB in safetensors.
Every file
| File | Type | Size | SHA-256 |
|---|---|---|---|
| model-00001-of-00005.safetensors | Weights | 4.9 GB | af779f7c1f75 |
| model-00002-of-00005.safetensors | Weights | 4.8 GB | cb9d302e9030 |
| model-00003-of-00005.safetensors | Weights | 4.8 GB | 72b928892f06 |
| model-00004-of-00005.safetensors | Weights | 4.9 GB | 5c828fa227dc |
| model-00005-of-00005.safetensors | Weights | 2.3 GB | 9af4e86a0cc0 |
| config.json | Configuration | 4.3 KB | — |
| configuration_molmoact2.py | Configuration | 20.7 KB | — |
| generation_config.json | Configuration | 116 B | — |
| image_processing_molmoact2.py | Configuration | 22.4 KB | — |
| inference.py | Configuration | 25.9 KB | — |
| model.safetensors.index.json | Configuration | 131.5 KB | — |
| modeling_molmoact2.py | Configuration | 191.0 KB | — |
| norm_stats.json | Configuration | 10.2 KB | — |
| processing_molmoact2.py | Configuration | 17.3 KB | — |
| processor_config.json | Configuration | 1.9 KB | — |
| video_processing_molmoact2.py | Configuration | 37.2 KB | — |
| README.md | Documentation | 8.7 KB | — |
| assets/MolmoAct2.svg | Other | 7.6 KB | — |
| assets/sample_left_rgb.png | Other | 215.3 KB | 2908fecaae08 |
| assets/sample_right_rgb.png | Other | 254.7 KB | 12c966772cd1 |
| assets/sample_top_rgb.png | Other | 453.3 KB | 3d42e26d70ab |
| chat_template.jinja | Other | 3.2 KB | — |
| .gitattributes | Repository | 1.8 KB | — |
| tokenizer.json | Tokenizer | 12.0 MB | d5395aefc9b1 |
| tokenizer_config.json | Tokenizer | 782 B | — |
License and Download
- License
- Not stated by the source
- Access
- Open weights, no gate
- Download size
- 21.8 GB
Released by Ai2 through its official repository on Hugging Face.
Built From
- Described by arXiv:2605.02881
Memory Requirements
| Precision | Weights in memory |
|---|---|
| As published | 21.8 GB |
| 16-bit | 10.9 GB |
| 8-bit | 5.4 GB |
| 4-bit | 2.7 GB |
Weights only, from the published parameter count; the key-value cache and runtime add to this.
Questions About MolmoAct2-BimanualYAM
How much GPU memory does MolmoAct2-BimanualYAM need?
About 13.1 GB at 16-bit and 3.3 GB at 4-bit: the weights (5.4B parameters) plus a working margin. A long context needs more.
What is the cheapest GPU to run MolmoAct2-BimanualYAM on?
At 16-bit, 1x MI300X from $1.85 an hour; at 4-bit, 1x MI300X from $1.85 an hour, at the lowest on-demand prices the SAVRN Index lists.
What is MolmoAct2-BimanualYAM's context length?
16,384 tokens, from the maximum position embeddings in its published configuration.
Similar Models
MolmoAct2 is an open vision-language-action model for robot control. It builds on Molmo2-ER and attaches a flow-matching continuous action expert that conditions on the VLM key-value cache through a per-layer connection. This checkpoint is fine-tuned on the SO-100/101 mixture with absolute joint-pose control and annotated language instructions. It is intended for both further fine-tuning and SO-100/101 policy inference. Use this checkpoint for SO-100/101 inference or for further fine-tuning. Dataset normalization metadata is stored in normstats.json. pass normtag="so100so101molmoact2" at inference time. Continuous action prediction is the intended and recommended inference mode. Discrete…
MolmoAct2 is an open vision-language-action model for robot control. It builds on Molmo2-ER and attaches a flow-matching continuous action expert that conditions on the VLM key-value cache through a per-layer connection. This checkpoint is fine-tuned on the full LIBERO training mixture, combining Spatial, Object, Goal, and Long suites. It is intended for both further fine-tuning and LIBERO policy inference. Use this checkpoint for LIBERO inference or for further fine-tuning. Dataset normalization metadata is stored in normstats.json. pass normtag="libero" at inference time. Continuous action prediction is the intended and recommended inference mode. Discrete action prediction is exposed for…
MolmoAct2-Think extends MolmoAct2 with depth-token reasoning. Before producing an action, the model can predict a compact 10 x 10 discrete depth representation and condition the action expert on the resulting depth-aware VLM cache. This checkpoint is the post-trained, multi-embodiment depth-reasoning model. It is intended as a foundation checkpoint for further robot fine-tuning rather than as a ready-to-run policy for a single deployment setting. Use this checkpoint for further fine-tuning when the downstream policy should use depth reasoning. It contains the VLM, action expert, and depth-token weights, plus normalization metadata for the post-training mixture in normstats.json. This model…
This policy has been trained and pushed to the Hub using LeRobot. See the full documentation at LeRobot Docs. For a complete walkthrough, see the training guide. Below is the short version on how to train and run inference/eval: Writes checkpoints to outputs/train/ /checkpoints/. Prefix the dataset repo with eval\ and supply --policy.path pointing to a local or hub checkpoint.
This policy has been trained and pushed to the Hub using LeRobot. See the full documentation at LeRobot Docs. For a complete walkthrough, see the training guide. Below is the short version on how to train and run inference/eval: Writes checkpoints to outputs/train/ /checkpoints/. Prefix the dataset repo with eval\ and supply --policy.path pointing to a local or hub checkpoint.