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Open-weight model · Robotics

MolmoAct2-LIBERO

by Ai2 allenai/MolmoAct2-LIBERO

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.

Parameters5.4B
Context16,384
Weights21.8 GB
License
AccessOpen weights
Monthly Downloads6.7k

Runs On

What it takes to serve MolmoAct2-LIBERO (5.4B parameters): the memory its weights need at each precision, and the cheapest way to rent enough data-center GPUs to hold them.

PrecisionWeightsMemory neededCheapest setupPer hourAlso 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 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…

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-LIBERO
Publisher
Ai2
Task
Robotics
Modality
Control
Library
transformers
Parameters
5.4B parameters
Languages
Not stated by the source
Revision
0d24a92bd1faf321ef497c3bbd5681af97c65aa2
First published
2026-05-04
Last updated
2026-05-23

Files and Weights

24 files, 21.8 GB in total. The weights are 5 files totalling 21.8 GB in safetensors.

Weights5 files · 21.8 GB
Configuration11 files · 458.0 KB
Tokenizer2 files · 12.0 MB
Documentation1 file · 8.0 KB
Other4 files · 141.2 KB
Repository1 file · 1.6 KB
Every file
FileTypeSizeSHA-256
model-00001-of-00005.safetensorsWeights4.9 GB 5aa56113a3c1
model-00002-of-00005.safetensorsWeights4.8 GB 1fd95aec9ad1
model-00003-of-00005.safetensorsWeights4.8 GB e6c455434915
model-00004-of-00005.safetensorsWeights4.9 GB 4e5bcf5bad81
model-00005-of-00005.safetensorsWeights2.3 GB 76140ad00c22
config.jsonConfiguration4.3 KB
configuration_molmoact2.pyConfiguration20.7 KB
generation_config.jsonConfiguration116 B
image_processing_molmoact2.pyConfiguration22.4 KB
inference.pyConfiguration25.9 KB
model.safetensors.index.jsonConfiguration131.5 KB
modeling_molmoact2.pyConfiguration191.0 KB
norm_stats.jsonConfiguration5.8 KB
processing_molmoact2.pyConfiguration17.3 KB
processor_config.jsonConfiguration1.9 KB
video_processing_molmoact2.pyConfiguration37.2 KB
README.mdDocumentation8.0 KB
assets/MolmoAct2.svgOther7.6 KB
assets/sample_agentview_rgb.pngOther65.2 KB
assets/sample_wrist_rgb.pngOther65.3 KB
chat_template.jinjaOther3.2 KB
.gitattributesRepository1.6 KB
tokenizer.jsonTokenizer12.0 MB d5395aefc9b1
tokenizer_config.jsonTokenizer782 B

License and Download

License
Not stated by the source
Access
Open weights, no gate
Download size
21.8 GB
Download from Ai2

Released by Ai2 through its official repository on Hugging Face.

Built From

Memory Requirements

PrecisionWeights in memory
As published21.8 GB
16-bit10.9 GB
8-bit5.4 GB
4-bit2.7 GB

Weights only, from the published parameter count; the key-value cache and runtime add to this.

Questions About MolmoAct2-LIBERO

How much GPU memory does MolmoAct2-LIBERO 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-LIBERO 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-LIBERO's context length?

16,384 tokens, from the maximum position embeddings in its published configuration.

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