Model release

ESMC 6B (ESM Cambrian)

ESMC 6B (ESM Cambrian) is an open-weight model release in the ESM (EvolutionaryScale and Biohub protein models) family from Biohub (Chan Zuckerberg Biohub, Inc.)1 3 4 and EvolutionaryScale (original developer; now part of Biohub)7 9, version ESMC-6B (esmc-6b-2024-12 on the Biohub Platform API), released May 2026. Its weights can be downloaded by the public1 2 under the MIT License1 3 4.

The largest ESM C (ESM Cambrian) protein language model: 6 billion parameters, 80 transformer layers, and 2.37e23 training FLOPs. EvolutionaryScale introduced ESM C in December 2024; Biohub's May 2026 release of ESMC, ESMFold2, and ESM Atlas included the 6B weights, and ESMFold2 is trained on top of a frozen ESMC 6B.1 7 3 6

Model hub: Model card (Hugging Face) (external site: huggingface.co)
Repository: GitHub repository (Biohub/esm) (external site: github.com)
Paper: ESMC and ESMFold2 preprint (bioRxiv) (external site: biorxiv.org)

On AI on Hugging Face: biohub/ESMC-6B

Last reviewedSep 29, 2026Entry updated Sep 29, 2026Documented release May 2026

Availability and license

Overall availability

Public

Downloadable from Hugging Face without gating. The card lists uses prohibited by Biohub's Acceptable Use Policy as out of scope.1 2

Availability fact review: not separately recorded

Availability is separate from permission: read the license before using or redistributing.

MIT License (external site: raw.githubusercontent.com)1 3 4
Applies to: Weights and code · SPDX MIT · on the rubric’s OSI-approved software-license list · fact-level rights review not recorded
Plain-language guide to the MIT License

The card's license field lists "mit" and "other", with the license link pointing to the repository's third-party notice, which lists the licenses of code dependencies such as PyTorch, flash-attn, and xformers. The repository README states the models are available under the MIT license and asks users to follow Biohub's Acceptable Use Policy. EvolutionaryScale's December 2024 ESM C post, as archived on 2024-12-05, released the 300M and 600M weights and offered ESM C 6B through its Forge API and AWS SageMaker, while the current version of that post states that all three sizes were released as open weights under the MIT license.1 5 3 8 7

Component reuse rights

A readable or downloadable component is not automatically reusable. These indicators concern recorded license evidence, not system certification.

weights: Unknown — no complete fact-level rights review
code: Unknown — no complete fact-level rights review
data: Unknown — no complete fact-level rights review
documentation: Unknown — no complete fact-level rights review

No complete system-rights review is recorded for this release.

Model-disclosure tier

Computed from the checklist below using USASI rubric v0.2. An editorial category, not a certification.

Open-weight

The model parameters for this release can be downloaded by the public. License terms may still restrict use, redistribution, or commercial use.

How tiers are computed

Public materials checklist

Items for a model under USASI rubric v0.2. Unknown means unassessed or insufficient evidence.

Public materials checklist for ESMC 6B (ESM Cambrian)
Item	Status	Notes and evidence
WeightsCan the general public download the model parameters for this release?	Public	Downloadable from Hugging Face without gating.1 2
Inference codeIs code for running the model published?	Public	The card documents loading the model with Hugging Face Transformers, and the esm package provides the production inference path.1 3
Training codeIs the code used to train the model published?	Unknown	No ESM C training code was identified in the pages reviewed.
Training-data informationDoes the information cover provenance, scope, acquisition, selection, labeling, processing, and where data or alternatives can be obtained? Access alone does not establish completeness.	Unknown	Not assessed.
Training-data accessCan the training data be obtained? This is independent of information completeness and reuse rights; original unshareable data need not be downloadable.	Unknown	Not assessed.
Complete training pipelineIs the complete base-training and preprocessing pipeline published, including configuration? Fine-tuning code or an inference SDK alone is insufficient.	Unknown	Not assessed.
Legacy data assessment (v0.1)Historical assessment combining download access and disclosure. Preserved for traceability; excluded from the v0.2 tier calculation. See the new separate assessments above.	Partial	The card names the sources (UniRef, MGnify, and JGI sequences clustered at 70% identity into 83M, 372M, and 2B clusters) but does not provide the training set itself.1
Training recipeAre the training configuration and procedure documented in enough detail to follow?	Partial	The card describes two stages: 1 million steps at 512-token context with 64% metagenomic data, then 500,000 steps at 2,048-token context with 37.5% metagenomic data. Further details are in the preprint, which was not reviewed.1
Evaluation materialsPublic = evaluation code or prompts that let others re-run the evaluations are published. Partial = results only.	Unknown	The card refers to the preprint for performance metrics; the preprint was not reviewed.

What it is useful for

Producing protein representations and embeddings for downstream tasks such as protein engineering and variant effect prediction, and fine-tuning for token or sequence classification; the card also points to sparse autoencoders for interpreting its features.1 3

Run and use notes

Documented facts only. No hardware or performance claims are made without a cited source and stated assumptions.

The card documents inference with Hugging Face Transformers (AutoModelForMaskedLM) and recommends a GPU; using the flash attention backend requires running the model in bfloat16. The context window is 2,048 tokens.1

Organization context

Provenance and derivatives

Trained on protein sequences from public databases (UniRef and MGnify) and the Joint Genome Institute. The 300M and 600M ESM C models are separate, smaller variants released alongside it.1 7

Other releases in the ESM (EvolutionaryScale and Biohub protein models) family

ESM3 open small (esm3-sm-open-v1)Model-disclosure tier (USASI rubric v0.2): Open-weight

ESM (EvolutionaryScale and Biohub protein models) family overview

What this catalog does not know

Unknown means the sources reviewed for this record do not document it. It is not evidence that something does not exist.

Training code: unknown.
Training-data information: unknown.
Training-data access: unknown.
Complete training pipeline: unknown.
Evaluation materials: unknown.

Have a primary source? How to report a correction.

U.S. eligibility

Project eligibility rests on documented governing or maintaining entities, not on contributors.

Eligible · basis: U.S.-governed project

ESM C was introduced by EvolutionaryScale, PBC (New York address in its former terms of use, effective January 15, 2025), and the 6B weights are published by Biohub, whose repository license names Chan Zuckerberg Biohub, Inc. The IRS lists Chan Zuckerberg Biohub Inc in Redwood City, California as a 501(c)(3) organization.7 10 1 4 11

Assessed Sep 29, 2026

Sources

1.
biohub/ESMC-6B model card (external site: huggingface.co)
Biohub · Model card · accessed Sep 29, 2026
2.
biohub/ESMC-6B (Hugging Face model API metadata) (external site: huggingface.co)
Hugging Face · Other · accessed Sep 29, 2026
3.
Biohub/esm README (formerly evolutionaryscale/esm) (external site: github.com)
Biohub · Repository · accessed Sep 29, 2026
4.
Biohub/esm LICENSE.md (external site: raw.githubusercontent.com)
Chan Zuckerberg Biohub, Inc. · License · accessed Sep 29, 2026
5.
Biohub/esm THIRD_PARTY_NOTICE.md (external site: raw.githubusercontent.com)
Biohub · License · accessed Sep 29, 2026
6.
Biohub releases a world model of protein biology (external site: biohub.org)
Biohub · Announcement · published May 27, 2026 · accessed Sep 29, 2026
7.
ESM Cambrian: Revealing the mysteries of proteins with unsupervised learning (external site: evolutionaryscale.ai)
EvolutionaryScale · Announcement · published Dec 4, 2024 · accessed Sep 29, 2026
8.
ESM Cambrian: Revealing the mysteries of proteins with unsupervised learning (Internet Archive snapshot, 2024-12-05) (external site: web.archive.org)
EvolutionaryScale (archived by the Internet Archive) · Announcement · published Dec 4, 2024 · accessed Sep 29, 2026
9.
EvolutionaryScale (home page) (external site: evolutionaryscale.ai)
EvolutionaryScale · Official page · accessed Sep 29, 2026
10.
Terms of Use (historical) | EvolutionaryScale (external site: evolutionaryscale.ai)
EvolutionaryScale · Official page · accessed Sep 29, 2026
11.
Exempt Organizations Business Master File Extract - California (eo_ca.csv) (external site: irs.gov)
Internal Revenue Service · Filing · accessed Sep 29, 2026

Email a correction Report a correction Edit this entry

This listing is not an endorsement, a safety assessment, or a federal approval.

Cite this page

APA style

USASI. (2026, September 29). ESMC 6B (ESM Cambrian). United States of America Superintelligence. https://unitedstatesofamericasuperintelligence.com/open/esmc-6b/

BibTeX

@misc{usasi_esmc_6b,
  author = {{USASI}},
  title = {ESMC 6B (ESM Cambrian)},
  year = {2026},
  month = sep,
  howpublished = {\url{https://unitedstatesofamericasuperintelligence.com/open/esmc-6b/}},
  note = {United States of America Superintelligence. Last updated 2026-09-29}
}

The date is when this page was last updated. Add the date you read it if your style needs one.

For maintainers: a “Listed in USASI” badge

Links to this page. It says the entry is listed, not endorsed or rated. About the badge

Markdown (for a README)

[![Listed in the USASI catalog](https://unitedstatesofamericasuperintelligence.com/badges/listed.svg)](https://unitedstatesofamericasuperintelligence.com/open/esmc-6b/)

HTML

<a href="https://unitedstatesofamericasuperintelligence.com/open/esmc-6b/"><img src="https://unitedstatesofamericasuperintelligence.com/badges/listed.svg" alt="Listed in the USASI catalog" height="20"></a>