Structure prediction using Boltz-1/Boltz-2, an open biomolecular structure predictor.

MITAuto-check passedResearch & Science

Install Boltz

skills CLI
$ npx skills add adaptyvbio/protein-design-skills --skill boltz -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install adaptyvbio/protein-design-skills boltz --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/adaptyvbio/protein-design-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/boltz .claude/skills/boltz && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
boltz
GitHub stars
163
Used in
4 other repos
Token cost
~1.3k tokens
SKILL.md length
336 words
Files
1
Skills in repo
24
Repo updated
First seen
Licence
MIT

At a glance

Structure prediction using Boltz-1/Boltz-2, an open biomolecular structure predictor.

  • Predicting protein complex structures
  • SKILL.md covers Prerequisites, How to run, Key parameters and FASTA Format, plus 7 more sections
  • Calls modal and pip
  • Validating designed binders

What it does

Boltz is an agent skill from adaptyvbio/protein-design-skills. Structure prediction using Boltz-1/Boltz-2, an open biomolecular structure predictor. Use this skill when: (1) Predicting protein complex structures, (2) Validating designed binders, (3) Need open-source alternative to AF2, (4) Predicting protein-ligand complexes, (5) Using local GPU resources. For QC thresholds, use protein-qc. For AlphaFold2 prediction, use alphafold. For Chai prediction, use chai.

Its SKILL.md is about 1.3k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Research & Science, covering Protein structure and design. It works with AlphaFold. The repository describes itself as: Claude Code skills for protein design. The licence is MIT.

When your agent uses it

  • Predicting protein complex structures
  • Validating designed binders
  • Need open-source alternative to AF2
  • Predicting protein-ligand complexes

Example prompts

  • “/boltz”

Requirements

  • Python 3

What it can do on your machine

Read from SKILL.md and the folder at commit 59dd633. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • modal
    • pip

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md. Its commands use pip, which can reach the network depending on how they are called.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Boltz loads about 1.3k tokens when it runs. Until then it costs about 102 tokens; SKILL.md has 336 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~102
When it runs · the whole SKILL.md, loaded when a task matches
~1.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from adaptyvbio/protein-design-skills at commit 59dd633, republished under its MIT licence (© adaptyvbio). 336 words, ~1,271 tokens.

Download SKILL.mdSave it as .claude/skills/boltz/SKILL.md (or your agent's skills folder).
name
boltz
description
Structure prediction using Boltz-1/Boltz-2, an open biomolecular structure predictor. Use this skill when: (1) Predicting protein complex structures, (2) Validating designed binders, (3) Need open-source alternative to AF2, (4) Predicting protein-ligand complexes, (5) Using local GPU resources. For QC thresholds, use protein-qc. For AlphaFold2 prediction, use alphafold. For Chai prediction, use chai.
license
MIT
category
design-tools
tags
structure-prediction, validation, open-source
biomodals_script
modal_boltz.py

Boltz Structure Prediction

Prerequisites

RequirementMinimumRecommended
Python3.10+3.11
CUDA12.0+12.1+
GPU VRAM24GB48GB (L40S)
RAM32GB64GB

How to run

First time? See Getting started to set up Modal and biomodals.

Option 1: Modal
bash
cd biomodals
modal run modal_boltz.py \
  --input-faa complex.fasta \
  --out-dir predictions/

GPU: L40S (48GB) | Timeout: 1800s default

Option 2: Local installation
bash
pip install boltz

boltz predict \
  --fasta complex.fasta \
  --output predictions/

Key parameters

ParameterDefaultRangeDescription
--recycling_steps31-10Recycling iterations
--sampling_steps20050-500Diffusion steps
--use_msa_servertrueboolUse MSA server

FASTA Format

>protein_A
MKTAYIAKQRQISFVK...
>protein_B
MVLSPADKTNVKAAWG...

Output format

predictions/
├── model_0.cif       # Best model (CIF format)
├── confidence.json   # pLDDT, pTM, ipTM
└── pae.npy          # PAE matrix

Note: Boltz outputs CIF format. Convert to PDB if needed:

python
from Bio.PDB import MMCIFParser, PDBIO
parser = MMCIFParser()
structure = parser.get_structure("model", "model_0.cif")
io = PDBIO()
io.set_structure(structure)
io.save("model_0.pdb")

Comparison

FeatureBoltz-1Boltz-2AF2-Multimer
MSA-free modeYesYesNo
DiffusionYesYesNo
SpeedFastFasterSlower
Open sourceYesYesYes

Sample output

Successful run
$ boltz predict --fasta complex.fasta --output predictions/
[INFO] Loading Boltz-1 weights...
[INFO] Predicting structure...
[INFO] Saved model to predictions/model_0.cif

predictions/confidence.json:
{
  "ptm": 0.78,
  "iptm": 0.65,
  "plddt": 0.81
}

What good output looks like:

  • pTM: > 0.7 (confident global structure)
  • ipTM: > 0.5 (confident interface)
  • pLDDT: > 0.7 (confident per-residue)
  • CIF file: ~100-500 KB for typical complex

Decision tree

Should I use Boltz?
│
├─ What are you predicting?
│  ├─ Protein-protein complex → Boltz ✓ or Chai or ColabFold
│  ├─ Protein + ligand → Boltz ✓ or Chai
│  └─ Single protein → Use ESMFold (faster)
│
├─ Need MSA?
│  ├─ No / want speed → Boltz ✓
│  └─ Yes / maximum accuracy → ColabFold
│
└─ Why Boltz over Chai?
   ├─ Open weights preference → Boltz ✓
   ├─ Boltz-2 speed → Boltz ✓
   └─ DNA/RNA support → Consider Chai

Typical performance

Campaign SizeTime (L40S)Cost (Modal)Notes
100 complexes30-45 min~$8Standard validation
500 complexes2-3h~$35Large campaign
1000 complexes4-6h~$70Comprehensive

Per-complex: ~15-30s for typical binder-target complex.


Verify

bash
find predictions -name "*.cif" | wc -l  # Should match input count

Troubleshooting

Low confidence: Increase recycling_steps OOM errors: Use MSA-free mode or A100-80GB Slow prediction: Reduce sampling_steps

Error interpretation
ErrorCauseFix
RuntimeError: CUDA out of memoryComplex too largeUse --use_msa_server false or larger GPU
KeyError: 'iptm'Single chain onlyEnsure FASTA has 2+ chains
FileNotFoundError: weightsMissing modelRun boltz download first
ValueError: invalid residueNon-standard AACheck for modified residues in sequence
Boltz-1 vs Boltz-2
AspectBoltz-1Boltz-2
SpeedFastFaster
AccuracyGoodImproved, notably antibody-antigen
LigandsBasicBetter support
Affinity predictionNoYes (small-molecule binding)
Release20242025

Boltz-2 is the current default. Boltz-1 is still used where a design pipeline inverts the v1 model.

Affinity prediction (Boltz-2)

Boltz-2 adds an affinity-prediction module that approaches free-energy-perturbation accuracy at a fraction of the cost. It is trained on small-molecule binding data, so use it for protein-ligand and small-molecule work. It does not predict protein-protein binding affinity; for protein binders, rely on interface confidence (ipTM, ipSAE) instead.


Next: protein-qc for filtering and ranking.

© adaptyvbio, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/boltz of adaptyvbio/protein-design-skills.

Open the folder on GitHubat commit 59dd633

Used in 4 other repositories

We found 6 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 4 other GitHub owners. This page covers the copy in adaptyvbio/protein-design-skills, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Boltz next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Boltz compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Boltz this skilladaptyvbio/protein-design-skills1634 repos~1.3kAutomated safety check: PassMIT
Alphafold Database Fetch And Analyzegoogle-deepmind/science-skills3.2k2 repos~1.2kAutomated safety check: PassApache-2.0
Biopipelineslocbp-uzh/biopipelines109—~2.4kAutomated safety check: PassMIT
Bio DB ToolsDrugClaw/DrugClaw125—~1.4kAutomated safety check: PassApache-2.0
Ggetdavila7/claude-code-templates32k11 repos~6.3kAutomated safety check: PassMIT
Alphafold Databasedavila7/claude-code-templates32k10 repos~4kAutomated safety check: PassMIT

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  • Chai

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Works with

Questions about Boltz

What does Boltz do?

Structure prediction using Boltz-1/Boltz-2, an open biomolecular structure predictor. Boltz is an agent skill from adaptyvbio/protein-design-skills. Structure prediction using Boltz-1/Boltz-2, an open biomolecular structure predictor.

When should I use Boltz?

Boltz fits situations like: predicting protein complex structures; validating designed binders; need open-source alternative to AF2; predicting protein-ligand complexes.

How do I install Boltz in Claude Code?

Run `npx skills add adaptyvbio/protein-design-skills --skill boltz -a claude-code`. Or copy the skill folder (skills/boltz in adaptyvbio/protein-design-skills) into .claude/skills/boltz in your project. Claude Code loads it when a task matches its description.

How do I install Boltz in Codex?

Run `npx skills add adaptyvbio/protein-design-skills --skill boltz -a codex`. Or copy the skill folder (skills/boltz in adaptyvbio/protein-design-skills) into .agents/skills/boltz in your project. Codex loads it when a task matches its description.

Can I use Boltz in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add adaptyvbio/protein-design-skills --skill boltz -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/boltz, .gemini/skills/boltz, .github/skills/boltz and .opencode/skills/boltz in your project.

What does Boltz need to run?

Going by SKILL.md and its folder, Boltz needs the command-line tools its instructions call (modal and pip). Our summary lists: Python 3.

Does Boltz access the network?

SKILL.md contains no URLs. Its commands use pip, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Boltz safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Boltz use?

Boltz is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Boltz use?

About 1.3k tokens (SKILL.md is roughly 5.1k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Boltz?

Skills that share tags, products or a category with Boltz: Alphafold Database Fetch And Analyze (google-deepmind/science-skills, 3.2k stars), Biopipelines (locbp-uzh/biopipelines, 109 stars), Bio DB Tools (DrugClaw/DrugClaw, 125 stars) and Gget (davila7/claude-code-templates, 32k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Boltz?

adaptyvbio (a GitHub organization) maintains it in adaptyvbio/protein-design-skills, which has 163 GitHub stars. The repository holds 24 skills in this directory. The repository was last updated on June 11, 2026.

Source: adaptyvbio/protein-design-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.