Overview

v0 is considered deprecated and will be fully removed in a future release.

Verifiers is our library for creating environments to train and evaluate LLMs. Environments contain everything required to run and evaluate a model on a particular task:

A dataset of task inputs
A harness for the model (tools, sandboxes, context management, etc.)
A reward function or rubric to score the model’s performance

Environments can be used for training models with reinforcement learning (RL), evaluating capabilities, generating synthetic data, experimenting with agent harnesses, and more. Verifiers is tightly integrated with the Environments Hub, as well as our training framework prime-rl and our Hosted Training platform.

Getting Started

Ensure you have uv installed, as well as the prime CLI tool:

# install uv
curl -LsSf https://astral.sh/uv/install.sh | sh
# install the prime CLI
uv tool install prime
# log in to the Prime Intellect platform
prime login

To set up a new workspace for developing environments, do:

# ~/dev/my-lab
prime lab setup 

This sets up a Python project if needed (with uv init), installs verifiers (with uv add verifiers), creates the recommended workspace structure, and downloads useful starter files:

configs/
├── endpoints.toml      # OpenAI-compatible API endpoint configuration
├── rl/                 # Example configs for Hosted Training
├── eval/               # Example multi-environment eval configs
└── gepa/               # Example configs for prompt optimization
.prime/
└── skills/             # Bundled workflow skills for create/browse/review/eval/GEPA/train/brainstorm
environments/
└── AGENTS.md           # Documentation for AI coding agents
AGENTS.md               # Top-level documentation for AI coding agents
CLAUDE.md               # Claude-specific pointer to AGENTS.md

Alternatively, add verifiers to an existing project:

uv add verifiers && prime lab setup --skip-install

Optional features are installed with extras:

Extra	Install	Enables
`modal`	`uv add "verifiers[modal]"`	The v1 Modal sandbox runtime
`notebook`	`uv add "verifiers[notebook]"`	`Environment.generate_sync()` inside Jupyter or another active event loop

Environments built with Verifiers are self-contained Python modules. To initialize a fresh environment template, do:

uv run vf-init my-env # creates a v0 stub in ./environments/my_env

This will create a new module called my_env with a runnable environment template.

environments/my_env/
├── my_env.py           # Main implementation
├── pyproject.toml      # Dependencies and metadata
└── README.md           # Documentation

Environment modules should expose a load_environment function which returns an environment object. For simple legacy environments, this can still be a direct constructor:

# my_env.py
import verifiers as vf


def load_environment(dataset_name: str = "gsm8k") -> vf.Environment:
    dataset = vf.load_example_dataset(dataset_name)  # 'question'

    async def correct_answer(completion, answer) -> float:
        completion_ans = completion[-1]["content"]
        return 1.0 if completion_ans == answer else 0.0

    rubric = vf.Rubric(funcs=[correct_answer])
    env = vf.SingleTurnEnv(dataset=dataset, rubric=rubric)
    return env

To run a local evaluation with any OpenAI-compatible model, install the environment into your project and run it with vf-eval:

prime env install my-env # installs ./environments/my_env into the project
uv run vf-eval my-env -m openai/gpt-5-nano -s # run and save eval results locally

Evaluations use Prime Inference by default; configure your own API endpoints in ./configs/endpoints.toml. Saved results land under outputs/evals/<env>--<model>/<run-id>/ (metadata.json and results.jsonl). To view a run on the dashboard, upload it. Uploads need the environment on the Environments Hub: push it with prime env push if you haven’t, then pass its slug with --env:

prime eval push outputs/evals/my-env--openai--gpt-5-nano/<run-id> --env <owner>/my-env

To publish the environment to the Environments Hub, do:

prime env push my-env # equivalent to --path ./environments/my_env

To evaluate an environment from the Environments Hub, install it first, then run it:

prime env install primeintellect/math-python
uv run vf-eval primeintellect/math-python

Documentation

Environments — Create datasets, rubrics, and custom multi-turn interaction protocols. Evaluation - Evaluate models using your environments. Training — Train models in your environments with reinforcement learning. Development — Contributing to verifiers API Reference — Understanding the API and data structures FAQs - Other frequently asked questions.

Getting Started

Lab

Inference

Model Factory

Libraries

Compute

Getting Started

Documentation

​Getting Started

​Documentation

Getting Started

Documentation