HUD Documentation - Evaluations and RL Environments.

Fastest path - hand the docs to your coding agent first. The HUD docs skill scaffolds correct v6 environments and flags weak task designs as you build:

npx skills add https://docs.hud.ai

The rest of this page walks the setup path by hand.

1. Install

uv tool install hud --python 3.12

pip install hud

2. Set your API key

Get a key from hud.ai/project/api-keys - one key both routes models through the HUD gateway and traces every rollout.

hud set HUD_API_KEY=your-key-here

3. Create a Test Environment

hud init my-env normally starts from the coding environment. This five-minute walkthrough uses the minimal example so every part fits on one page:

hud init my-env --template blank
cd my-env

This includes a ready-to-run task in tasks.py:

tasks.py

from hud import Environment

env = Environment(name="letter-count")

@env.template()
async def count_letter(word: str = "strawberry", letter: str = "r"):
    answer = yield f"How many '{letter}'s are in '{word}'? Reply with just the number."
    yield 1.0 if answer and str(word.count(letter)) in answer else 0.0

tasks = [count_letter(word=w) for w in ("strawberry", "raspberry", "blueberry")]

4. Run it

hud eval tasks.py claude

hud eval spawns the environment locally, runs the claude agent, and grades it. Every rollout generates a replayable trace on hud.ai.

5. View your traces

hud eval prints a job link. Open it on hud.ai to replay each trace step by step - every prompt, action, and the reward the grader returned. From the platform you can run whole tasksets across models and compare the results.

Start here

Guides

Reference

Advanced

Experimental

Cookbooks

Internals

More

Quickstart

1. Install

2. Set your API key

3. Create a Test Environment

4. Run it

5. View your traces

​1. Install

​2. Set your API key

​3. Create a Test Environment

​4. Run it

​5. View your traces

1. Install

2. Set your API key

3. Create a Test Environment

4. Run it

5. View your traces