> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hud.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Concepts

> The objects HUD is built around and how they relate.

Every page in these docs uses the same vocabulary. Read this page once; the rest of the platform is
these objects and the actions on them.

## Objects

| Concept | What it is |
| - | - |
| **Team** | Your organization on HUD. It owns every resource, credential, file, and credit balance. |
| **Project** | A workspace inside a team that groups resources and scopes who can see and change them. Every team has a Main project. See [Projects](/platform/projects). |
| **Environment** | A containerized world an agent acts in: a workspace with files and a shell, a browser, a desktop, a robot simulator, or any service with tools. See [Environments](/platform/environments). |
| **Build** | One deployed version of an environment's source and image. Builds are immutable. |
| **Task template** | A parameterized task definition that an environment exposes, such as `review_files(prompt, attachments, criteria)`. The SDK calls it a scenario. |
| **Task** | One template with its arguments filled in: what the agent is asked, what it works with, and how it is graded. |
| **Task version** | An immutable snapshot of a task. Editing a task creates a new version; a trace keeps the version it ran. |
| **Taskset** | A named collection of tasks: a benchmark, a training set, or a queue of work for task authors. See [Tasksets](/platform/tasksets). |
| **Evaluation job** | One run of a set of tasks across models, with a number of repetitions. See [Evaluations](/platform/evaluations). |
| **Trace** | One attempt by one model at one task: every step, tool call, observation, and the final reward. See [Traces](/platform/traces). |
| **Reward** | The grader's score for a trace, from 0 to 1. |
| **QA result** | A QA agent's verdict on a trace or a task, with findings. See [QA agents](/platform/qa-agents). |
| **Model** | An entry in the model catalog: a provider model, or a trainable model your team owns. See [Models](/platform/models). |
| **Checkpoint** | A saved set of weights for a trainable model. |
| **Data file** | A file uploaded to the team's store that tasks can attach as input. See [Data](/platform/data). |

## Environments and tasks

An environment decides **how** work happens and is graded: the tools the agent gets and the grading
logic. A task decides **what** is asked by filling in a template's arguments, and each template
defines its own: `review_files` asks for a prompt, files, and a rubric, while the robot gripper's
`pick-object` asks for a scene, an object, and a lift height. One environment serves many tasks, so
people who never write code can create tasks by filling in a template's form. See
[create tasks in the web app](/platform/create-tasks).

## Versions and reproducibility

Nothing a trace depends on changes under it:

* A trace records the task version and the environment build it ran.
* Editing a task creates a new version. Earlier traces keep pointing at the version they ran.
* A new build does not alter earlier builds. Runs started during a build keep the previous successful
  build until the new one is ready.

Because of this, jobs that run the same taskset stay comparable, and any trace can be explained
from the exact inputs it saw.

## Task status

Each task version moves through a review lifecycle: it is **Pending** while authors work on it,
**Ready** when an author submits it, and then **Verified**, **Revision**, or **Rejected** after a
reviewer decides. Tasksets can add custom stages before Ready. See
[task lifecycle and review](/platform/task-lifecycle).

## Who can do what

Access works at three levels:

| Level | Who it covers | Controls |
| - | - | - |
| **Team role** | Every member: Admin, Member, or External. | Settings, billing, members, and default visibility. See [roles](/platform/team#roles). |
| **Project scope** | A member or a whole team in one project: Contributor, View, Create, Review, or Manage. | What they can see, create, review, and administer in that project. See [Projects](/platform/projects). |
| **Taskset scope** | A member or team on one taskset: View, Create, or Review. | Work on a single taskset without wider project access. See [Tasksets](/platform/tasksets#share-a-taskset). |

An API key acts as the member it belongs to, in that member's team. See
[API keys and secrets](/platform/credentials).


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