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

# Environments

> How jnc manages environments and features within a workspace.

# Environments

A jnc workspace can contain multiple **environments**, each composed of one or more **features**. This system lets you maintain separate dependency sets for different purposes (development, testing, production) within a single workspace.

## Default environment

Every workspace has a `default` environment that includes the `default` feature. When you run `jnc add python`, the package is added to the default feature and is available in the default environment.

```toml theme={null}
[dependencies]
python = ">=3.12,<4"
numpy = ">=2.0,<3"
```

## Features

A **feature** is a named set of dependencies, tasks, and configuration. Features are the building blocks of environments.

```toml theme={null}
[feature.test.dependencies]
pytest = ">=8.0,<9"

[feature.docs.dependencies]
sphinx = ">=7.0,<8"
```

Add packages to a feature:

```bash theme={null}
jnc add --feature test pytest
jnc add --feature docs sphinx
```

## Composing environments

Environments are composed by combining features. Define them in the manifest:

```toml theme={null}
[environments]
test = ["default", "test"]
docs = ["default", "docs"]
```

The `test` environment includes everything from both `default` and `test` features.

## Using environments

Target a specific environment with most commands:

```bash theme={null}
jnc run --environment test pytest
jnc shell --environment docs
jnc list --environment test
jnc install --environment test
```

## Environment installation

When you run `jnc install`, all environments are solved and installed. Each environment gets its own isolated set of packages. Packages shared across environments are deduplicated on disk using hard links or reflinks.

## Platform support

Each environment inherits the workspace's target platforms. You can also specify platform-specific dependencies within features:

```toml theme={null}
[target.linux-aarch64.dependencies]
cuda-toolkit = ">=12.0,<13"

[feature.gpu.target.linux-aarch64.dependencies]
pytorch-cuda = ">=2.0,<3"
```