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

# Environments

> The compute shape of your agent VMs — machine type, disk type, disk size, and cloud substrate that determine performance and per-hour cost.

An environment defines how big your agent VMs are — the machine type (vCPUs, memory) and disk size. Each [workspace](/concepts/workspaces) references one environment via its `environment_ref` field.

Environments are cloud-aware but location-independent. An environment targets a substrate (`GCP` or `AWS`), which determines what machine types are valid. But it does not specify *where* to run — that's the [placement's](/concepts/placement) job. You can reuse the same environment across any [placement](/concepts/placement) of the same substrate.

## Machine types

Machine types are platform-provided resources that name a specific VM size — vCPUs, memory, architecture, and optional GPU. Environments reference them by name. List available machine types with [`murmur get machine-type`](/cli/get).

You do not create machine types — they are builtins. You pick one when defining an environment.

## Creating an environment

Create environments with [`murmur set environment`](/cli/set). Each environment specifies a substrate, machine type reference, disk type reference, and optional disk size. Then reference it from a [workspace](/concepts/workspaces) via the `environment_ref` field. See the [environment reference](/catalog/environment) for all fields.

***

| Type      | Page                                            |
| --------- | ----------------------------------------------- |
| Reference | [environment](/catalog/environment)             |
| Reference | [machine-type](/catalog/machine-type)           |
| Reference | [disk-type](/catalog/disk-type)                 |
| Guide     | [VM environment](/configuration/vm-environment) |
| Concept   | [Placements](/concepts/placement)               |
| Concept   | [Workspaces](/concepts/workspaces)              |