# Version

The `version` section configures how Atmos handles version management, including automatic update checking and version constraint enforcement to ensure consistent behavior across teams and environments.

## Configuration

**File:** `atmos.yaml`

```yaml
version:
  # Pin project to a specific Atmos version
  use: "1.199.0"

  # Automatic update checking
  check:
    enabled: true
    frequency: daily

  # Version constraint enforcement
  constraint:
    require: ">=1.100.0"
    enforcement: fatal
    message: "Please upgrade Atmos to use this configuration."
```

## Version Sections

| Section | Description |
|---------|-------------|
| [Use](/cli/configuration/version/use) | Pin project to a specific Atmos version |
| [Check](/cli/configuration/version/check) | Automatic version checking and update notifications |
| [Constraint](/cli/configuration/version/constraint) | Enforce Atmos version requirements for your configuration |

## Environment Variables

- **`ATMOS_USE_VERSION`**
  Specify which version of Atmos to use. Env var equivalent of 
  `--use-version`
   flag.
- **`ATMOS_VERSION_USE`**
  Internal env var set by the 
  `--use-version`
   flag. Highest precedence in version resolution.
- **`ATMOS_VERSION`**
  Convenience alias matching 
  `tfenv`
  /
  `goenv`
   conventions. Lower precedence than 
  `ATMOS_VERSION_USE`
  .
- **`ATMOS_VERSION_CHECK_ENABLED`**
  Enable or disable automatic version checking.
- **`ATMOS_VERSION_ENFORCEMENT`**
  Override version constraint enforcement level: 
  `fatal`
  , 
  `warn`
  , or 
  `silent`
  .

## See Also

- [CLI Configuration](/cli/configuration) — Overview of CLI configuration
- [`atmos version`](/cli/commands/version/usage) — Display version and check for updates
- [Atmos Version Management](/howto/atmos-version-management) — How-to guide with profiles