# Cast Configuration

The `cast` section of `atmos.yaml` configures how Atmos records terminal sessions as asciicast files. Use `cast.recording` to record every command automatically, and `cast.session` to control how the shell starts in session-mode recordings.

## Configuration

**File:** `atmos.yaml`

```yaml
cast:
  recording:
    enabled: false
    base_path: "./casts"
    input: false
    width: 120
    height: 36
  session:
    shell_init: clean
```

## Recording

- **`cast.recording.enabled`** — Record every Atmos command automatically. Automatic recording skips `--help` and shell-completion invocations. An explicit `--cast` flag or `ATMOS_CAST` always records, including help output.
- **`cast.recording.base_path`** — Directory under which automatic and intermediate casts are written.
- **`cast.recording.input`** — Also record stdin keystrokes, not just output.
- **`cast.recording.width`, `cast.recording.height`** — Terminal dimensions in columns and rows for the recording. Environment variables `ATMOS_CAST_RECORDING_WIDTH` and `ATMOS_CAST_RECORDING_HEIGHT` override them.

## Session

- **`cast.session.shell_init`** — Default startup behavior for the shell in `mode: session` casts, including those produced from VHS tapes. Environment variable: `ATMOS_CAST_SESSION_SHELL_INIT`.
  - `clean` (default) starts the shell without the user's startup files, so recordings are reproducible and do not leak personal prompts, aliases, or plugins.
  - `user` loads the shell's normal startup files.
  - Any other value is a path to an rc file that is sourced instead.
  Precedence, highest first: the cast step's [`shell_init`](/steps/type/cast#fields), the `--shell-init` flag of [`atmos cast record`](/cli/commands/cast/record), this setting, then `clean`.

## Related

- [`type: cast` step](/steps/type/cast)
- [`atmos cast record`](/cli/commands/cast/record)
- [Global flag `--cast`](/cli/global-flags)