# `once cache blob exists`

Check whether a blob exists. Exits 0 on hit, 1 on miss; with `--format json|toon`, always exits 0 and reports `present` in the structured output.

## Synopsis

```text
once cache blob exists <DIGEST>
```

## Arguments

| Argument | Required | Description |
| --- | --- | --- |
| `<DIGEST>` | yes | Blob digest to probe. |