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

# Errors

> Handle nono-go sentinel errors and detailed FFI error messages

Failing operations return `*nono.Error`. Use `errors.Is` with the exported
sentinel errors when you need to branch on the failure kind.

```go theme={null}
err := caps.AllowPath("/missing", nono.AccessRead)
if errors.Is(err, nono.ErrPathNotFound) {
	log.Println("path does not exist")
}
```

Use `errors.As` when you need the numeric code or human-readable message from
the native library.

```go theme={null}
var nonoErr *nono.Error
if errors.As(err, &nonoErr) {
	log.Println(nonoErr.Code(), nonoErr.Message())
}
```

## Sentinel errors

| Sentinel                       | Meaning                                    |
| ------------------------------ | ------------------------------------------ |
| `nono.ErrPathNotFound`         | The path does not exist                    |
| `nono.ErrExpectedDirectory`    | A directory was required                   |
| `nono.ErrExpectedFile`         | A file was required                        |
| `nono.ErrPathCanonicalization` | Path canonicalization failed               |
| `nono.ErrNoCapabilities`       | No capabilities were configured            |
| `nono.ErrSandboxInit`          | Platform sandbox initialization failed     |
| `nono.ErrUnsupportedPlatform`  | Sandboxing is unavailable on this platform |
| `nono.ErrBlockedCommand`       | A command was blocked by policy            |
| `nono.ErrConfigParse`          | Configuration parsing failed               |
| `nono.ErrProfileParse`         | Profile parsing failed                     |
| `nono.ErrIO`                   | An I/O operation failed                    |
| `nono.ErrInvalidArg`           | An invalid argument was passed             |
| `nono.ErrTrustVerification`    | Trust verification failed                  |
| `nono.ErrUnknown`              | Unknown or uncategorized failure           |

`nono.Error.Is` matches by error code, so the native message does not need to
match the sentinel's message.