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

# Errors

> Retry and recovery for polling, private reads, hosted flows, and failed checks.

## When things fail

| Class        | Fix                            |
| ------------ | ------------------------------ |
| Validation   | Fix request shape              |
| Interactive  | Hosted `/verify` or VerifyGate |
| Async        | Poll with backoff              |
| Private read | Owner auth, retry              |
| Transient    | Backoff; `Retry-After`         |

## Error classes

All SDK errors extend `SDKError` and carry a `.code` and `.details`. Import them from `@neus/sdk`:

| Class                 | `isRetryable`       | Use it for                                                                              |
| --------------------- | ------------------- | --------------------------------------------------------------------------------------- |
| `ApiError`            | `true` on 5xx / 429 | HTTP failures — also has `.statusCode`, `.isClientError`, `.isServerError`, `.response` |
| `ValidationError`     | `false`             | Bad request shape — has `.field`, `.value`                                              |
| `NetworkError`        | `true`              | Transport / DNS / timeout                                                               |
| `ConfigurationError`  | `false`             | Missing/invalid client config — has `.configKey`                                        |
| `VerificationError`   | `true`              | Verifier failure — has `.verifierId`                                                    |
| `AuthenticationError` | `false`             | Owner/session/key not allowed                                                           |

```javascript theme={"dark"}
import { ApiError } from '@neus/sdk';

try {
  await client.gateCheck({ gateId: 'gate_your-app-name', address });
} catch (error) {
  if (error instanceof ApiError && error.isRetryable) {
    // back off and retry (5xx / 429)
  } else if (error.code === 'VALIDATION_ERROR') {
    // fix the request and do not retry
  }
}
```

## Polling Example

```javascript theme={"dark"}
const final = await client.pollProofStatus(qHash, {
  interval: 3000,
  timeout: 60000
});
```

## Private Proof Read Example

```javascript theme={"dark"}
const privateData = await client.getPrivateProof(qHash, window.ethereum);
```

* Don’t loop-create on ambiguous errors - keep stored qHashes for resume.
* Say when a hosted step is required - avoid generic “error” only.