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

# Error Handling & Fallback

> How Planck AI Gateway handles errors and automatically falls back between billing methods

Planck AI Gateway automatically tries multiple billing methods to ensure your requests succeed. When one method fails, it falls back to alternatives and returns the most actionable error to help you fix issues quickly.

## How Fallback Works

The AI Gateway supports two billing methods:

<CardGroup cols={2}>
  <Card title="Pass-Through Billing (PTB)" icon="credit-card">
    Pay-as-you-go with Planck credits. Simple, no provider account needed.
  </Card>

  <Card title="Bring Your Own Keys (BYOK)" icon="key">
    Use your own provider API keys. You're billed directly by the provider.
  </Card>
</CardGroup>

**Automatic Fallback**: When you configure both methods, the gateway tries BYOK first. If your provider key cannot serve the request, the gateway can fall back to PTB when credits and a managed provider route are available.

***

## Error Priority Logic

When both billing methods fail, the gateway returns the **most actionable error** to help you resolve the issue:

### Priority Order

1. **403 Forbidden** → Critical access issue, contact support
2. **401 Unauthorized** → Fix your provider API key
3. **400 Bad Request** → Fix your request format
4. **500 Server Error** → Provider issue or configuration problem
5. **429 Rate Limit** → Only shown if all attempts hit rate limits

<Note>
  **Why this order?** If you configured BYOK, errors from your provider keys (401, 500) are more actionable than PTB's "insufficient credits" (429). You chose BYOK for a reason!
</Note>

***

## Common Error Scenarios

| Error Code | What It Means           | Action Required                                             | Example                         |
| ---------- | ----------------------- | ----------------------------------------------------------- | ------------------------------- |
| **401**    | Authentication failed   | Check your provider API key in settings                     | Invalid OpenAI API key          |
| **403**    | Access forbidden        | Contact [support@inquantum.ai](mailto:support@inquantum.ai) | Wallet suspended, model blocked |
| **400**    | Invalid request format  | Fix your request body or parameters                         | Missing required field          |
| **429**    | Insufficient credits    | Add credits OR configure provider keys                      | No Planck credits, no BYOK      |
| **500**    | Upstream provider error | Check provider status or retry                              | Provider API timeout            |
| **503**    | Service unavailable     | Provider temporarily down, retry later                      | Provider maintenance            |

***

## Fallback Scenarios

<AccordionGroup>
  <Accordion title="Scenario 1: BYOK Succeeds">
    **Setup**: You have a valid provider key configured or provided

    **Result**: ✅ Request completes using Bring Your Own Keys

    **Error**: None - successful response
  </Accordion>

  <Accordion title="Scenario 2: BYOK Fails, PTB Succeeds">
    **Setup**: Your provider key fails, but you have Planck credits and a managed route is available

    **Result**: ✅ Request completes using Pass-Through Billing

    **Error**: None - successful response
  </Accordion>

  <Accordion title="Scenario 3: BYOK Fails, PTB Fails">
    **Setup**: Your provider key fails and PTB is unavailable or also fails

    **Result**: ❌ Request fails

    **Error Returned**: The most actionable error from the failed attempts

    **Why**: If your provider key is invalid, that error is usually more actionable than a generic fallback failure.

    **Example**:

    ```json theme={null}
    {
      "error": {
        "message": "Authentication failed",
        "type": "invalid_api_key",
        "code": 401
      }
    }
    ```
  </Accordion>

  <Accordion title="Scenario 4: No BYOK Configured, PTB Fails">
    **Setup**: No Planck credits and no provider keys configured

    **Result**: ❌ Request fails

    **Error Returned**: 429 Insufficient credits

    **Why**: No alternative billing method available

    **Example**:

    ```json theme={null}
    {
      "error": {
        "message": "Insufficient credits",
        "type": "request_failed",
        "code": 429
      }
    }
    ```

    **Solutions**:

    1. [Add Planck credits](https://us.inquantum.ai/credits)
    2. [Configure provider keys](https://us.inquantum.ai/settings/providers)
    3. Enable [automatic retries](/planck-headers/header-directory#retries) with `Planck-Retry-Enabled: true` to handle transient failures

    <Info>
      **Retries can help!** If you're experiencing temporary rate limits or server errors, use [Planck retry headers](/planck-headers/header-directory#retries) to automatically retry failed requests with exponential backoff.
    </Info>
  </Accordion>
</AccordionGroup>

***

## Understanding Error Sources

When you see an error, you can determine which billing method it came from:

**PTB Errors**:

* 429: "Insufficient credits" → [Add credits](https://us.inquantum.ai/credits)
* 403: "Wallet suspended" → Contact support

**BYOK Errors**:

* 401: "Invalid API key" → [Check provider keys](https://us.inquantum.ai/settings/providers)
* 500: "Provider error" → Check provider status
* 503: "Service unavailable" → Provider having issues

***

## Best Practices

<CardGroup cols={2}>
  <Card title="Configure Both Methods" icon="shield-check">
    Set up both PTB and BYOK for maximum reliability. If one fails, the other serves as backup.
  </Card>

  <Card title="Monitor Credit Balance" icon="chart-line">
    Keep track of your Planck credits to avoid 429 errors during critical requests.
  </Card>

  <Card title="Enable Automatic Retries" icon="rotate-cw">
    Use [Planck retry headers](/planck-headers/header-directory#retries) to automatically retry transient errors (429, 500, 503) with exponential backoff.
  </Card>

  <Card title="Log Error Details" icon="file-text">
    Log the full error response to debug provider-specific issues quickly.
  </Card>
</CardGroup>

***

## Error Handling in Code

<Tip>
  **Prefer built-in retries**: Instead of implementing your own retry logic, use [Planck's automatic retry headers](/planck-headers/header-directory#retries) by adding `Planck-Retry-Enabled: true` to your requests. This handles exponential backoff automatically.
</Tip>

### Retry Logic Example

```typescript theme={null}
import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://api.inquantum.ai",
  apiKey: process.env.PLANCK_API_KEY,
});

async function callWithRetry(maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      const response = await client.chat.completions.create({
        model: "gpt-4o-mini",
        messages: [{ role: "user", content: "Hello!" }],
      });
      return response;
    } catch (error: any) {
      const status = error?.status || 500;

      // Don't retry auth errors or bad requests
      if (status === 401 || status === 403 || status === 400) {
        throw error;
      }

      // Don't retry insufficient credits unless it's the last attempt
      if (status === 429 && i === maxRetries - 1) {
        throw error;
      }

      // Retry transient errors (500, 503) with exponential backoff
      if (status >= 500 || status === 429) {
        await new Promise(resolve => setTimeout(resolve, Math.pow(2, i) * 1000));
        continue;
      }

      throw error;
    }
  }
}
```

### Error Classification

```typescript theme={null}
function classifyError(error: any) {
  const status = error?.status || 500;

  if (status === 401) {
    return {
      type: "authentication",
      action: "Check your API keys in settings",
      retryable: false
    };
  }

  if (status === 429) {
    return {
      type: "rate_limit",
      action: "Add credits or wait before retrying",
      retryable: true
    };
  }

  if (status >= 500) {
    return {
      type: "server_error",
      action: "Retry with exponential backoff",
      retryable: true
    };
  }

  return {
    type: "unknown",
    action: "Check error message for details",
    retryable: false
  };
}
```

***

## Related Resources

* [Automatic Retries](/planck-headers/header-directory#retries) - Configure retry headers for handling transient failures
* [Provider Routing](/gateway/provider-routing) - Learn how to configure fallback providers
* [Settings: Provider Keys](https://us.inquantum.ai/settings/providers) - Add your provider API keys
* [Credits](https://us.inquantum.ai/credits) - Add Planck credits for Pass-Through Billing

<Info>
  **Need Help?** If you're seeing unexpected errors or need assistance configuring fallback, contact us at [support@inquantum.ai](mailto:support@inquantum.ai).
</Info>