Error Handling & Fallback - Helicone OSS LLM Observability

Helicone 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:

Pass-Through Billing (PTB)

Pay-as-you-go with Helicone credits. Simple, no provider account needed.

Bring Your Own Keys (BYOK)

Use your own provider API keys. You're billed directly by the provider.

Automatic Fallback: When you configure both methods, the gateway tries PTB first. If it fails (e.g., insufficient credits), it automatically falls back to BYOK.

Error Priority Logic#

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

Priority Order#

403 Forbidden → Critical access issue, contact support
401 Unauthorized → Fix your provider API key
400 Bad Request → Fix your request format
500 Server Error → Provider issue or configuration problem
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!

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@helicone.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 Helicone 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#

Scenario 1: PTB Succeeds

Setup: You have Helicone credits

Result: ✅ Request completes using Pass-Through Billing

Error: None - successful response

Scenario 2: PTB Fails, BYOK Succeeds

Setup: No Helicone credits, but valid provider API key configured

Result: ✅ Request completes using your provider key

Error: None - successful response (PTB's 429 is hidden since BYOK succeeded)

Scenario 3: PTB Fails, BYOK Fails

Setup: No Helicone credits, invalid/failing provider key

Result: ❌ Request fails

Error Returned: BYOK's error (401, 500, etc.) - NOT PTB's 429

Why: You configured BYOK, so we show what's wrong with your provider key rather than "insufficient credits"

Example:

{  "error": {    "message": "Authentication failed",    "type": "invalid_api_key",    "code": 401  }}

Scenario 4: No BYOK Configured, PTB Fails

Setup: No Helicone credits, no provider keys configured

Result: ❌ Request fails

Error Returned: 429 Insufficient credits

Why: No alternative billing method available

Example:

{  "error": {    "message": "Insufficient credits",    "type": "request_failed",    "code": 429  }}

Solutions:

Add Helicone credits at /credits
Configure provider keys in /settings/providers
Enable automatic retries with Helicone-Retry-Enabled: true to handle transient failures

Info

Retries can help! If you're experiencing temporary rate limits or server errors, use Helicone retry headers to automatically retry failed requests with exponential backoff.

Understanding Error Sources#

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

PTB Errors:

429: "Insufficient credits" → Add credits at /credits
403: "Wallet suspended" → Contact support

BYOK Errors:

401: "Invalid API key" → Check provider keys in /settings/providers
500: "Provider error" → Check provider status
503: "Service unavailable" → Provider having issues

Best Practices#

Configure Both Methods

Set up both PTB and BYOK for maximum reliability. If one fails, the other serves as backup.

Monitor Credit Balance

Keep track of your Helicone credits to avoid 429 errors during critical requests.

Enable Automatic Retries

Use Helicone retry headers to automatically retry transient errors (429, 500, 503) with exponential backoff.

Log Error Details

Log the full error response to debug provider-specific issues quickly.

Error Handling in Code#

Tip

Prefer built-in retries: Instead of implementing your own retry logic, use Helicone's automatic retry headers by adding Helicone-Retry-Enabled: true to your requests. This handles exponential backoff automatically.

Retry Logic Example#

import OpenAI from "openai";const client = new OpenAI({  baseURL: "https://ai-gateway.helicone.ai",  apiKey: process.env.HELICONE_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#

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  };}

Automatic Retries - Configure retry headers for handling transient failures
Provider Routing - Learn how to configure fallback providers
Settings: Provider Keys - Add your provider API keys
Credits - Add Helicone credits for Pass-Through Billing

Info

Need Help? If you're seeing unexpected errors or need assistance configuring fallback, contact us at support@helicone.ai or join our Discord community.

How Fallback Works#

Error Priority Logic#

Priority Order#

Common Error Scenarios#

Fallback Scenarios#

Understanding Error Sources#

Best Practices#

Error Handling in Code#

Retry Logic Example#

Error Classification#

Related Resources#