routstr-core/docs/api/errors.md

Error Handling

This guide covers error responses, codes, and handling strategies for the Routstr API.

Error Response Format

Versioned endpoints use a structured JSON error object:

{
  "error": {
    "type": "error_type",
    "message": "Human-readable error message",
    "code": "error_code",
    "details": {
      "additional": "context-specific information"
    }
  }
}

Lightning invoice errors

The /v2/lightning/* endpoints use the structured error object above. In the HTTP response, error is available at the top level and mirrored under detail.error. Clients should branch on error.code.

Endpoint case	Status	type	code
Top-up without a credential	401	invalid_request_error	topup_authorization_required
Top-up with a non-sk- credential	400	invalid_request_error	topup_invalid_api_key_format
Top-up target key not found	404	invalid_request_error	topup_api_key_not_found
Invoice not found during status or recovery	404	invalid_request_error	invoice_not_found
Cashu mint rate-limited	503	mint_rate_limited	lightning_mint_rate_limited
Cashu mint unreachable	503	mint_unreachable	lightning_mint_unreachable
Unexpected invoice creation failure	500	api_error	invoice_creation_failed

Request validation failures, including non-positive or excessive amounts, use FastAPI's standard 422 validation response. Only the 503 mint failures are retryable. Use backoff and honor the Retry-After header when present. The compatibility endpoints /lightning/* and /v1/balance/lightning/* retain their original string detail errors and legacy status behavior.

HTTP Status Codes

Status	Meaning	Common Causes
400	Bad Request	Invalid parameters, malformed JSON
401	Unauthorized	Invalid or missing API key
402	Payment Required	Insufficient balance
403	Forbidden	Access denied to resource
404	Not Found	Endpoint or resource doesn't exist
422	Unprocessable Entity	Validation errors
424	Failed Dependency	An upstream inference provider failed. This node is healthy — see Upstream attribution
429	Too Many Requests	Rate limit exceeded (this node or an upstream provider)
500	Internal Server Error	Server-side error on this node
502	Bad Gateway	Gateway-level failure
503	Service Unavailable	Temporary outage

Upstream attribution (424 Failed Dependency)

When an upstream provider fails, this node is still healthy, so the failure is reported as a non-5xx status. Clients should not mark the node down for it.

An upstream-attributable failure answers:

• Status: 424
• error.code: UPSTREAM_UNAVAILABLE
• Header: X-Routstr-Error-Scope: upstream
• error.upstream_status: the provider's own status (e.g. 503). Failures built by the payment helpers carry it in error.details.upstream_status instead

HTTP/1.1 424 Failed Dependency
X-Routstr-Error-Scope: upstream
Content-Type: application/json

{
  "error": {
    "type": "upstream_error",
    "message": "Service Unavailable",
    "code": "UPSTREAM_UNAVAILABLE",
    "upstream_status": 503
  }
}

Two exceptions keep their own status:

• Rate limits answer 429 with error.code = UPSTREAM_RATE_LIMIT, even when the provider wrapped them in a 5xx.
• Provider-side 4xx (400/401/403/404/422) passes through unchanged.

Node faults (unreachable mint, database failure, internal exception) still answer 500 with no X-Routstr-Error-Scope header.

Error Types

Authentication Errors

Invalid API Key (malformed credential)

Returned when the Authorization value is neither an sk-... API key nor a cashu... token.

{
  "error": {
    "type": "invalid_request_error",
    "message": "Invalid API key format. Expected an 'sk-...' API key or a 'cashu...' token.",
    "code": "invalid_api_key"
  }
}

Status: 401
Resolution: Send a well-formed credential. The node logs the received preview and length (Invalid API key format: preview=… length=…) to distinguish a typo from a wrong-shaped header.

API Key Not Found (sk- key unknown to this node)

Returned when the credential starts with sk- and this node has no record of it — for example a key minted by a different Routstr node, or one removed by key pruning. This is not a formatting problem.

{
  "error": {
    "type": "invalid_request_error",
    "message": "Key not found. Deposit first via /v1/wallet/create to get a key on this node.",
    "code": "key_not_found"
  }
}

Status: 401
Resolution: Create or fund a key on this node via POST /v1/wallet/create. Keys are node-local; an sk- key issued by another node is not accepted here.

Expired API Key

{
  "error": {
    "type": "authentication_failed",
    "message": "API key has expired",
    "code": "key_expired",
    "details": {
      "expired_at": "2024-01-01T00:00:00Z",
      "refund_available": true
    }
  }
}

Status: 401
Resolution: Create new API key or contact admin for refund

Missing Authorization

{
  "error": {
    "type": "authentication_failed",
    "message": "Authorization header required",
    "code": "missing_auth"
  }
}

Status: 401
Resolution: Include Authorization: Bearer {api_key} header

Payment Errors

Insufficient Balance

{
  "error": {
    "type": "insufficient_balance",
    "message": "Insufficient balance for request",
    "code": "payment_required",
    "details": {
      "balance": 100,
      "required": 154,
      "shortfall": 54,
      "estimated_tokens": {
        "prompt": 50,
        "completion": 150
      }
    }
  }
}

Status: 402
Resolution: Top up API key balance

Cashu Token Redemption Errors

These errors are returned when a Cashu token you pay with cannot be redeemed. They apply to every endpoint that accepts a token:

• Per-request payment via the X-Cashu header (chat completions + Responses API).
• API key top-up via POST /v1/wallet/topup.
• Minting an API key from a token sent in Authorization: Bearer <cashu-token>.

All three share one classifier, so the same failure yields the same HTTP status and sanitized message everywhere. All three paths also expose the same structured type and code — branch on type (or code for finer granularity) on any of them.

type	Status	code	Retryable	Meaning
token_already_spent	400	cashu_token_already_spent	No	The token was already redeemed.
invalid_token	400	invalid_cashu_token	No	The token is malformed or cannot be decoded.
mint_error	422	cashu_token_swap_fees_exceed_amount	No	Token value is too small to cover the mint's NUT-02 input fees.
untrusted_mint	400	cashu_untrusted_source_mint	No	The token was issued by a mint this node does not accept. Only the node's configured mints (PRIMARY_MINT_URL / CASHU_MINTS) are redeemable.
mint_unreachable	503	cashu_source_mint_unreachable	Yes	The mint that issued the token could not be reached; it cannot be redeemed at another mint.
mint_rate_limited	503	cashu_mint_rate_limited	Yes	The mint rate-limited the request; retry after the cooldown.
mint_timeout	503	cashu_mint_timeout	Yes	The mint did not respond in time; retry later.
mint_unreachable	503	cashu_mint_unreachable	Yes	The mint could not be reached (DNS failure, refused/reset connection). The token is fine — retry once the mint recovers.
cashu_error	400	cashu_token_redemption_failed	No	The token could not be redeemed for another expected reason.
cashu_error	400	cashu_token_zero_value	No	The token redeemed to zero (empty/dust token, or value fully consumed by fees).
token_consumed	500	cashu_token_consumed	No	The token was spent (melted/redeemed) but crediting it then failed. Do not retry — the token is gone; contact support to reconcile.
api_error	500	internal_error	Maybe	Unexpected server-side fault during redemption.

!!! important "Retry only transient mint failures" Only mint_unreachable, mint_rate_limited and mint_timeout (503) are retryable — the same token may work again later. Everything else is a permanent property of the token and must not be blindly retried. untrusted_mint is permanent: the node will never accept that mint until an operator adds it to CASHU_MINTS. Use exponential backoff for the 503 responses, and honor the mint's cooldown for mint_rate_limited. In particular, a token_consumed 500 means the mint already spent the token, so a retry would fail as token_already_spent.

Mint failures (retryable)

mint_unreachable, mint_rate_limited and mint_timeout are retryable redemption errors. For mint_rate_limited, honor the mint's cooldown before retrying.

{
  "error": {
    "type": "mint_unreachable",
    "message": "Cashu mint is unreachable",
    "code": "cashu_mint_unreachable"
  }
}

Status: 503

Resolution: The token is valid — the mint is temporarily down. Retry with backoff, or pay with a token from a different mint. If the mint returns mint_rate_limited, wait for its cooldown before retrying.

Token Already Spent

{
  "error": {
    "type": "token_already_spent",
    "message": "Cashu token already spent",
    "code": "cashu_token_already_spent"
  }
}

Status: 400

Resolution: Use a fresh, unspent token. Do not retry with the same token.

Response envelope differs by endpoint

The error object above is identical everywhere, but the surrounding envelope depends on how you paid:

• X-Cashu header payments (chat + Responses API) return the object at the top level, alongside a request_id:

  {
    "error": { "type": "mint_unreachable", "message": "Cashu mint is unreachable", "code": "cashu_mint_unreachable" },
    "request_id": "req-abc123"
  }
  

  The original token is echoed back in the X-Cashu response header only when it is still spendable (e.g. mint_unreachable, mint_rate_limited, invalid_cashu_token, fee errors) so you can recover/retry it. It is not echoed for spent/consumed tokens (cashu_token_already_spent, cashu_token_consumed, cashu_token_zero_value, internal_error) — retrying those can never succeed.

• Authorization: Bearer <cashu-token> (API key minting) wraps it in FastAPI's detail field:

  { "detail": { "error": { "type": "mint_unreachable", "message": "Cashu mint is unreachable", "code": "cashu_mint_unreachable" } } }
  

• POST /v1/wallet/topup returns the same structured envelope wrapped in FastAPI's detail field, identical to the bearer path:

  { "detail": { "error": { "type": "mint_unreachable", "message": "Cashu mint is unreachable", "code": "cashu_mint_unreachable" } } }
  

Validation Errors

Invalid Parameters

{
  "error": {
    "type": "invalid_request",
    "message": "Invalid request parameters",
    "code": "validation_error",
    "details": {
      "errors": [
        {
          "field": "temperature",
          "message": "Must be between 0 and 2",
          "value": 3.5
        },
        {
          "field": "model",
          "message": "Model 'gpt-5' not found",
          "value": "gpt-5"
        }
      ]
    }
  }
}

Status: 422
Resolution: Fix parameter values

Missing Required Fields

{
  "error": {
    "type": "invalid_request",
    "message": "Missing required fields",
    "code": "missing_fields",
    "details": {
      "missing": ["model", "messages"]
    }
  }
}

Status: 400
Resolution: Include all required fields

Rate Limiting

Rate Limit Exceeded

{
  "error": {
    "type": "rate_limit_exceeded",
    "message": "Too many requests",
    "code": "rate_limit",
    "details": {
      "limit": 100,
      "window": "1 minute",
      "retry_after": 45
    }
  }
}

Status: 429
Headers:

X-RateLimit-Limit: 100
X-RateLimit-Remaining: 0
X-RateLimit-Reset: 1640995200
Retry-After: 45

Resolution: Wait for retry_after seconds

Upstream Errors

Upstream Unavailable

A provider returned a 5xx (overloaded, bad gateway, timeout, or a provider-side outage). This node is healthy and your reservation has been reverted.

{
  "error": {
    "type": "upstream_error",
    "message": "Model is currently overloaded",
    "code": "UPSTREAM_UNAVAILABLE",
    "upstream_status": 503,
    "details": {
      "model": "gpt-4",
      "retry_after": 5
    }
  }
}

Status: 424
Header: X-Routstr-Error-Scope: upstream
Resolution: Retry after a short backoff. If the node is configured with alternative providers for the model, it already retried them before answering — try another model or provider path if the failure persists.

Upstream Timeout

{
  "error": {
    "type": "upstream_error",
    "message": "Request to upstream API timed out",
    "code": "upstream_timeout",
    "details": {
      "timeout": 30,
      "endpoint": "chat/completions"
    }
  }
}

Status: 424
Header: X-Routstr-Error-Scope: upstream
Resolution: Retry with shorter prompt or max_tokens

Content Policy

Content Filtered

{
  "error": {
    "type": "content_policy_violation",
    "message": "Content filtered due to policy violation",
    "code": "content_filtered",
    "details": {
      "reason": "harmful_content",
      "categories": ["violence", "hate"]
    }
  }
}

Status: 400
Resolution: Modify prompt to comply with policies

Error Handling Best Practices

Retry Logic

Implement exponential backoff with jitter:

import time
import random
from typing import Optional, Callable

def retry_with_backoff(
    func: Callable,
    max_retries: int = 3,
    base_delay: float = 1.0,
    max_delay: float = 60.0
) -> Optional[Any]:
    """Retry function with exponential backoff."""
    
    for attempt in range(max_retries):
        try:
            return func()
        except Exception as e:
            if attempt == max_retries - 1:
                raise
            
            # Check if error is retryable
            if hasattr(e, 'status_code'):
                if e.status_code in [424, 429, 502, 503, 504]:
                    # Calculate delay with jitter
                    delay = min(
                        base_delay * (2 ** attempt) + random.uniform(0, 1),
                        max_delay
                    )
                    
                    # Use retry_after if provided
                    if hasattr(e, 'retry_after'):
                        delay = e.retry_after
                    
                    time.sleep(delay)
                else:
                    # Non-retryable error
                    raise

Error Categories

Group errors for handling:

class ErrorHandler:
    # Errors that should be retried
    RETRYABLE_ERRORS = {
        'UPSTREAM_UNAVAILABLE',  # upstream 5xx, reported as HTTP 424
        'UPSTREAM_RATE_LIMIT',   # HTTP 429
        'UPSTREAM_TIMEOUT',      # EHBP upstream timeout, reported as HTTP 424
        'rate_limit',
        'upstream_timeout',
        'model_overloaded',
        'cashu_mint_unreachable'
    }
    
    # Errors requiring user action
    USER_ACTION_ERRORS = {
        'insufficient_balance',
        'invalid_api_key',
        'key_expired'
    }
    
    # Errors requiring code changes
    CLIENT_ERRORS = {
        'validation_error',
        'missing_fields',
        'invalid_request'
    }
    
    @classmethod
    def handle_error(cls, error_response: dict) -> None:
        error_code = error_response['error']['code']
        
        if error_code in cls.RETRYABLE_ERRORS:
            # Implement retry logic
            pass
        elif error_code in cls.USER_ACTION_ERRORS:
            # Alert user
            pass
        elif error_code in cls.CLIENT_ERRORS:
            # Log for debugging
            pass

Graceful Degradation

Handle errors without breaking application flow:

async def get_ai_response(prompt: str) -> str:
    """Get AI response with fallback handling."""
    try:
        # Try primary model
        response = await client.chat.completions.create(
            model="gpt-4",
            messages=[{"role": "user", "content": prompt}]
        )
        return response.choices[0].message.content
    
    except InsufficientBalanceError:
        # Fall back to cheaper model
        try:
            response = await client.chat.completions.create(
                model="gpt-3.5-turbo",
                messages=[{"role": "user", "content": prompt}],
                max_tokens=100  # Limit tokens
            )
            return response.choices[0].message.content
        except Exception as e:
            logger.error(f"Fallback failed: {e}")
            return "Service temporarily unavailable"
    
    except Exception as e:
        logger.error(f"Unexpected error: {e}")
        return "An error occurred processing your request"

Logging Errors

Structure error logs for debugging:

import logging
import json

def log_api_error(error_response: dict, context: dict) -> None:
    """Log API errors with context."""
    logger = logging.getLogger(__name__)
    
    error_data = {
        'timestamp': datetime.utcnow().isoformat(),
        'error': error_response['error'],
        'context': {
            'endpoint': context.get('endpoint'),
            'api_key_id': context.get('api_key_id'),
            'request_id': context.get('request_id'),
            'model': context.get('model')
        }
    }
    
    logger.error(
        "API Error",
        extra={'structured_data': json.dumps(error_data)}
    )

User-Friendly Messages

Map technical errors to user messages:

ERROR_MESSAGES = {
    'insufficient_balance': "Your account balance is too low. Please add funds to continue.",
    'invalid_api_key': "Invalid API key. Please check your configuration.",
    'rate_limit': "Too many requests. Please wait a moment and try again.",
    'model_overloaded': "The AI service is busy. Please try again in a few seconds.",
    'validation_error': "Invalid request. Please check your input and try again."
}

def get_user_message(error_code: str) -> str:
    """Get user-friendly error message."""
    return ERROR_MESSAGES.get(
        error_code,
        "An unexpected error occurred. Please try again later."
    )

Common Scenarios

Handling Balance Errors

async def make_request_with_balance_check():
    try:
        # Check balance first
        balance_info = await client.get("/v1/wallet/balance")
        
        # Estimate cost
        estimated_cost = calculate_cost(model, prompt_length)
        
        if balance_info['balance'] < estimated_cost * 1.1:  # 10% buffer
            # Proactively top up
            await top_up_balance()
        
        # Make request
        return await client.chat.completions.create(...)
        
    except InsufficientBalanceError as e:
        # Handle insufficient balance
        shortfall = e.details['shortfall']
        await top_up_balance(amount=shortfall * 2)
        # Retry request

Handling Rate Limits

from datetime import datetime, timedelta

class RateLimitTracker:
    def __init__(self):
        self.reset_times = {}
    
    def is_limited(self, endpoint: str) -> bool:
        reset_time = self.reset_times.get(endpoint)
        if reset_time and datetime.now() < reset_time:
            return True
        return False
    
    def set_limit(self, endpoint: str, reset_timestamp: int):
        self.reset_times[endpoint] = datetime.fromtimestamp(reset_timestamp)
    
    def wait_time(self, endpoint: str) -> float:
        reset_time = self.reset_times.get(endpoint)
        if reset_time:
            return max(0, (reset_time - datetime.now()).total_seconds())
        return 0

Testing Error Handling

Unit Tests

import pytest
from unittest.mock import Mock

async def test_insufficient_balance_handling():
    # Mock API client
    mock_client = Mock()
    mock_client.chat.completions.create.side_effect = InsufficientBalanceError(
        required=100,
        available=50
    )
    
    # Test error handling
    handler = ErrorHandler(mock_client)
    result = await handler.safe_request(
        model="gpt-4",
        messages=[{"role": "user", "content": "test"}]
    )
    
    # Verify fallback behavior
    assert result.fallback_used is True
    assert result.model == "gpt-3.5-turbo"

Integration Tests

async def test_real_error_scenarios():
    # Test with invalid API key
    invalid_client = OpenAI(
        api_key="sk-invalid",
        base_url=test_url
    )
    
    with pytest.raises(AuthenticationError) as exc_info:
        await invalid_client.chat.completions.create(
            model="gpt-3.5-turbo",
            messages=[{"role": "user", "content": "test"}]
        )
    
    assert exc_info.value.status_code == 401
    assert "invalid_api_key" in str(exc_info.value)

Monitoring Errors

Track error rates and patterns:

class ErrorMetrics:
    def __init__(self):
        self.error_counts = defaultdict(int)
        self.error_timestamps = defaultdict(list)
    
    def record_error(self, error_code: str):
        self.error_counts[error_code] += 1
        self.error_timestamps[error_code].append(datetime.now())
    
    def get_error_rate(self, error_code: str, window_minutes: int = 60) -> float:
        cutoff = datetime.now() - timedelta(minutes=window_minutes)
        recent_errors = [
            ts for ts in self.error_timestamps[error_code]
            if ts > cutoff
        ]
        return len(recent_errors) / window_minutes

Next Steps

• Authentication - Auth error details
• Endpoints - Endpoint-specific errors
• Integration Guide - Error handling examples