Fix Claude API Error 500 -- Internal Server Error

TL;DR: A 500 error means Anthropic's servers failed to process your request. Retry with exponential backoff, validate your payload, and check the status page before escalating.

The Problem

When calling the Claude API, you receive an HTTP 500 response:

{
  "type": "error",
  "error": {
    "type": "api_error",
    "message": "Internal server error"
  }
}

Why This Happens

HTTP 500 is a server-side error. Common triggers include:

• Temporary infrastructure issues during peak usage periods or deployments
• Malformed request payloads that pass initial validation but fail during processing
• Large or complex requests that exceed internal processing limits

The Fix

Step 1: Implement Exponential Backoff Retry

Python SDK:

import anthropic

client = anthropic.Anthropic(max_retries=3)

try:
    response = client.messages.create(
        model="claude-sonnet-4-5-20250514",
        max_tokens=1024,
        messages=[{"role": "user", "content": "Hello"}]
    )
except anthropic.InternalServerError as e:
    print(f"Server error after retries: {e.status_code}")

TypeScript SDK:

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({ maxRetries: 3 });

try {
    const response = await client.messages.create({
        model: "claude-sonnet-4-5-20250514",
        max_tokens: 1024,
        messages: [{ role: "user", content: "Hello" }],
    });
} catch (error) {
    if (error instanceof Anthropic.InternalServerError) {
        console.error(\`Server error: \${error.status}\`);
    }
}

Step 2: Validate Your Request Payload

Common payload issues that trigger 500 instead of 400:

• Mixing tool_choice: "required" with no tools defined
• Using output_format with unsupported schema combinations
• Sending cache_control on models that do not support prompt caching

Step 3: Check Anthropic Status Page

curl -s https://status.anthropic.com/api/v2/status.json | python3 -c "
import json, sys
data = json.load(sys.stdin)
print(f'Status: {data["status"]["indicator"]} -- {data["status"]["description"]}')"

Common Variations

Prevention

• Always configure retries: Set max_retries=3 or higher for production.
• Monitor the status page: Subscribe to status.anthropic.com for incident notifications.
• Log request IDs: Include the x-request-id response header in your logs.