Claude API Error Codes Explained

Error code quick reference

529 Overloaded — the full picture

Retry pattern (Python)

import anthropic, time, random

client = anthropic.Anthropic()

def call_with_backoff(prompt: str, max_retries: int = 6):
    delay = 1.0
    for attempt in range(max_retries):
        try:
            return client.messages.create(
                model="claude-sonnet-5",
                max_tokens=1024,
                messages=[{"role": "user", "content": prompt}],
            )
        except anthropic.RateLimitError:          # 429
            raise                                  # your rate limit — fix at source
        except anthropic.APIStatusError as e:
            if e.status_code in (529, 503, 500) and attempt < max_retries - 1:
                jitter = random.uniform(0, 0.3 * delay)
                time.sleep(delay + jitter)
                delay = min(delay * 2, 60)
                continue
            raise
    raise RuntimeError("Max retries exceeded")

Retry pattern (TypeScript)

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

const client = new Anthropic();

async function callWithBackoff(prompt: string, maxRetries = 6) {
  let delay = 1000;
  for (let attempt = 0; attempt < maxRetries; attempt++) {
    try {
      return await client.messages.create({
        model: "claude-sonnet-5",
        max_tokens: 1024,
        messages: [{ role: "user", content: prompt }],
      });
    } catch (err: any) {
      const status = err?.status;
      if ([529, 503, 500].includes(status) && attempt < maxRetries - 1) {
        const jitter = Math.random() * delay * 0.3;
        await new Promise((r) => setTimeout(r, delay + jitter));
        delay = Math.min(delay * 2, 60_000);
        continue;
      }
      throw err;
    }
  }
}

429 Rate Limit — diagnose and fix

Frequently asked questions