Anthropic Reliability Patterns

Overview

Build fault-tolerant Claude integrations with built-in SDK retries, model fallback chains (Sonnet → Haiku), circuit breakers to avoid hammering a failing API, graceful degradation with cached/static responses, and per-request timeout configuration.

Built-In SDK Retries

The SDK retries 429 (rate limit) and 529 (overloaded) automatically:

const client = new Anthropic({
  maxRetries: 3, // default: 2
  timeout: 120_000, // 2 minutes
});

Model Fallback Chain

const FALLBACK_CHAIN = ['claude-sonnet-4-20250514', 'claude-haiku-4-5-20251001'];

async function callWithFallback(params: Anthropic.MessageCreateParams) {
  for (const model of FALLBACK_CHAIN) {
    try {
      return await client.messages.create({ ...params, model });
    } catch (err) {
      if (err instanceof Anthropic.APIError && err.status >= 500) {
        console.warn(`${model} failed (${err.status}), trying next...`);
        continue;
      }
      throw err; // Don't retry client errors (4xx)
    }
  }
  throw new Error('All models failed');
}

Circuit Breaker

class ClaudeCircuitBreaker {
  private failures = 0;
  private lastFailure = 0;
  private readonly threshold = 5;
  private readonly resetMs = 60_000;

  async call(params: Anthropic.MessageCreateParams) {
    if (this.failures >= this.threshold && Date.now() - this.lastFailure < this.resetMs) {
      throw new Error('Circuit open — Claude API unavailable');
    }

    try {
      const result = await client.messages.create(params);
      this.failures = 0;
      return result;
    } catch (err) {
      if (err instanceof Anthropic.APIError && err.status >= 500) {
        this.failures++;
        this.lastFailure = Date.now();
      }
      throw err;
    }
  }
}

Graceful Degradation

async function getResponse(userInput: string): Promise<string> {
  try {
    const message = await client.messages.create({
      model: 'claude-sonnet-4-20250514',
      max_tokens: 1024,
      messages: [{ role: 'user', content: userInput }],
    });
    return message.content[0].text;
  } catch (err) {
    // Return cached/static response instead of failing
    console.error('Claude unavailable, using fallback');
    return "I'm temporarily unable to process your request. Please try again shortly.";
  }
}