Fix Claude SDK Connection & Timeout Errors

When integrating Claude into your application using official Python (anthropic) or TypeScript/JavaScript (@anthropic-ai/sdk) libraries, connection errors can disrupt your environment. These failures usually manifest as timeout exceptions, connection drops, SSL verification failures, or DNS resolution issues.

Use this troubleshooting checklist to isolate and resolve your Claude SDK connection issues.

Step 1: Verify Environment Variables and Client Initialization

The SDK relies on proper client instantiation to resolve API endpoints and load keys. Connection errors often occur when the SDK cannot authenticate or resolve server pathways.

1. Verify your API key is correctly loaded. In Python, ensure os.environ.get("ANTHROPIC_API_KEY") returns the key. In Node.js, verify process.env.ANTHROPIC_API_KEY is populated. 2. Check your client initialization. Do not pass manual header strings unless customizing the request. Use the standard setup: * Python: `python from anthropic import Anthropic client = Anthropic() # Automatically loads ANTHROPIC_API_KEY ` * Node.js: `javascript import Anthropic from '@anthropic-ai/sdk'; const anthropic = new Anthropic(); // Automatically loads process.env.ANTHROPIC_API_KEY `

Step 2: Resolve SSL Certificate and Handshake Failures

If your local network, corporate firewall, or VPN intercepts HTTPS requests, your SDK might fail with an SSL/TLS verification error (e.g., SSLCertVerificationError in Python or DEPTH_ZERO_SELF_SIGNED_CERT in Node.js).

1. Ensure your local operating system and browser trust store are up to date. Outdated Root CA certificates frequently block API requests.
2. If you are behind a corporate proxy that uses self-signed SSL certificates, configure the SDK to use your network's custom CA bundle rather than disabling SSL validation completely.
3. In Python, you can specify your system's cert bundle by setting the SSL_CERT_FILE or REQUESTS_CA_BUNDLE environment variables pointing to your cacert.pem file.

Step 3: Configure Proxy Settings in the SDK

If your runtime environment requires traffic to go through an explicit HTTP/HTTPS proxy, the Claude SDK must be configured to pass its traffic through that proxy, or requests will time out.

1. Python SDK: The Python SDK uses httpx under the hood. You can pass a pre-configured httpx.Client to your Anthropic initializer with proxy rules. `python import httpx from anthropic import Anthropic

client = Anthropic( http_client=httpx.Client(proxies="http://my.proxy.server:8080") ) ` 2. Node.js SDK: Use an HTTP agent like https-proxy-agent to route traffic through your proxy server. `javascript import Anthropic from '@anthropic-ai/sdk'; import { HttpsProxyAgent } from 'https-proxy-agent';

const anthropic = new Anthropic({ httpAgent: new HttpsProxyAgent('http://my.proxy.server:8080'), }); `

Step 4: Adjust Client Timeout Settings

Large context window requests or heavy generative payloads take time. If your connection drops halfway through a response, your local timeout settings might be too aggressive.

1. Increase the default connection timeout window within your SDK initialization block. 2. Python: Pass a custom timeout float value (in seconds) or use the helper class. `python from anthropic import Anthropic client = Anthropic(timeout=60.0) # Set timeout limit to 60 seconds ` 3. Node.js: Set the timeout property during client initialization. `javascript const anthropic = new Anthropic({ timeout: 60 * 1000, // 60 seconds }); `

Step 5: Update the SDK Package

Using deprecated versions of SDK packages can cause connection drops or failures to read modern endpoints.

1. Update your installed SDK dependencies to the latest versions:
2. Python: pip install --upgrade anthropic
3. Node.js: npm update @anthropic-ai/sdk
4. Ensure your local runtime (Python 3.8+ or Node.js 18+) matches the minimum supported versions of the SDK packages.

When to Escalate

If your local configurations are correct but connections consistently drop with a 502 Bad Gateway, 503 Service Unavailable, or 504 Gateway Timeout error, check the Anthropic Status Page for system-wide API degradation. If your local tracer indicates connection failures occur only on your specific cloud hosting infrastructure (e.g., AWS EC2, GCP Cloud Run), verify that your cloud outbound firewall rules or VPC security groups permit TCP traffic on port 443 to api.anthropic.com.