How to fix “Cannot connect to Anthropic” network errors in n8n?

The fast fix is this: in n8n, “Cannot connect to Anthropic” almost always means a networking or TLS problem between your n8n server and Anthropic’s API endpoint. The most common real causes are missing outbound internet access, a corporate proxy or firewall blocking traffic, incorrect API base URL, or DNS/TLS issues inside the Docker container. Fixing it means confirming your n8n host can reach api.anthropic.com, verifying your Anthropic credentials, and checking that Docker/n8n isn’t blocked from making outbound HTTPS requests.

 

What Usually Causes This in Real n8n Deployments

 

• No outbound network from the server or container — firewalls, corporate networks, or cloud security groups block HTTPS to Anthropic.
• DNS issues inside Docker — container cannot resolve api.anthropic.com even though the host can.
• Wrong base URL — Anthropic changed to https://api.anthropic.com; older URLs like api.anthropic.ai no longer work.
• Wrong model name — if the node references a model that doesn’t exist, the request sometimes fails before reaching the API.
• SSL/TLS middleware problems — some corporate proxies break TLS; n8n throws “Cannot connect” even though the API is reachable from outside.
• Self-hosted n8n behind a proxy without proper proxy env vars — n8n does not know how to route outbound HTTPS through your proxy.

 

Step-by-Step Fix

 

Here’s the clean, reliable way to debug it like we do in production.

• Test connectivity from the host machine
  Run this directly on the server (not in Docker yet):
  \`\`\`bash curl -I https://api.anthropic.com ```
  If this times out or fails TLS, your network/firewall is blocking it.
• Test connectivity from inside the n8n Docker container
  This is the real test, because n8n runs inside the container:
  ```bash docker exec -it n8n curl -I https://api.anthropic.com ```
  If host works but Docker fails, it’s a DNS or networking issue in the container.
• Confirm your Anthropic API key in n8n Credentials
  Use exactly the "sk-ant-" style key.
  Make sure no spaces, no line breaks.
• Confirm the Base URL in the Anthropic node
  It should be:
  https://api.anthropic.com
• Make sure you’re using valid models — for example:
  • claude-3-5-sonnet-latest
  • claude-3-opus-latest
• If behind corporate proxy, set proxy variables for n8n
  Add to your n8n environment:
  ```bash HTTP_PROXY=http://your-proxy:port HTTPS_PROXY=http://your-proxy:port NO_PROXY=localhost,127.0.0.1 ```
  Restart the container afterward.
• If using n8n Cloud, check IP allowlists
  Some Anthropic accounts or firewalls require allowlisting the source IP.
  n8n Cloud uses outgoing shared IPs, and Anthropic may block them if not allowed.

 

The Hidden Gotcha: TLS and Intermediate Certificates

 

A frequent real-world issue: older Docker images or custom Linux containers don’t have updated CA certificates. Anthropic’s TLS chain requires up‑to‑date cert bundles, and an outdated system causes n8n to throw “Cannot connect”.

To fix that:

• Update system CA certificates inside your container:
  ```bash docker exec -it n8n apk update && apk add ca-certificates ```
  (for Alpine-based images)

 

If You Need a Guaranteed Check from Inside n8n

 

Create a simple Workflow with an HTTP Request node:

// Method: GET
// URL: https://api.anthropic.com
// Authentication: None
\`\`\`

<p>If this node also fails, the issue is definitely network/TLS, not your Anthropic node configuration.</p>

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<h3>Bottom Line</h3>

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<p>“Cannot connect to Anthropic” in n8n is almost never the Anthropic node itself. It’s usually network reachability, DNS inside Docker, TLS certificate issues, or outdated base URLs. Solve it by testing connectivity from the host and inside the container, confirming your credentials and base URL, and fixing any proxy/firewall or CA certificate problems.</p>