Fix Claude API Connection Error: Network, SDK Timeout, Claude Code, and Gateway Route Checks

If Claude API shows a connection error, first prove whether your request reached Anthropic. No HTTP status, no JSON body, or no request-id points to a connection-layer failure; a returned JSON error with a request ID belongs to the API error branch instead.

Start with this split:

Status note: this run checked Claude Status at 2026-04-29 19:04 Asia/Shanghai and the API and Claude Code surfaces were operational, but status is live data; check the current page before deciding the fault is local.

Stop rule: keep the failing path intact, change one variable per retry, and collect timestamp, region/network, route, SDK class, HTTP status if any, request ID if any, and same-path retry result before escalating.

Start With the Request-ID Boundary

The phrase Claude API connection error sounds simple, but it hides several different failure owners. The Claude Help Center connection-error article points first at firewall, network, and VPN restrictions. The Claude API error docs define returned API errors separately: a JSON error body carries error.type, error.message, and a request_id, and API responses include a request-id header. Those two facts give you the useful boundary.

Use the boundary this way: if the request never gets an HTTP response, the next evidence lives in connectivity, DNS, proxy, TLS, firewall, SDK timeout, or the route that sent the request. If the request returns a JSON error and a request ID, the API saw it. That does not mean the response is easy to fix, but it means you should stop treating it as a pure connection failure.

This distinction also protects you from bad first moves. Rotating keys, upgrading plans, reinstalling tools, or switching gateways before you know whether the request reached the API often destroys the only clean signal you have. Preserve the failing path first. Then choose the branch.

Run the 60-Second Same-Path Triage

The fastest useful triage is short and mechanical:

1. Open Claude Status and check the component that matches your route: Claude API, Claude Code, Console, or claude.ai.
2. Inspect the failure for an HTTP status, JSON body, request_id, or request-id header.
3. Confirm which route sent the request: direct api.anthropic.com, SDK, Claude Code, corporate proxy, VPN, gateway, or provider wrapper.
4. Retry the same payload on the same route after changing one variable, such as VPN off, proxy off, different network, longer timeout, or fresh Claude Code auth state.
5. Write down what changed and what stayed the same.

The same-path rule matters more than it sounds. If you change the key, prompt, model, network, timeout, and route at once, a successful retry tells you almost nothing. If you change only VPN state and the same request works, you have a network branch. If you increase timeout and the same long non-streaming request works, you have a timeout branch. If direct Anthropic works while a gateway route fails, you have a route branch.

Use Anthropic's connectivity-check guidance as the shape of the test: valid key, test request, then status code, response body, and error details. Do not paste secrets into tickets or logs. You need the route and error evidence, not the key.

Direct API Branch: Network, VPN, Firewall, Proxy, DNS, or TLS

Choose this branch when there is no HTTP status, no JSON error body, and no request ID. That combination usually means the client could not complete the path to the API endpoint. It can be a local machine problem, office firewall, VPN route, region-specific network path, corporate TLS inspection, proxy misconfiguration, DNS failure, or idle connection drop.

Start with the least destructive checks:

• Turn the VPN off for one retry, or move from a VPN to a trusted direct network.
• Try a second network such as mobile hotspot, home network, office network, or cloud runner in a different region.
• Confirm that firewall, allowlist, and proxy rules permit the Claude API endpoint you are actually using.
• Check DNS resolution and TLS handshake from the same environment where the request fails.
• If a corporate proxy terminates TLS, verify the proxy certificate path and client trust store.

The important phrase is "same environment." A browser reaching a help page does not prove that your backend worker, Docker container, CI runner, WSL shell, or serverless function can reach the API endpoint. Test from the process or host that sends the failing request.

If a different network fixes the same payload, the article should not tell you that Claude is down. It should tell you to document the network branch. If every network and host fails at the same time, and status or community reports are also noisy, then an Anthropic-side or regional route issue becomes more plausible. Keep the evidence dated.

SDK Branch: APIConnectionError, Timeout, and Returned API Errors

SDK errors are useful because they often tell you whether the failure was a no-response connection problem or a returned API problem. Anthropic's Python SDK docs and TypeScript SDK docs distinguish connection errors from status errors. In the Python SDK, APIConnectionError means the library could not connect to the API, while APIStatusError means the API returned a non-2xx response. In the TypeScript SDK, APIConnectionError maps to no available HTTP status, and timeout can surface as APIConnectionTimeoutError.

Handle Python like this:

python
import os
import anthropic

client = anthropic.Anthropic(
    timeout=60.0,
    max_retries=2,
)

try:
    message = client.messages.create(
        model=os.environ["ANTHROPIC_MODEL"],
        max_tokens=256,
        messages=[{"role": "user", "content": "Say hello in one sentence."}],
    )
except anthropic.APIConnectionError as exc:
    print("connection branch", type(exc).__name__, str(exc))
except anthropic.APIStatusError as exc:
    print("returned API branch", exc.status_code, exc.response.headers.get("request-id"))

For TypeScript, keep the same split:

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

const client = new Anthropic({
  timeout: 60_000,
  maxRetries: 2,
});

try {
  const message = await client.messages.create({
    model: process.env.ANTHROPIC_MODEL!,
    max_tokens: 256,
    messages: [{ role: "user", content: "Say hello in one sentence." }],
  });
} catch (error) {
  if (error instanceof Anthropic.APIConnectionTimeoutError) {
    console.error("timeout branch", error.message);
  } else if (error instanceof Anthropic.APIConnectionError) {
    console.error("connection branch", error.message);
  } else if (error instanceof Anthropic.APIError) {
    console.error("returned API branch", error.status, error.headers?.["request-id"]);
  }
}

Two SDK details matter for debugging. First, default retry behavior can hide the first failed attempt. Record final error time, retry count, and SDK version. Second, long non-streaming requests can fail because an intermediate network path drops idle connections. If the same prompt is long, tool-heavy, or slow to respond, test streaming or a longer timeout before calling it a generic outage.

Do not use SDK exception names as a plan-upgrade signal. APIConnectionError is not a rate-limit message. If the SDK gives you a returned HTTP error, leave this branch and classify that status. For 529, use the Claude API 529 overloaded error guide. For 429, use the Claude API rate-limit reached guide. For Claude Code-specific 500, use the Claude Code API Error 500 guide.

Claude Code Branch: Terminal Route, Auth State, and Environment

Use this branch when the visible symptom is inside Claude Code, especially terminal wording like API Error: Connection error. Claude Code can involve a different route owner than a direct SDK script: OAuth subscription route, ANTHROPIC_API_KEY, shell proxy variables, WSL networking, VS Code remote environment, corporate terminal proxy, or a provider wrapper.

Start inside Claude Code:

• Run /status and note the active authentication method and route.
• Check whether ANTHROPIC_API_KEY is set in the shell, IDE, WSL, container, or CI job that launched Claude Code.
• Compare terminal network variables such as HTTPS_PROXY, HTTP_PROXY, NO_PROXY, and custom CA settings.
• If the failure happens in WSL or VS Code remote, test from the same shell and from a plain local terminal.
• Avoid reinstalling before you know whether the route or auth owner changed.

The common trap is assuming Claude Code is using the same contract you had in mind. If ANTHROPIC_API_KEY is present, the request may be on an API-key route when you thought you were using a subscription login route. If a proxy variable is inherited by the terminal, the browser may work while Claude Code fails. If only WSL fails, the owner may be DNS, proxy, cert trust, or network bridging in that environment.

When the route is unclear, the better sibling is our Claude Code API configuration guide. If the symptom is not a connection error but a mixed 500/529/rate-limit situation in Claude Code, use the Claude Code 500, 529, and rate-limit router after you classify the returned error.

Gateway or Provider Branch: Use It as Isolation, Not a Shortcut

A gateway, proxy, or OpenAI-compatible provider route can be useful evidence, but it should not be the first explanation. Test direct Anthropic first when you can. Then compare the gateway route with the same prompt, model intention, timeout class, and input size. If direct works and the gateway fails, the likely owner is the gateway route, credential, model mapping, proxy, or compatibility layer. If direct fails and a gateway works, you have learned that an alternate route can reach a compatible surface, but you still have not proven the official API is generally down.

For developer teams that need a second route for isolation, laozhang.ai can be used as an API gateway option when the job is route comparison or compatible access testing. Keep that mention narrow. Do not treat it as a speed, uptime, quota, price, or refund claim unless those facts are verified in the same run. The diagnostic value is the controlled comparison, not a marketing promise.

The clean gateway test looks like this:

If the result changes, you know which variable deserves attention. If the result does not change, keep narrowing instead of changing three more variables.

When It Is Not a Connection Error Anymore

The moment you have a returned HTTP status or a JSON body with error.type, the recovery path changes. The request reached an API layer, even if the response is still a failure. Keep the request ID and classify the returned error.

Use this compact map:

This is where many troubleshooting threads go wrong. They keep saying "connection error" after the API has already returned an error object. That blurs the branch and leads to wrong fixes. A returned 429 needs usage/rate-limit handling, not VPN toggling. A returned 529 needs overload-aware retry behavior, not key rotation. A returned 500 needs a different incident and escalation story than a pure local DNS failure.

Escalate With a Minimal Evidence Packet

Escalate when the same path still fails after you have checked status, preserved the request-id boundary, tested the route owner, and changed one variable per retry. The packet should be short enough to send and precise enough for support or an internal platform team to route quickly.

Capture:

• timestamp and timezone
• SDK name, SDK version, runtime, host, and region
• exact error string and exception class
• HTTP status, error.type, error.message, and request ID if present
• active route: direct Anthropic, Claude Code, gateway, proxy, VPN, CI, WSL, container, or browser
• what Claude Status showed at the time
• one same-path retry result after one specific change
• redacted reproduction steps with secrets removed

Do not paste API keys, full prompts with private data, customer records, or raw proxy logs with credentials. If you need to show a request, redact the key and shorten the prompt to the smallest reproduction. The goal is not volume. The goal is branch clarity.

FAQ

What does a Claude API connection error usually mean?

It usually means the client could not complete the route to the API, especially when there is no HTTP status, no JSON error body, and no request ID. Start with status, network, VPN, firewall, proxy, DNS/TLS, SDK timeout, and route checks.

Should I rotate my API key first?

No. Key rotation is a poor first move for a no-response connection error. First prove whether the request reached the API, check the active route, and retry the same path after one network or timeout change. Rotate credentials only when the evidence points to auth or key ownership.

Does a green Claude Status page prove the problem is local?

No. A green status page only reduces the likelihood of a live incident on the checked component. It does not prove your network, SDK, Claude Code route, provider gateway, or regional path is healthy. Keep status as one data point.

Why do I see APIConnectionError in the SDK but no HTTP status?

That is the point of the connection branch. The SDK is telling you it did not receive a normal API response. Look at connectivity, timeout, proxy, DNS/TLS, VPN, firewall, and route ownership before classifying returned API statuses.

Is Claude Code API Error: Connection error the same problem?

It can share the same reachability boundary, but Claude Code has extra route and auth surfaces. Check /status, ANTHROPIC_API_KEY, proxy variables, terminal environment, WSL or VS Code path, and whether the tool is using the route you expected.

When should I use a gateway route?

Use a gateway route as an isolation test or operational route when direct access is blocked or when your team needs a compatible second path. Keep the comparison controlled, and avoid treating gateway success or failure as proof about Anthropic's entire service.

What should I send to support?

Send the timestamp, route, SDK/runtime, exact error string, HTTP status if any, request ID if any, current status-page note, same-path retry result, and redacted reproduction steps. Clean branch evidence is more useful than a long complaint.

The Working Rule

A Claude API connection error is a reachability problem until the request produces a response. Check current status, preserve the request-id boundary, choose the direct API, SDK, Claude Code, network/proxy, or gateway branch, change one variable, retry the same path, and escalate only when the evidence packet shows the same branch still failing.