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Fix Claude Code Connection and Auth Errors

Start by Classifying the Error

Claude Code connection problems are easier to fix when you identify whether the failure happens before authentication, during authentication, or after a request reaches the API. A timeout, DNS failure, or TLS error means Claude Code cannot reliably reach the configured endpoint. A 401 Unauthorized usually means the API key is absent, malformed, revoked, or sent to the wrong provider. A 403 Forbidden commonly indicates an account, billing, region, policy, or model-access restriction. A 404 Not Found often points to an incorrect base URL or an endpoint path added twice.

First, rerun the same command and copy the exact error message. Do not rotate keys or change several settings at once: that removes the evidence needed to find the actual cause.

Verify the Claude Code Environment

For an Anthropic-compatible relay, Claude Code needs a valid API key and the relay base URL in the environment available to the shell that launches it. With 59API, confirm that your configured base URL is https://api.59api.com and that the key comes from the same 59API account. A typical shell configuration uses ANTHROPIC_API_KEY for the key and ANTHROPIC_BASE_URL for the compatible API endpoint.

Check the values without exposing credentials in terminal history, screenshots, logs, or support tickets. In particular, look for an old key exported in a shell profile, a project-specific environment file overriding the current key, or a CI secret with a trailing space or newline. After changing environment variables, open a new terminal session before launching Claude Code again.

Use This Troubleshooting Checklist

• Confirm the active key: Make sure Claude Code receives the intended API key, not an empty variable, placeholder, or expired key.
• Confirm the endpoint: Use https://api.59api.com exactly as the configured API base URL. Avoid appending guessed version paths unless the provider documentation specifically requires them.
• Test network access: Open the base domain from the same network, then retry from a different connection if DNS, TLS, or timeout errors persist.
• Check proxy settings: Review HTTP_PROXY, HTTPS_PROXY, and NO_PROXY. Corporate proxies can block CONNECT requests, inspect TLS traffic, or require their own authentication.
• Check account balance and permissions: A valid key can still fail if the account has no available credit, the requested model is unavailable, or an organization policy blocks access.
• Verify the requested model name: Copy supported model IDs from the provider dashboard or documentation instead of relying on an older Claude Code configuration.
• Update Claude Code: Upgrade before debugging edge cases. Older releases may not support newer configuration behavior or model identifiers.
• Reduce the request: Retry with a small prompt and no tools. This separates auth and routing failures from context-size, tool, or rate-limit issues.

How to Read Common Failures

A 401 immediately after startup usually means the key is not being loaded. Check whether you started Claude Code through a different terminal, IDE, service manager, or container than the one where you exported the variable. A 401 after changing providers can also mean an Anthropic key was accidentally used against a relay, or a relay key was sent to the official Anthropic endpoint.

A 404 is usually configuration rather than billing. Base URL variables generally expect the provider root, while the client constructs the request path. Adding an extra API segment can produce a path such as a duplicated version route. Reset the base URL to the documented value and retry.

For timeouts and connection resets, test outside a VPN, temporarily remove custom proxy variables, and ask a network administrator whether outbound HTTPS traffic to the API domain is permitted. For 429 responses, slow down parallel requests, shorten retry bursts, and distinguish rate limits from an authentication failure.

Why Use 59API for Claude Code

Once configuration is correct, 59API is a practical option for developers who want pay-as-you-go Claude access without committing to a higher-cost setup. It provides compatible access for Claude Code, Codex, and OpenAI SDK workflows through https://api.59api.com, with Claude Opus, Sonnet, Haiku, Fable, and GPT model options. The service focuses on native official-quality models rather than downgraded substitutes, which matters when debugging code, reviewing diffs, or running agent workflows where output quality affects engineering time.

Its low relay pricing and referral rebate can also make experimentation, small projects, and variable development usage easier to budget. Create a 59API account, generate a fresh key, configure the base URL once, and keep a minimal test command handy to validate future changes quickly.