API Base URL, API Key, and Model Name Troubleshooting

When an API setup fails, do not switch models immediately. Most issues come from three fields: Base URL, API Key, and model name.

First identify your client type

OpenAI-compatible clients

Examples include Cline, ChatBox, NextChat, Cherry Studio, and many custom apps. They usually need:

• Base URL: https://api.cheng-zi-ai.com/v1
• API Key: sk-...
• Model ID: a model name from the console

Claude Code

Claude Code uses Anthropic-style environment variables. It usually needs:

• ANTHROPIC_BASE_URL=https://api.cheng-zi-ai.com
• ANTHROPIC_AUTH_TOKEN=sk-...
• ANTHROPIC_MODEL=claude-opus-4-8

Key difference: OpenAI-compatible clients usually include /v1, while Claude Code's ANTHROPIC_BASE_URL usually does not.

Recommended debug order

1. Confirm the Base URL.
2. Confirm the key was copied completely with no extra spaces.
3. Confirm the Model ID came from the console.
4. Test with a very short prompt.
5. Then check credits, permissions, and rate limits.

401 or Invalid API Key

Common causes:

• The key was copied partially.
• The key was deleted or disabled.
• The key was pasted into the wrong field.
• Claude Code has both ANTHROPIC_API_KEY and ANTHROPIC_AUTH_TOKEN, and the older variable is taking precedence.

Fix:

1. Copy the key again.
2. Clear old environment variables or old client settings.
3. Save and test again.

404, Model Not Found, or missing model

Common causes:

• The model name was typed incorrectly.
• The key does not have access to that model.
• The client rewrote the model name.
• The Base URL points to a different service.

Fix: copy the model name from the console, test with a known available model first, then switch to a stronger or more expensive model.

Connection Error or Network Error

Common causes:

• An OpenAI-compatible client is missing /v1.
• Claude Code was configured with /v1 by mistake.
• A local network or proxy is blocking the request.
• The client cached old settings.

Fix: restart the client and test again with the smallest possible configuration.

Quick self-check

OpenAI-compatible clients should look like this:

Base URL: https://api.cheng-zi-ai.com/v1
API Key: sk-your-api-key
Model ID: gpt-5.3-codex

Claude Code should look like this:

ANTHROPIC_BASE_URL=https://api.cheng-zi-ai.com
ANTHROPIC_AUTH_TOKEN=sk-your-api-key
ANTHROPIC_MODEL=claude-opus-4-8

If you are not sure which type your client is, check whether it asks you to choose an OpenAI Compatible Provider. If it does, use the OpenAI-compatible setup.