Use Claude Code, Cursor and Cline with one OpenAI-compatible key (GPT, Claude, Gemini, DeepSeek)

#ai #api #llm #tools

Disclosure: I work on 666 AI, the gateway used in the examples below. The setup pattern works with any OpenAI-compatible gateway.

If you switch between models a lot, you end up with several API keys, several bills, and a different config in every tool. Gateways fix that: one key, one balance, and the tool only needs two fields changed — the base URL and the key.

Below are working configs for the most common tools.

1. The two values you need

Base URL (OpenAI format): https://YOUR-ENDPOINT/v1
Base URL (Anthropic format, for Claude Code): https://YOUR-ENDPOINT — note: no /v1
Key: sk-... from your gateway console

Quick check that it works:

curl https://YOUR-ENDPOINT/v1/chat/completions \
  -H "Authorization: Bearer $KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"deepseek-v4-flash","messages":[{"role":"user","content":"hi"}]}'

A JSON response means you're done.

2. Claude Code

Claude Code speaks the Anthropic protocol, so point it at the Anthropic-format address:

# ~/.zshrc or ~/.bashrc
export ANTHROPIC_BASE_URL="https://YOUR-ENDPOINT"
export ANTHROPIC_AUTH_TOKEN="YOUR_KEY"

Reopen the terminal and run claude. The most common mistake is adding /v1 here — don't.

3. Cursor

Settings → Models → OpenAI API Key
Turn on Override OpenAI Base URL
Paste https://YOUR-ENDPOINT/v1 and your key, click Verify
Add the model names you want to use (e.g. claude-sonnet-5-5, gemini-3.5-flash)

4. Cline / Roo Code

API Provider: OpenAI Compatible
Base URL: https://YOUR-ENDPOINT/v1
API Key: your key
Model ID: any model from the catalog

5. Python / Node (official SDKs, unchanged)

from openai import OpenAI

client = OpenAI(api_key="YOUR_KEY", base_url="https://YOUR-ENDPOINT/v1")
resp = client.chat.completions.create(
    model="claude-sonnet-5-5",
    messages=[{"role": "user", "content": "Explain this regex: ^\\d{3}-\\d{4}$"}],
)
print(resp.choices[0].message.content)

Switching models is now a one-word change (claude-sonnet-5-5 → gemini-3.5-flash → deepseek-v4-flash), with no new SDK and no new key.

Things worth knowing

Streaming, tool calling and vision work the same as the official APIs, as long as the model supports them.
Prompt caching: put the unchanging part (system prompt, project files) first and the varying part last. The order decides the cache hit rate, and cached tokens are billed much cheaper.
Set a spend cap per key, and use one key per project. If a key leaks, you lose one project's budget, not everything.

Why bother

A common split is Claude for refactors, DeepSeek for cheap bulk tasks and Gemini for long documents. With all three behind one key, the editor config never changes. Only the model name does.

If you want to try the gateway in these examples, signup is free and there's a daily free chat allowance: 666gogogo.com. Full docs: Documentation.

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