Use a custom endpoint with the OpenAI and Anthropic SDKs

Both official SDKs accept a base URL argument. That means switching billing routes is a one-line change — your request and response code stays exactly as it is.

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Quick self-check. Before wiring anything into your app, confirm the key works. This lists every model your account can call — it costs nothing and works from any machine:

curl https://aicomp.ai/v1/models \
  -H "Authorization: Bearer sk-your-gateway-key"

You should get back a JSON list of model IDs. If you see Invalid token, the key is wrong or was not copied in full.

Python — OpenAI SDK

from openai import OpenAI

client = OpenAI(
    base_url="https://aicomp.ai/v1",
    api_key="sk-your-gateway-key",   # not your OpenAI key
)

resp = client.chat.completions.create(
    model="gpt-5.6-luna",
    messages=[{"role": "user", "content": "say OK"}],
)
print(resp.choices[0].message.content)

Node — OpenAI SDK

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://aicomp.ai/v1",
  apiKey: "sk-your-gateway-key",
});

const r = await client.chat.completions.create({
  model: "gpt-5.6-luna",
  messages: [{ role: "user", content: "say OK" }],
});
console.log(r.choices[0].message.content);

Python — Anthropic SDK

import anthropic

client = anthropic.Anthropic(
    base_url="https://aicomp.ai/v1",
    api_key="sk-your-gateway-key",
)

msg = client.messages.create(
    model="claude-sonnet-5",
    max_tokens=64,
    messages=[{"role": "user", "content": "say OK"}],
)
print(msg.content[0].text)

Plain curl

curl https://aicomp.ai/v1/chat/completions \
  -H "Authorization: Bearer sk-your-gateway-key" \
  -H "Content-Type: application/json" \
  -d '{"model":"gpt-5.6-luna",
       "messages":[{"role":"user","content":"say OK"}]}'

Gotchas that cost people an hour

/v1 doubling. The OpenAI SDK appends /chat/completions. If your base URL already ends in /v1, do not include it twice.
Streaming. Server-sent events work on most gateways, but confirm before you rely on it in production.
Model IDs. Use the exact ID the gateway lists. gpt-5.6-luna and gpt-5.6-luna-2026-07-09 are different entries.
Timeouts. Set an explicit timeout. A gateway adds a hop, so budget slightly more than you would direct.

Migrating an existing codebase

Because only the client constructor changes, the safest rollout is to read the base URL from config:

import os
from openai import OpenAI

client = OpenAI(
    base_url=os.getenv("OPENAI_BASE_URL", "https://api.openai.com/v1"),
    api_key=os.getenv("OPENAI_API_KEY"),
)

Then switching route is an environment change, not a deploy.

Compare rates before you switch: all model prices, or run your volume through the cost calculator.

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