OpenAI

Change three values — base URL, API key, and model id — and your existing OpenAI SDK works against AnyRouter. Your chat.completions and responses calls stay exactly the same. This guide is for anyone already calling the OpenAI API who wants one gateway, unified billing, and 180+ models.

Before you start

• An AnyRouter API key (prefixed sk-ar-). Create one in the dashboard.
• An existing OpenAI client (Python, TypeScript, or raw HTTP) you want to repoint.

What changes

Everything else — request bodies, streaming, error handling — is unchanged.

Before and after

The only diff is the base URL, the key, and the model id — same request body either way.

import OpenAI from "openai"

const client = new OpenAI({
  baseURL: "https://api.openai.com/v1",
  apiKey: process.env.OPENAI_API_KEY,
})

const completion = await client.chat.completions.create({
  model: "gpt-4o-mini",
  messages: [{ role: "user", content: "Summarize this pull request." }],
})

import OpenAI from "openai"

const client = new OpenAI({
  baseURL: "https://anyrouter.dev/api/v1",
  apiKey: process.env.ANYROUTER_API_KEY,
})

const completion = await client.chat.completions.create({
  model: "openai/gpt-5.4-mini",
  messages: [{ role: "user", content: "Summarize this pull request." }],
})

Migrate

const response = await client.responses.create({
  model: "openai/gpt-5.4-mini",
  input: "Extract the action items from this transcript.",
})

Verify

Send one request with your new key and confirm you get a reply:

curl https://anyrouter.dev/api/v1/chat/completions \
  -H "Authorization: Bearer sk-ar-your-key" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-5.4-mini",
    "messages": [{"role": "user", "content": "Write a release note."}]
  }'

List every model available to your key:

curl https://anyrouter.dev/api/v1/models -H "Authorization: Bearer sk-ar-your-key"

Routing preferences (optional)

Add a provider block to any request to cap price, prefer latency, or pin upstream order:

{
  "provider": {
    "sort": "latency",
    "max_price": { "prompt": "2.00", "completion": "8.00" },
    "allow_fallbacks": true
  }
}

See Provider Routing for every field.

Migrate with an agent prompt

Paste this into a coding agent (Claude Code, Cursor, Codex, …) to make the three changes across the whole project:

Migrate this project from the OpenAI API to AnyRouter.

1. Change the OpenAI client base URL to https://anyrouter.dev/api/v1
2. Swap OPENAI_API_KEY for ANYROUTER_API_KEY (prefix sk-ar-). Never hardcode it.
3. Rewrite model ids to the provider/model form:
     gpt-4o-mini → openai/gpt-5.4-mini
     gpt-4o      → openai/gpt-5.4
   Keep openai/* ids, or pick any model from https://anyrouter.dev/models
4. chat.completions and responses calls stay unchanged — same request/response.
5. Keep streaming and error handling exactly as they are.
6. Add a smoke test that sends one short prompt and prints the reply.

Only swap the provider config — do not change UI or business logic.

Troubleshooting

Related

• Chat Completions API — request and response reference.
• Responses API — typed output items and tool calls.
• Smart Routing — failover and model aliases.