---
title: "Works with Your Stack"
description: "Configure an OpenAI SDK client with the Gateway base URL and key, then use creator-prefixed model names without rewriting the rest of the request."
canonical_url: "https://vercel.com/academy/ai-gateway/existing-ai-stack"
md_url: "https://vercel.com/academy/ai-gateway/existing-ai-stack.md"
docset_id: "vercel-academy"
doc_version: "1.0"
last_updated: "2026-08-08T23:27:13.221Z"
content_type: "lesson"
course: "ai-gateway"
course_title: "Using AI Gateway in Production"
prerequisites:  []
---

<agent-instructions>
Vercel Academy — structured learning, not reference docs.
Lessons are sequenced.
Adapt commands to the human's actual environment (OS, package manager, shell, editor) — detect from project context or ask, don't assume.
The lesson shows one path; if the human's project diverges, adapt concepts to their setup.
Preserve the learning goal over literal steps.
Quizzes are pedagogical — engage, don't spoil.
Quiz answers are included for your reference.
</agent-instructions>

# Works with Your Stack

# Will AI Gateway Work with My Existing AI Stack?

Working code has seniority. Replacing a provider SDK before the application needs anything else creates risk without much payoff.

We will start with the client's base URL.

\*\*Note: Quick Answer\*\*

AI Gateway provides compatible endpoints for existing OpenAI and Anthropic clients. Set the Gateway base URL, use a Gateway key, and prefix the model name with its creator. Frameworks including LangChain, LlamaIndex, and Pydantic AI also expose Gateway integration settings.

## Outcome

Point an OpenAI SDK client at the Gateway and use it to call both OpenAI and Anthropic models.

## Fast Track

1. Install the existing client with `pnpm add openai`
2. Set `baseURL: "https://ai-gateway.vercel.sh/v1"` and `apiKey` to your Gateway key
3. Ask for `anthropic/claude-sonnet-4.6` and watch the OpenAI SDK serve Claude

## Hands-on exercise

The Taco Tuesday assistant already uses the OpenAI SDK. We will preserve its request shape and change the client configuration.

Requirements:

- A `scripts/existing-stack.ts` using the `openai` package, not `ai`
- Construct the client with the Gateway's base URL and your `AI_GATEWAY_API_KEY`
- First call: the model the app always used, as `openai/gpt-5.4-mini` (note the creator prefix; that's the one naming change)
- Second call, same client: `anthropic/claude-sonnet-4.6`

The OpenAI SDK sends an OpenAI-compatible request to the Gateway endpoint. The Gateway can route that request to Claude without changing the client interface.

## Try It

```bash
pnpm existing-stack
```

```
[openai/gpt-5.4-mini via OpenAI SDK]
Order up: two Al Pastor Meteors, one Agua Fresca. That'll be $12.00.

[anthropic/claude-sonnet-4.6 via the same OpenAI SDK]
Two Al Pastor Meteors and today's agua fresca coming up — $12.00 even.
```

The same client reached models from two providers. Both requests now pass through AI Gateway and appear in its request history.

Two issues you may encounter:

**`404` or "model not found" with the old model name.** Gateway model names include the creator prefix. Change `gpt-5.4-mini` to `openai/gpt-5.4-mini` and verify the current string in the model catalog.

**Your stack uses a framework rather than a provider SDK.** The same approach applies, although the configuration key varies. LangChain, LlamaIndex, LiteLLM, Mastra, and Pydantic AI have documented integrations; most use the framework's existing option for an OpenAI-compatible base URL. In Python, the equivalent option is typically `base_url`.

## Commit

```bash
git commit -m "feat(compat): point the legacy OpenAI SDK client at the gateway"
```

## Done-When

- [ ] The OpenAI SDK returns a completion through the Gateway with only baseURL/apiKey changed
- [ ] The same client served a Claude model
- [ ] Both requests show up in your Gateway dashboard usage
- [ ] You can name where your framework's base URL setting lives (if you have one)

## Solution

```ts filename="scripts/existing-stack.ts"
import OpenAI from "openai";

// The only migration: this constructor used to have no arguments.
const openai = new OpenAI({
  apiKey: process.env.AI_GATEWAY_API_KEY,
  baseURL: "https://ai-gateway.vercel.sh/v1",
});

const order =
  "Take this order and confirm it back with a total: two Al Pastor Meteors " +
  "($4.50 each) and one agua fresca ($3.00).";

for (const model of ["openai/gpt-5.4-mini", "anthropic/claude-sonnet-4.6"]) {
  const completion = await openai.chat.completions.create({
    model,
    messages: [{ role: "user", content: order }],
  });

  console.log(`[${model} via OpenAI SDK]`);
  console.log(completion.choices[0].message.content?.trim());
  console.log();
}
```

The existing client code remains in place and now sends requests to the Gateway URL.

## Related Questions

- [How do I migrate off the raw OpenAI SDK?](/ai-gateway/stay-reliable/migrate-from-openai-sdk)
- [How do I switch models without rewriting my app?](/ai-gateway/stay-reliable/switch-models)
- [Why use AI Gateway instead of calling providers directly?](/ai-gateway/stay-reliable/why-ai-gateway)


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