# SDKs and frameworks

> Use the official OpenAI and Anthropic SDKs, LangChain, the Vercel AI SDK and LiteLLM with the gateway. The base URL and key settings for each, with working code.

Source: https://oneaiapikey.com/docs/sdks

Any library that lets you set a base URL for the OpenAI or Anthropic API works with the gateway. You change two settings: the **base URL** and the **API key**. Everything else (request shapes, streaming, tools, errors) stays as the library documents it.

OpenAI SDKs `https://api.oneaiapikey.com/v1`

Anthropic SDKs `https://api.oneaiapikey.com`

> **The one difference to remember:** OpenAI-format clients take the base URL **with** `/v1`. Anthropic SDKs take it **without** `/v1`, because they add `/v1/messages` themselves. The Vercel AI SDK’s Anthropic provider is the exception: it expects `/v1`.

## OpenAI SDK

Works with every model, in the [chat completions](https://oneaiapikey.com/docs/chat-completions) format. The SDK also reads `OPENAI_BASE_URL` and `OPENAI_API_KEY` from the environment if you prefer not to pass them in code.

Python:

```python
# pip install openai
import os
from openai import OpenAI

client = OpenAI(base_url="https://api.oneaiapikey.com/v1", api_key=os.environ["RELAYKIT_API_KEY"])
reply = client.chat.completions.create(
    model="claude-haiku-4-5",
    messages=[{"role": "user", "content": "Say hello in five words."}],
)
print(reply.choices[0].message.content)
```

Node:

```js
// npm install openai
import OpenAI from "openai";

const client = new OpenAI({ baseURL: "https://api.oneaiapikey.com/v1", apiKey: process.env.RELAYKIT_API_KEY });
const reply = await client.chat.completions.create({
  model: "claude-haiku-4-5",
  messages: [{ role: "user", content: "Say hello in five words." }],
});
console.log(reply.choices[0].message.content);
```

## Anthropic SDK

For Claude models in Anthropic’s own format, with [prompt caching](https://oneaiapikey.com/docs/prompt-caching), extended thinking and every Messages feature. It also reads `ANTHROPIC_BASE_URL` and `ANTHROPIC_API_KEY`.

Python:

```python
# pip install anthropic
import os
import anthropic

client = anthropic.Anthropic(base_url="https://api.oneaiapikey.com", api_key=os.environ["RELAYKIT_API_KEY"])
message = client.messages.create(
    model="claude-sonnet-5-5",
    max_tokens=512,
    messages=[{"role": "user", "content": "Say hello in five words."}],
)
print(message.content[0].text)
```

Node:

```js
// npm install @anthropic-ai/sdk
import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({ baseURL: "https://api.oneaiapikey.com", apiKey: process.env.RELAYKIT_API_KEY });
const message = await client.messages.create({
  model: "claude-sonnet-5-5",
  max_tokens: 512,
  messages: [{ role: "user", content: "Say hello in five words." }],
});
console.log(message.content[0].text);
```

## LangChain

`ChatOpenAI` works with every model; `ChatAnthropic` with Claude models. Leave `use_responses_api` off on `ChatOpenAI` unless the model is a GPT model, because the [Responses API](https://oneaiapikey.com/docs/responses) is fully supported only there.

Python:

```python
# pip install langchain-openai langchain-anthropic
import os
from langchain_openai import ChatOpenAI
from langchain_anthropic import ChatAnthropic

llm = ChatOpenAI(
    model="gpt-5.6-terra",
    base_url="https://api.oneaiapikey.com/v1",
    api_key=os.environ["RELAYKIT_API_KEY"],
)
print(llm.invoke("Say hello in five words.").content)

claude = ChatAnthropic(
    model="claude-sonnet-5-5",
    base_url="https://api.oneaiapikey.com",   # no /v1
    api_key=os.environ["RELAYKIT_API_KEY"],
)
```

JS:

```js
// npm install @langchain/openai
import { ChatOpenAI } from "@langchain/openai";

const llm = new ChatOpenAI({
  model: "gpt-5.6-terra",
  apiKey: process.env.RELAYKIT_API_KEY,
  configuration: { baseURL: "https://api.oneaiapikey.com/v1" },
});
const reply = await llm.invoke("Say hello in five words.");
console.log(reply.content);
```

## Vercel AI SDK

Use the OpenAI-compatible provider for any model. The plain `@ai-sdk/openai` provider also works, but `openai("id")` calls the Responses API; use `openai.chat("id")` to send chat completions instead.

AI SDK:

```ts
// npm install ai @ai-sdk/openai-compatible @ai-sdk/anthropic
import { generateText, streamText } from "ai";
import { createOpenAICompatible } from "@ai-sdk/openai-compatible";
import { createAnthropic } from "@ai-sdk/anthropic";

// Any model, OpenAI format (chat completions)
const gateway = createOpenAICompatible({
  name: "gateway",
  baseURL: "https://api.oneaiapikey.com/v1",
  apiKey: process.env.RELAYKIT_API_KEY,
  includeUsage: true,          // token counts on streamed responses
});

const { text } = await generateText({
  model: gateway("claude-haiku-4-5"),
  prompt: "Say hello in five words.",
});

// Claude models, Anthropic format. This provider expects /v1 in the base URL.
const anthropic = createAnthropic({
  baseURL: "https://api.oneaiapikey.com/v1",
  apiKey: process.env.RELAYKIT_API_KEY,
});

const result = streamText({ model: anthropic("claude-sonnet-5-5"), prompt: "Write a haiku about latency." });
for await (const chunk of result.textStream) process.stdout.write(chunk);
```

## LiteLLM

Prefix the model id with `openai/` and set `api_base` to the OpenAI base URL.

LiteLLM SDK:

```python
# pip install litellm
import os
from litellm import completion

reply = completion(
    model="openai/claude-haiku-4-5",              # "openai/" tells LiteLLM to use the OpenAI format
    api_base="https://api.oneaiapikey.com/v1",
    api_key=os.environ["RELAYKIT_API_KEY"],
    messages=[{"role": "user", "content": "Say hello in five words."}],
)
print(reply.choices[0].message.content)
```

The same settings work in the LiteLLM proxy:

LiteLLM proxy:

```yaml
# config.yaml for the LiteLLM proxy
model_list:
  - model_name: claude-haiku-4-5
    litellm_params:
      model: openai/claude-haiku-4-5
      api_base: https://api.oneaiapikey.com/v1
      api_key: os.environ/RELAYKIT_API_KEY
```

## Other languages

Libraries for Go, Java, .NET, Ruby, Rust and PHP that target the OpenAI API usually have a base URL or endpoint option. Set it to the OpenAI base URL above and pass your key as the API key. With plain HTTP, send `Authorization: Bearer <key>` to `POST https://api.oneaiapikey.com/v1/chat/completions`; the [API reference](https://oneaiapikey.com/docs/api-reference) lists every endpoint.

## Chat apps and coding tools

- Chat apps: [Open WebUI](https://oneaiapikey.com/docs/apps/open-webui), [LibreChat](https://oneaiapikey.com/docs/apps/librechat), [LobeChat](https://oneaiapikey.com/docs/apps/lobechat), [SillyTavern](https://oneaiapikey.com/docs/apps/sillytavern), [Chatbox](https://oneaiapikey.com/docs/apps/chatbox).
- Coding agents and editors: see the [coding tools overview](https://oneaiapikey.com/docs/guides).