Quickstart - Hopper

Hopper serves open-source speech and language models behind an OpenAI-compatible API at https://api.withhopper.com.

Get an API key

Create a key at withhopper.com/console/keys. The full sk_hopper_... key is shown once, at creation. Export it as HOPPER_API_KEY.

export HOPPER_API_KEY=sk_hopper_...

Make a chat completion

Point an OpenAI client at the Hopper base URL and pass the key as a bearer token.

import os

from openai import OpenAI

client = OpenAI(
    base_url="https://api.withhopper.com/v1",
    api_key=os.environ["HOPPER_API_KEY"],
)

response = client.chat.completions.create(
    model="gemma-4-31b",
    messages=[{"role": "user", "content": "Say hello in one sentence."}],
)
print(response.choices[0].message.content)

import OpenAI from "openai";

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

const response = await client.chat.completions.create({
  model: "gemma-4-31b",
  messages: [{ role: "user", content: "Say hello in one sentence." }],
});
console.log(response.choices[0].message.content);

curl https://api.withhopper.com/v1/chat/completions \
  -H "Authorization: Bearer $HOPPER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemma-4-31b",
    "messages": [{"role": "user", "content": "Say hello in one sentence."}]
  }'

Stream the response

Set stream: true to receive the response as Server-Sent Events of chat.completion.chunk objects.

stream = client.chat.completions.create(
    model="gemma-4-31b",
    messages=[{"role": "user", "content": "Count to five."}],
    stream=True,
)
for chunk in stream:
    print(chunk.choices[0].delta.content or "", end="", flush=True)

const stream = await client.chat.completions.create({
  model: "gemma-4-31b",
  messages: [{ role: "user", content: "Count to five." }],
  stream: true,
});
for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? "");
}

curl -N https://api.withhopper.com/v1/chat/completions \
  -H "Authorization: Bearer $HOPPER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemma-4-31b",
    "messages": [{"role": "user", "content": "Count to five."}],
    "stream": true
  }'

Next

Models — model ids, endpoints, prices, and credits
Chat completions — streaming, tool calling, context window
Text to speech — speech, voices, and voice cloning
Speech to text — batch and streaming transcription
Errors — error envelope and codes