Cerebras — Wafer-Scale LLM Inference

Overview

Cerebras Inference, the ultra-fast LLM inference service powered by the world's largest chip (Wafer-Scale Engine). Helps developers integrate Cerebras' API for applications requiring the fastest possible token generation — real-time chat, code completion, and interactive AI experiences.

Instructions

Chat Completions

// src/llm/cerebras.ts — Cerebras API (OpenAI-compatible)
import OpenAI from "openai";

const cerebras = new OpenAI({
  apiKey: process.env.CEREBRAS_API_KEY!,
  baseURL: "https://api.cerebras.ai/v1",
});

// Basic completion — up to 2000+ tokens/second
async function chat(prompt: string) {
  const response = await cerebras.chat.completions.create({
    model: "llama3.3-70b",                // Llama 3.3 70B on Cerebras hardware
    messages: [
      { role: "system", content: "You are a helpful coding assistant." },
      { role: "user", content: prompt },
    ],
    temperature: 0.7,
    max_tokens: 1024,
    top_p: 1,
  });

  // Response includes usage with Cerebras-specific speed metrics
  console.log(`Tokens/sec: ${response.usage?.completion_tokens! / (response.usage as any).completion_time}`);

  return response.choices[0].message.content;
}

// Streaming — first token in <200ms
async function streamChat(prompt: string, onChunk: (text: string) => void) {
  const stream = await cerebras.chat.completions.create({
    model: "llama3.3-70b",
    messages: [{ role: "user", content: prompt }],
    stream: true,
  });

  let full = "";
  for await (const chunk of stream) {
    const text = chunk.choices[0]?.delta?.content ?? "";
    full += text;
    onChunk(text);
  }
  return full;
}

// JSON mode
async function structuredOutput(prompt: string) {
  const response = await cerebras.chat.completions.create({
    model: "llama3.3-70b",
    messages: [{ role: "user", content: prompt }],
    response_format: { type: "json_object" },
    temperature: 0,
  });
  return JSON.parse(response.choices[0].message.content!);
}

Tool Use / Function Calling

async function chatWithTools(prompt: string) {
  const response = await cerebras.chat.completions.create({
    model: "llama3.3-70b",
    messages: [{ role: "user", content: prompt }],
    tools: [
      {
        type: "function",
        function: {
          name: "get_stock_price",
          description: "Get the current stock price for a ticker symbol",
          parameters: {
            type: "object",
            properties: {
              ticker: { type: "string", description: "Stock ticker (e.g., AAPL)" },
            },
            required: ["ticker"],
          },
        },
      },
    ],
    tool_choice: "auto",
  });

  const msg = response.choices[0].message;
  if (msg.tool_calls) {
    // Execute the tool and send results back
    const toolResults = await Promise.all(
      msg.tool_calls.map(async (call) => {
        const args = JSON.parse(call.function.arguments);
        const result = await executeFunction(call.function.name, args);
        return {
          role: "tool" as const,
          tool_call_id: call.id,
          content: JSON.stringify(result),
        };
      })
    );

    // Get final response with tool results
    const final = await cerebras.chat.completions.create({
      model: "llama3.3-70b",
      messages: [
        { role: "user", content: prompt },
        msg,
        ...toolResults,
      ],
    });
    return final.choices[0].message.content;
  }

  return msg.content;
}

Python Integration

# src/cerebras_client.py — Cerebras with Python
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["CEREBRAS_API_KEY"],
    base_url="https://api.cerebras.ai/v1",
)

# Chat completion
response = client.chat.completions.create(
    model="llama3.3-70b",
    messages=[{"role": "user", "content": "Write a Python quicksort implementation"}],
    temperature=0.3,
    max_tokens=500,
)
print(response.choices[0].message.content)

# Streaming
stream = client.chat.completions.create(
    model="llama3.3-70b",
    messages=[{"role": "user", "content": "Explain transformers in 5 sentences"}],
    stream=True,
)
for chunk in stream:
    print(chunk.choices[0].delta.content or "", end="", flush=True)

Available Models

## Cerebras Models
- **llama3.3-70b** — Llama 3.3 70B, best quality, ~2000 tok/s output
- **llama3.1-8b** — Llama 3.1 8B, fastest option, ~2500+ tok/s output
- **llama3.1-70b** — Llama 3.1 70B, large context (128K tokens)

## Speed Comparison (approximate)
- Cerebras: 2000+ tok/s (70B model)
- Groq: 300-400 tok/s (70B model)
- Cloud GPU (A100): 50-80 tok/s (70B model)
- Local (M3 Max): 20-40 tok/s (70B quantized)

Installation

# Use any OpenAI-compatible SDK
npm install openai
pip install openai

# Set base_url to https://api.cerebras.ai/v1

Examples

Example 1: Setting up an evaluation pipeline for a RAG application

User request:

I have a RAG chatbot that answers questions from our docs. Set up Cerebras to evaluate answer quality.

The agent creates an evaluation suite with appropriate metrics (faithfulness, relevance, answer correctness), configures test datasets from real user questions, runs baseline evaluations, and sets up CI integration so evaluations run on every prompt or retrieval change.

Example 2: Comparing model performance across prompts

User request:

We're testing GPT-4o vs Claude on our customer support prompts. Set up a comparison with Cerebras.

The agent creates a structured experiment with the existing prompt set, configures both model providers, defines scoring criteria specific to customer support (accuracy, tone, completeness), runs the comparison, and generates a summary report with statistical significance indicators.

Guidelines

1. Use for latency-critical applications — Cerebras is the fastest inference available; ideal for real-time chat and autocomplete
2. OpenAI SDK drop-in — Change base URL from OpenAI to Cerebras; your code works unchanged
3. 8B for simple tasks — Use llama3.1-8b for classification, extraction, and simple Q&A; save 70B for complex reasoning
4. Stream everything — First-token latency is <200ms; streaming gives users instant feedback
5. JSON mode for structured output — Use response_format: { type: "json_object" } for reliable parsing
6. Batch simple requests — For bulk processing, send multiple independent prompts in parallel
7. Monitor rate limits — Free tier has request limits; check headers for remaining quota
8. Fallback strategy — Have a fallback to Groq or OpenAI; Cerebras can have capacity constraints during high demand