Claude Architecture Variants

Overview

Five architecture patterns for Claude-powered applications: Chatbot (stateless API wrapper), RAG (retrieval-augmented generation with vector search), Agent (tool use loop), Content Pipeline (batch processing), and Evaluation (using Claude as a judge). Each includes complete code and a comparison table.

1. Chatbot (Stateless API Wrapper)

Simplest pattern — proxy Claude with a system prompt.

// api/chat.ts
export async function POST(req: Request) {
  const { messages } = await req.json();
  const response = await client.messages.create({
    model: 'claude-sonnet-4-20250514',
    max_tokens: 2048,
    system: 'You are a helpful assistant for our SaaS product.',
    messages,
    stream: true,
  });
  return new Response(response.toReadableStream());
}

Best for: Customer support, Q&A, simple conversational interfaces.

2. RAG (Retrieval-Augmented Generation)

Fetch relevant context, inject into prompt, generate grounded answer.

async function ragQuery(question: string) {
  // 1. Embed the question (use Voyage, OpenAI, or Cohere — not Anthropic)
  const embedding = await embeddingClient.embed(question);

  // 2. Search vector DB for relevant chunks
  const chunks = await vectorDb.query(embedding, { topK: 5 });

  // 3. Send to Claude with context
  const message = await client.messages.create({
    model: 'claude-sonnet-4-20250514',
    max_tokens: 2048,
    system: `Answer based on the provided context. If the context doesn't contain the answer, say so.`,
    messages: [{
      role: 'user',
      content: `Context:\n${chunks.map(c => c.text).join('\n---\n')}\n\nQuestion: ${question}`,
    }],
  });
  return message.content[0].text;
}

Best for: Documentation Q&A, knowledge bases, support with source citations.

3. Agent (Tool Use Loop)

Claude decides which tools to call, you execute them, loop until done.

async function agentLoop(userInput: string, tools: Anthropic.Tool[]) {
  let messages: MessageParam[] = [{ role: 'user', content: userInput }];

  while (true) {
    const response = await client.messages.create({
      model: 'claude-sonnet-4-20250514',
      max_tokens: 4096,
      tools,
      messages,
    });
    messages.push({ role: 'assistant', content: response.content });

    if (response.stop_reason === 'end_turn') {
      return response.content.find(b => b.type === 'text')?.text;
    }

    // Execute tools
    const results = [];
    for (const block of response.content) {
      if (block.type === 'tool_use') {
        const result = await executeTool(block.name, block.input);
        results.push({ type: 'tool_result', tool_use_id: block.id, content: JSON.stringify(result) });
      }
    }
    messages.push({ role: 'user', content: results });
  }
}