Anthropic Provider

Setup

Set your Anthropic API key:

export ANTHROPIC_API_KEY=sk-ant-...

llmist will automatically discover and use Anthropic.

Available Models

Model	Alias	Best For
claude-opus-4-5	opus	Complex reasoning, creative tasks
claude-sonnet-4-5	sonnet	Balanced performance (recommended)
claude-haiku-4-5	haiku	Fast, cost-effective tasks

Tip

Sonnet is the recommended default—it offers the best balance of capability and cost for most use cases.

Usage Examples

Basic

import { LLMist } from 'llmist';

const answer = await LLMist.createAgent()
  .withModel('sonnet')
  .askAndCollect('Write a haiku about TypeScript');

With System Prompt

import { LLMist } from 'llmist';

const answer = await LLMist.createAgent()
  .withModel('sonnet')
  .withSystem('You are a helpful coding assistant. Be concise.')
  .askAndCollect('How do I read a file in Node.js?');

Long Context

import { LLMist } from 'llmist';
import { readFileSync } from 'fs';

const codebase = readFileSync('src/main.ts', 'utf-8');

const answer = await LLMist.createAgent()
  .withModel('sonnet')
  .withSystem('You are a code reviewer.')
  .askAndCollect(`Review this code:\n\n${codebase}`);

Vision (Image Input)

Claude models support image input:

import { LLMist, imageFromBuffer } from 'llmist';
import { readFileSync } from 'fs';

const imageBuffer = readFileSync('diagram.png');

const answer = await LLMist.createAgent()
  .withModel('sonnet')
  .askWithImage(
    'Describe this diagram',
    imageFromBuffer(imageBuffer, 'image/png')
  )
  .askAndCollect();

Supported image formats: JPEG, PNG, GIF, WebP

Model Characteristics

Claude Opus 4.5 Most Capable

• Best for complex reasoning and creative tasks
• Highest quality outputs
• Higher latency and cost
• 200K context window

Claude Sonnet 4.5 Recommended

• Best balance of capability and speed
• Great for coding, analysis, and general tasks
• Good cost efficiency
• 200K context window

Claude Haiku 4.5 Fastest

• Fastest response times
• Lowest cost
• Good for simple tasks and high-volume use
• 200K context window

Configuration Options

import { LLMist, AnthropicMessagesProvider } from 'llmist';

const client = new LLMist({
  autoDiscoverProviders: false,
  adapters: [
    new AnthropicMessagesProvider({
      apiKey: process.env.ANTHROPIC_API_KEY,
      baseUrl: 'https://api.anthropic.com', // Custom endpoint
    }),
  ],
});

Best Practices

1. Use Sonnet as default - Best balance for most tasks
2. Reserve Opus for complex reasoning - When quality matters more than speed
3. Use Haiku for high-volume - Simple tasks, classification, summarization
4. Leverage long context - Claude handles 200K tokens well

Cost Tracking

for await (const event of agent.run()) {
  if (event.type === 'llm_call_complete') {
    console.log('Input tokens:', event.usage?.promptTokens);
    console.log('Output tokens:', event.usage?.completionTokens);
    console.log('Estimated cost:', event.cost);
  }
}