anth-local-dev-loop

name	anth-local-dev-loop
description	Configure a local development workflow for Anthropic Claude API projects. Use when setting up dev environment, configuring hot reload, or establishing a fast iteration cycle with the Messages API. Trigger with phrases like "anthropic local dev", "claude dev setup", "anthropic development workflow", "test claude locally".
allowed-tools	Read, Write, Edit, Bash(npm:*), Bash(pip:*), Grep
version	1.0.0
license	MIT
author	Jeremy Longshore <[e-mail]>
tags	["saas","ai","anthropic"]
compatible-with	claude-code

Anthropic Local Dev Loop

Overview

Set up a fast local development cycle for Claude API projects with environment management, request logging, cost tracking, and hot-reload.

Prerequisites

• Completed anth-install-auth setup
• Node.js 18+ or Python 3.8+
• .env file with ANTHROPIC_API_KEY

Instructions

Step 1: Project Structure

my-claude-app/
├── .env                  # ANTHROPIC_API_KEY=sk-ant-...
├── .env.example          # ANTHROPIC_API_KEY=your-key-here
├── .gitignore            # Include .env
├── src/
│   ├── client.ts         # Singleton client
│   ├── prompts/          # System prompts as files
│   └── tools/            # Tool definitions
├── tests/
│   └── mock-responses/   # Saved API responses for testing
└── scripts/
    └── dev.ts            # Dev runner with logging

Step 2: Singleton Client with Request Logging

// src/client.ts
import Anthropic from '@anthropic-ai/sdk';

let client: Anthropic | null = null;

export function getClient(): Anthropic {
  if (!client) {
    client = new Anthropic({
      apiKey: process.env.ANTHROPIC_API_KEY,
      maxRetries: 2,
      timeout: 30_000,
    });
  }
  return client;
}

// Development logger — tracks cost per request
export function logUsage(messageId: string, : { input_tokens: ; output_tokens:  }, : ) {
   : <, { : ; :  }> = {
    : { : , :  },
    : { : , :  },
    : { : , :  },
  };
   rates = pricing[model] || pricing[];
   cost = (usage. * rates. + usage. * rates.) / ;
  .();
}