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DeepSeek's API is broadly compatible with the OpenAI SDK, requiring only three configuration changes: the baseURL, apiKey, and model name string. This tutorial covers setting up a provider-agnostic AI client, implementing token-by-token streaming via Server-Sent Events, and building a full-stack React + Node.js/Express chat application backed by DeepSeek. It also includes production-ready error handling with exponential backoff for rate limits, input validation, CORS configuration, and a deployment checklist. The two primary DeepSeek models covered are deepseek-chat (general-purpose) and deepseek-reasoner (chain-of-thought reasoning).