Building Production AI Agents with DeepSeek V4 API: A Complete 2026 Guide DeepSeek V4 dropped in April 2026 with a 1M token context window, native MCP support, and agentic coding benchmarks that beat GPT-4o. At a fraction of the API cost. Here's how to actually build agents with it. ⚠️ Migration Warning : The old deepseek-chat and deepseek-reasoner endpoints will be deprecated on July 24, 2026 . Migrate to deepseek-v4-pro and deepseek-v4-r1 now. What's New in DeepSeek V4 (Quick Recap) Feature DeepSeek V4 Pro DeepSeek V4 Flash Context Window 1M tokens 128K tokens Agentic Coding SOTA Fast Function Calling ✅ Native ✅ Native MCP Support ✅ ✅ Input Price $0.14/1M tokens $0.07/1M tokens Speed ~45 tok/s ~120 tok/s The V4 Pro model is the one you want for agents — the 1M context lets you pass your entire codebase, long conversation history, or thousands of tool call results without truncating.…