SITUATION EXPLAINED: DeepSeek just open-sourced the engine that runs its AI, something OpenAI and Anthropic haven't done. • DeepInfer powers DeepSeek V4.1 Flash, which costs $0.30 per million input tokens and $1.20 per million output, and it's now open source under Apache 2.0 • Inference is running a trained model, and serving a 552B-parameter one fast and cheap to millions of users is one of AI's hardest engineering problems • It spreads users, long prompts, and expert sub-networks across…