Deep Cogito raised a $43M Series A led by TQ Ventures, with Benchmark, Nexus Venture Partners, and Zscaler among participants, bringing total funding past $56M. The bet isn't on the next frontier model — it's on whether post-training itself can become a standalone, sellable business.
Three non-big-lab teams used different RL post-training strategies to produce benchmark dark horses in 2026: Ornith's self-improvement loop (GRPO), Nous Research's DataForge + Atropos execution-reward RL, and MiniMax's massive-scale RL across 200K real environments. Different strengths, but one shared proof point: post-training RL matters more than pretraining scale.
Lecture 8 explains how instruction tuning, preference data, and RLHF turn a pretrained model into an assistant, then derives DPO from winner–loser pairs. Every step converts human judgment into signal—and imports its biases.
Lecture 15 divides post-training into imitation and optimization. SFT extracts pretrained capabilities from instruction-response data; RLHF uses pairwise feedback to bridge demonstrations and preferences. PPO and DPO both inherit data bias, reward overoptimization, and mode collapse.
Units 08–12 turn a base model into an interactive system: pre-training establishes capability, post-training shapes behavior, and generation plus evaluation determine how outputs are used.