xAI dumps JAX, rewrites full RL/inference stack in C/C++ as Grok 4.8 enters RL
ivan_bezdomny · x · 2026-11-11
Elon Musk announced xAI has dropped JAX/SGLang and rewritten its entire RL and inference stack from scratch in C/C++. Pre-training for Grok 4.8 is done after heavy SFT data cleanup; the model is now in RL with evals climbing, and a soft rollout to Bot users comes later this week. Musk says 4.8 will bear "no resemblance" to 4.7 and, while not incredible yet, "the foundations are built right." Reposter Patrick Toulme speculates xAI likely used an RSI loop — thousands of swarm agents working for a week — to generate the ISA/megakernel code, noting the key is a strong verification loop, and quips that the JAX vs PyTorch debate is now moot: "the latest casualty of AI progress is the AI framework itself."
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