Musk: xAI rebuilt Grok's RL training and inference stack from scratch in C, with Starlink engineers
elonmusk · x · 2026-11-10
Elon Musk revealed that xAI's new Grok training and inference infrastructure was rewritten from scratch by SpaceXSI, replacing JAX and SGLang with a custom stack built primarily in C (with some C++).
The engineering team behind it comes from the people who built Starlink's satellite network software. Musk highlighted SpaceX's culture of full control over its own software—writing its own headers and handling leap-second time calculations—as the foundation now powering Grok's AI infrastructure.
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