Grok 4.8 shows up in xAI's own code: its public coding agent already lists it

xAI's public grok-build repository, the source of its Grok Build coding agent, now lists grok-4.8 by name. The model picker registers "grok-4.8" as "Grok 4.8", and the router tests route to it with 500K and 256K context windows. We read the code on GitHub on September 29; the repo was last updated that evening.

WHAT IS SOURCED

The id and the name are in xAI's own code, which is stronger than a screenshot or a leaker's word. The context windows are test fixtures, not a spec sheet, so treat them as what xAI's tests assume rather than what the model will ship with. A separate report, from a single account, says Cursor's server-side model list already carries grok-4.8-high, grok-4.8-high-fast and grok-4.8-xhigh-fast; we have not seen that list ourselves.

WHAT WE DO NOT KNOW

No date, no price and no benchmark. xAI has not announced it; the only public word before this was Elon Musk describing a roughly 2.5T-parameter model on a new C++ stack. Grok 4.7 shipped on September 21, and xAI's recent cadence has been five to six weeks.

Grok 4.8 is armed on our radar, and every id shape above fires it.