Xai named grok 4.8, a 2.5-trillion-parameter c++ rewrite, on sept 13 while grok 4.7 still has no…
xai named grok 4.8, a 2.5-trillion-parameter c++ rewrite, on sept 13 while grok 4.7 still has no model page, api id or price after five missed launch dates. the dev conversation now treats a roadmap like a release.
hype is moving faster than the model.
Context
Cellcog, a secondary source dated 14 September 2026, says Musk wrote on 13 September that Grok 4.8 is a 2.5T model trained with a new C++ software stack, and that xAI's own pages contained no Grok 4.8 as of 14 September. RuntimeWire says Musk claimed the 2.5T run beat a 2.1T JAX-trained run, with no evaluations given. xAI's own post of 21 September 2026 introduces Grok 4.7, served at the same price and speed as Grok 4.6.
The name and the 2.5T come from Musk's X post as relayed by secondary outlets, and the post itself was not read, so it is a relayed personal post and not a release, and no xAI model page for Grok 4.8 was read. Secondary reports describe a new C++ training stack, not a rewrite of the model, and 2.5T is not defined as total or active parameters. The Grok 4.7 gap closed the day after the note: xAI's post is dated 21 September, though the docs pricing table fetched still lacked a grok-4.7 row, which was not reconciled. The five missed launch dates is a secondary count only.
Watch next
- An xAI model page or API id for Grok 4.8 and a definition of 2.5T.
Sources
Provenance
The note above is reproduced unedited from the original post, first published on Threads on 20 September 2026 at 01:49 IST. Sources are the papers and datasets the note draws on.
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