SpaceXSI · Grok · 10 Nov 2026
Grok 4.8 is in RL on a homemade C stack, with a soft Bot rollout pledged later this week (as of 10 Nov 2026)
Elon Musk said early on 10 Nov 2026 that SpaceXSI has replaced the open-source JAX and SGLang tools with its own C/C++ code for reinforcement learning and inference, and that Grok 4.8 has finished pre-training and is now in RL. He said the company “will do a soft rollout to Bot users later this week and see how it goes.” That is a plan, not a confirmed release: no date, cohort size, benchmarks or pricing came with it.
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The editor holds Tesla and SpaceX shares. Supercharged Daily is independent and not affiliated with either company. Nothing here is financial advice.
Update, 11 Nov 2026: Claroc says 94.7% of the live Grok Build apps it tried opened without sign-in as of 10 Nov 2026, including 24 built by SpaceXSI staff. That is a report, not a proven breach. What Claroc reported →
What Musk said
At 4:35 a.m. ET (1:35 a.m. PT) on 10 Nov 2026, answering a user who asked when to expect Grok 4.8, Musk wrote that SpaceXSI had “dumped JAX/SGLang” and rewritten “the entire RL and inference stack from scratch in C/C++, which took some extra time.” Pre-training is done, he said, and “4.8 is in RL and the evals are starting to climb.” He also wrote that 4.8 “will bear no resemblance to 4.7 (thankfully)” and that “it is not yet incredible, but, this time, the foundations are built right.”
We have dumped JAX/SGLang and rewritten the entire RL and inference stack from scratch in C/C++, which took some extra time.
— Elon Musk (@elonmusk) November 10, 2026
Training (aka pre-training) is done. Lot of cleanup was needed on the SFT data to get that mostly right. Now, 4.8 is in RL and the evals are starting to climb. We will do a soft rollout to Bot users later this week and see how it goes.
Grok 4.8 will bear no resemblance to 4.7 (thankfully). It is not yet incredible, but, this time, the foundations are built right, so I expect it to evolve to be something special.
Post: Elon Musk (@elonmusk), 4:35 a.m. ET on 10 Nov 2026 (1:35 a.m. PT), replying to a user asking for a Grok 4.8 update. Embedded from X via x-embed.js. The blockquote is the full post text.
58 days from “start RL” to “in RL”
On 13 Sep 2026 at 9:24 p.m. ET (6:24 p.m. PT), Musk said Grok 4.8, “a 2.5T model trained with our new C++ software stack, will finish training this week and start RL.” The 10 Nov post came 58 days later, counting in Eastern Time, and still has 4.8 in RL. He gave two reasons the work took extra time: the rewrite, and the SFT data, which needed a “lot of cleanup.” The 2.5T figure is from that September post only; SpaceXSI has not published a parameter count.
The rewrite was already on his list. The next morning, 14 Sep 2026, he wrote that pre-training ran on in-house C/C++ code “written primarily by the Starlink software team,” while RL still ran on “a legacy pile of many different third-party software systems.” Meanwhile Grok 4.7 launched on 21 Sep 2026, 50 days before this 10 Nov update.
What gets replaced
JAX is an open-source Python library for accelerator-oriented array computation and large-scale machine learning. SGLang is an open-source serving framework for large language models. xAI’s original Grok announcement said its training and inference stack was built on Kubernetes, Rust and JAX. Musk now says the new code is “C with a little C++, but not too much,” has “some assembly,” and is derived from work done to create Starlink. At 5:34 a.m. ET (2:34 a.m. PT) he added that Starlink software is “very well suited to training super intelligence.” Those stack claims are Musk’s words. As of 10 Nov 2026, SpaceXSI’s news page has no Grok 4.8 post, and no official code or speed figures for the new stack were published with these posts.
What “soft rollout” means for Bot users
It is a pledge of a test, not a confirmed place in a queue. Musk gave no day beyond “later this week,” no group size, no benchmarks and no API name or price. Grok 4.7’s launch page lists $2 per million input tokens and $6 per million output tokens, and 4.8 has no page yet. Capacity is a live issue too. On 1 Nov 2026 Musk said the cost of serving Grok Bot “was unsustainably high relative to revenue” (our report). Until SpaceXSI posts 4.8 on its news page, treat this week’s rollout as a plan.
— Alex R
Sources: Elon Musk on X (10 Nov 2026); Musk replies on X, 10 Nov 2026: 1, 2, 3, 4; Musk on X (1 Nov 2026); Musk on X (13 Sep 2026, ET); Musk on X (14 Sep 2026); SpaceXSI: Introducing Grok 4.7 (21 Sep 2026); xAI: Announcing Grok; SpaceXSI news index (checked 10 Nov 2026); JAX docs; SGLang on GitHub. Related: Grok Bot users hit their weekly limits days early. Hero photo: 极客湾Geekerwan / Wikimedia Commons, CC BY 3.0. Never Electrek.
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