Musk says Grok 4.8 trails Claude Opus 5.5; Anthropic will pay SpaceX $3.1 billion a month from December
The Nov. 10 concession is a dated promise from inside SpaceX, whose biggest compute tenant, Anthropic, will pay about $3.1 billion a month from December. At 44 times forward earnings the stock is priced on that rent; Grok is the part not yet paid for.
Richard Tangthree-minute read
On Nov. 10, asked on X how Grok 4.8 compares with Claude Opus 5.5, Elon Musk answered: "Not as good 12. Opus 5.5 is a masterpiece 12. But Grok 5 should exceed Opus 5.5 and maybe that happens in 2 or 3 months." 12
That answer carries a date and an owner, and treating it as color undersells it. SpaceX−3.35% — SpaceX, down 3.35 percent today (SPCX), the company Musk owns and runs, rents computing power to AI labs, and Anthropic$350B — Anthropic, private, latest valuation $350B, the company behind Claude, is the biggest of them. That rental business is now just over half of SpaceX's revenue. 2
Grok 5 is aimed at last season's champion
Grok 4.8 has finished pretraining and sits in reinforcement learning, the phase where a model's answers are shaped by feedback and rewards, before a soft rollout to users of X's Bot subscription later this week. 1 To get there, xAI$200B — xAI, private, latest valuation $200B abandoned JAX and SGLang, the machine-learning and model-serving software it had been using, for a training and inference stack rewritten in C and C++. 1 Musk has published no benchmark scores for 4.8, and Grok trails far back on the public leaderboards. 1
Two or three months from Nov. 10 puts the promised pass in the first quarter of 2027. 2 Anthropic moved the target the day before Musk spoke: on Nov. 9 it shipped Claude Fable 5.2 and Mythos 5.2, which it calls its most powerful models, and cut their price 20%. 2 Opus 5.5 now costs half what Fable does, and Anthropic itself recommends it for most coding work. 3 Grok 5 is scheduled to pass a model its own maker has repositioned as the cheaper tier. 3
The promise sits inside the landlord
xAI was folded into SpaceX in February, and its numbers hide inside the Super Intelligence segment, alongside the Cursor coding tool SpaceX bought in August and the rental contracts (we mapped the arrangement yesterday). 4 The segment is now the company's largest, yet it earned only $431 million of operating profit last quarter, after stock pay tied to Cursor$30B — Cursor, private, latest valuation $30B. 5
About a tenth of SpaceX's compute trains Grok, and management wants that near half. 2 The two uses compete for the same machines, and Anthropic's contracts are set to run about $3.1 billion a month once the last capacity lands in December. 2 Either side can cancel on 90 days' notice, and every customer Grok wins from Claude is compute Anthropic would no longer need to rent. 2 Musk has said plainly that if compute becomes "plentiful and cheap, SpaceX revenue will drop." 2
SpaceX's capex has outrun its revenue in every quarter of 2026
The buildout bill came due before the rental revenue did
- Revenue
- Capex
Data
| Revenue | Capex | |
|---|---|---|
| Q1 '25 | $4.07B | $4.14B |
| Q2 '25 | $4.07B | $2.83B |
| Q3 '25 | $5.58B | $6.88B |
| Q4 '25 | — | — |
| Q1 '26 | $4.69B | $10.11B |
| Q2 '26 | $7.81B | $18.37B |
| Q3 '26 | $14.58B | $19.59B |
The option is not free to carry. SpaceX has spent more on plants and equipment than it collected in revenue in every quarter of this year. 6
Two dated tests, one falsifier
At 44 times forward earnings, a buyer of SPCX is paying for the rent, with Grok as the option on top. 5 The option has two dated tests: how 4.8 lands with Bot users this week, and first-quarter 2027 results, the first quarter in which a Grok 5 inside Musk's window could show up as model revenue rather than rent. 2
The falsifier sits outside xAI's control. Another Anthropic price cut, like the one on Nov. 9, moves the market toward the cheap-compute world where the rent shrinks. 2 Anthropic set its IPO price range the day Musk spoke, valuing it at up to $1.4 trillion, so both sides of this race are now priced in public markets. 1 What carries the stock today is the rent.
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