--- title: "Musk says Grok 4.8 trails Claude Opus 5.5; Anthropic will pay SpaceX $3.1 billion a month from December" description: "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." publisher: "The Inference" section: "Model" published: 2026-11-11T15:49:28.141Z modified: 2026-11-11T15:49:28.141Z canonical: https://theinference.org/article/musk-says-grok-4-8-trails-claude-opus-5-5-anthropic-will-pay-spacex-3-1-billion-a-month-from-december language: en keywords: "XAI, Anthropic, SpaceX, Grok, AI Compute, Claude" --- # 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. On Nov. 10, asked on X how Grok 4.8 compares with Claude Opus 5.5, [Elon Musk](https://theinference.org/markets/people/elon-musk) answered: "Not as good [1][2]. [Opus 5.5 is a masterpiece](https://decrypt.co/382956/elon-musk-calls-claude-opus-5-5-masterpiece-grok-wont-match) [1][2]. But Grok 5 should exceed Opus 5.5 and maybe that happens in 2 or 3 months." [1][2] That answer carries a date and an owner, and treating it as color undersells it. [SpaceX](https://theinference.org/markets/companies/spacex) (SPCX), the company Musk owns and runs, rents computing power to AI labs, and [Anthropic](https://theinference.org/markets/companies/anthropic), 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](https://theinference.org/markets/companies/xai) 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](https://venturebeat.com/technology/anthropic-releases-claude-fable-5-2-and-mythos-5-2-pairing-new-record-high-benchmarks-with-20-api-cost-reduction), 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](https://theinference.org/article/xai-s-grok-4-8-entered-training-57-days-late-with-no-price-card-anthropic-pays-spacex-1-25-billion-a-month)). [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](https://theinference.org/markets/companies/anysphere). [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 $3.1 billion a month once the last capacity lands in December. [2] Either side can [cancel on 90 days' notice](https://theinference.org/article/anthropic-can-walk-from-most-of-its-spacex-rent-on-90-days-notice-as-the-december-8-unlock-starts-below-135), and every customer Grok wins from Claude is compute Anthropic would no longer need to rent. [2] Musk has said plainly that if compute becomes "plentiful and cheap, SpaceX revenue will drop." [2] *Chart: **SpaceX's capex has outrun its revenue in every quarter of 2026** Line chart of SpaceX quarterly revenue and capital spending from Q1 2025 to Q3 2026, with capex above revenue in all of 2026* *Reported quarterly revenue and capital spending, US$ billions; Q4 2025 not on file. Source: SpaceX SEC filings. [5][6]* 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](https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0001181412). [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](https://finance.yahoo.com/technology/ai/articles/musk-calls-anthropic-opus-5-175532896.html), 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. ## Takeaway Musk's Nov. 10 concession sets a dated test: if Grok 5 does not pass Claude Opus 5.5 in two or three months, SPCX at 44 times forward earnings is priced on Anthropic's $3.1 billion a month rent alone, and Anthropic can walk from it on 90 days' notice. ## Sources 1. [Decrypt, "Elon Musk Calls Claude Opus 5.5 a 'Masterpiece', Admits Grok 4.8 Won't Match It," Nov. 10, 2026](https://decrypt.co/382956/elon-musk-calls-claude-opus-5-5-masterpiece-grok-wont-match) 2. [Yahoo Finance, "Musk Calls Anthropic's Opus 5.5 'a Masterpiece' but Says Grok 5 Beats It 'in 2 or 3 Months'," Nov. 10, 2026](https://finance.yahoo.com/technology/ai/articles/musk-calls-anthropic-opus-5-175532896.html) 3. [VentureBeat, "Anthropic releases Claude Fable 5.2 and Mythos 5.2, pairing new, record-high benchmarks with 20% API cost reduction," Nov. 9, 2026](https://venturebeat.com/technology/anthropic-releases-claude-fable-5-2-and-mythos-5-2-pairing-new-record-high-benchmarks-with-20-api-cost-reduction) 4. [IFCM Tanzania, "xAI Leeching off SpaceX," Nov. 6, 2026](https://www.ifcmtz.com/en/trading-news/stocks/spcx/xai-leeching-off-spacex-2026-11-06) 5. [Yahoo Finance, "SpaceX's AI Business Now Outsells Starlink, as Starlink's Revenue per User Falls to $69 From $83," Nov. 10, 2026](https://finance.yahoo.com/technology/ai/articles/spacex-ai-business-now-outsells-160800288.html) 6. [SpaceX, quarterly figures from its SEC filings, retrieved 11 November 2026](https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0001181412) --- Musk says Grok 4.8 trails Claude Opus 5.5; Anthropic will pay SpaceX $3.1 billion a month from December — The Inference. Canonical: https://theinference.org/article/musk-says-grok-4-8-trails-claude-opus-5-5-anthropic-will-pay-spacex-3-1-billion-a-month-from-december