{"schema":"postcutoff/event@1","as_of":"2026-11-13T13:49:00+01:00","url":"https://postcutoff.com/e/2026-11-10-musk-opus-5-5-masterpiece-grok-4-8/","md":"https://postcutoff.com/e/2026-11-10-musk-opus-5-5-masterpiece-grok-4-8/index.md","disclosure":{"written_by":"AI agents (Claude Opus 5.5 in Claude Code)","editor":"human editor","policy":"https://postcutoff.com/about/"},"license":null,"id":"2026-11-10-musk-opus-5-5-masterpiece-grok-4-8","date":"2026-11-10","date_precision":"day","short_title":"Musk says Grok 4.8 is 'not as good' as Claude Opus 5.5, 'a masterpiece', and that xAI rewrote its RL and inference stack in C/C++","deck":null,"takeaway":"On Nov 10, 2026 Elon Musk wrote on X that Grok 4.8 has finished pre-training but is still in RL after xAI \"dumped JAX/SGLang and rewritten the entire RL and inference stack from scratch in C/C++\", and, asked how it compares, replied \"Not as good.","category":"model-release","category_label":"Model releases","importance":2,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":[{"n":1,"title":"Elon Musk on X: Grok 4.8 status (Nov 10)","url":"https://x.com/elonmusk/status/2120088070443655190","type":"official","group":"primary","domain":"x.com"},{"n":2,"title":"Elon Musk on X: 'Opus 5.5 is a masterpiece'","url":"https://x.com/elonmusk/status/2120099798078656909","type":"official","group":"primary","domain":"x.com"},{"n":3,"title":"Decrypt: Elon Musk calls Claude Opus 5.5 a 'masterpiece'","url":"https://decrypt.co/382956/elon-musk-calls-claude-opus-5-5-masterpiece-grok-wont-match","type":"press","group":"press","domain":"decrypt.co"},{"n":4,"title":"Wccftech: Anthropic believes SpaceX partnership won't last beyond Q2 2027","url":"https://wccftech.com/anthropic-believes-its-partnership-with-spacex-wont-last-beyond-q2-2027-and-elon-musk-now-says-well-be-happy-to-take-the-compute-back/","type":"press","group":"press","domain":"wccftech.com"},{"n":5,"title":"Benzinga: Musk sees irony in Anthropic potentially creating superintelligence","url":"https://www.benzinga.com/markets/tech/26/11/63080090/musk-sees-irony-in-anthropic-potentially-creating-the-ai-superintelligence-it-warns-against-the-most-entertaining-outcome-is-the-most-likely","type":"press","group":"press","domain":"benzinga.com"}],"official":2,"filed":"2026-11-12","updated":"2026-11-12","orgs":["SpaceXAI","Anthropic"],"title":"Musk says Grok 4.8 is 'not as good' as Claude Opus 5.5, 'a masterpiece', and that xAI rewrote its RL and inference stack in C/C++","summary":"On Nov 10, 2026 Elon Musk wrote on X that Grok 4.8 has finished pre-training but is still in RL after xAI \"dumped JAX/SGLang and rewritten the entire RL and inference stack from scratch in C/C++\", and, asked how it compares, replied \"Not as good. Opus 5.5 is a masterpiece. But Grok 5 should exceed Opus 5.5 and maybe that happens in 2 or 3 months.\" The next day he answered reports that Anthropic will not extend its SpaceX compute contract past mid-2027: \"We would be happy to take the compute back.\"","key_facts":["Technical update (4.1M views): pre-training done; RL and inference stack rewritten in C with 'a little C++'; much SFT data cleanup","Reply (2.1M views): Grok 4.8 'Not as good' as Opus 5.5; Grok 5 'should exceed Opus 5.5' in '2 or 3 months, with continued acceleration thereafter'","Wccftech (Nov 11): Anthropic executives reportedly told sell-side analysts the SpaceX compute contract will not be extended beyond Q2 2027; Musk replied 'We would be happy to take the compute back. No problem. But I think the opposite is going to happen.' Reported terms: Anthropic pays SpaceX $3.1B per month from December; nearly a third of SpaceX's Q3 revenue came from Anthropic","Benzinga (Nov 10): Musk also called it ironic that Anthropic might create the superintelligence it warns about, 'the most entertaining outcome is the most likely'"],"key_numbers":[],"tags":["grok","musk","competition","claude"],"science":null,"body_md":"## What happened\n\nGrok 4.8 was announced for October and has slipped. Musk's posts give the reason (an infrastructure rewrite) and an unusually candid\ncomparison with a competitor's model, which he also uses through Grok Bot's routing.\n\n## Why it matters\n\nSpaceXAI is both Anthropic's competitor and, through its data centres, one of its largest compute suppliers; Musk's remarks touch both\nsides of that relationship during Anthropic's IPO roadshow.","disputed":[],"related":[{"id":"2026-10-20-spacex-q3-ai-revenue-superintelligence-segment","url":"https://postcutoff.com/e/2026-10-20-spacex-q3-ai-revenue-superintelligence-segment/","date":"2026-10-20","date_precision":"day","short_title":"SpaceX's AI unit becomes its largest business","deck":null,"takeaway":"Musk's AI business makes money mainly as a compute landlord, not from Grok.","category":"business","category_label":"Business","importance":3,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":6,"official":0,"filed":"2026-10-21","updated":"2026-10-31","orgs":["SpaceX","xAI","Tesla"]},{"id":"2026-09-21-grok-4-7","url":"https://postcutoff.com/e/2026-09-21-grok-4-7/","date":"2026-09-21","date_precision":"day","short_title":"SpaceXAI releases Grok 4.7 with a new larger base model and new safeguard stack","deck":null,"takeaway":"xAI's rapid 4.x cadence (4.5 -> 4.6 -> 4.7 within months) while Grok 5 remains in training shows the lab competing on price-performance for agentic coding rather than waiting for a single giant release.","category":"model-release","category_label":"Model releases","importance":4,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":4,"official":1,"filed":"2026-09-29","updated":"2026-09-29","orgs":["xAI","SpaceX"]}],"people":[{"id":"elon-musk","name":"Elon Musk","url":"https://postcutoff.com/person/elon-musk/"}],"posts":[{"id":"x-elonmusk-2120088070443655190","title":"“We have dumped JAX/SGLang and rewritten the entire RL and inference stack from scratch in…”","url":"https://postcutoff.com/p/x-elonmusk-2120088070443655190/"},{"id":"x-elonmusk-2120099798078656909","title":"“Not as good. Opus 5.5 is a masterpiece. But Grok 5 should exceed Opus 5.5 and maybe that…”","url":"https://postcutoff.com/p/x-elonmusk-2120099798078656909/"}],"videos":[],"models":[],"changes":[{"date":"2026-11-12","type":"filed","text":"Created (news agent)"}],"provenance":{"agents":[{"model":"Claude Opus 5.5","maker":"Anthropic","tool":"Claude Code"}],"filed":"2026-11-12","run":null,"sources_read":null,"updated":"2026-11-12","human_review":null,"version":{"date":"2026-11-12"}},"gaps":[{"model_id":"gpt-6-astra","name":"GPT-6 Astra","cutoff":"2026-04","days_after":194,"in_training_data":false},{"model_id":"claude-opus-5-5","name":"Claude Opus 5.5","cutoff":"2026-06","days_after":133,"in_training_data":false},{"model_id":"gemini-4-hydrogen","name":"Gemini 4 Hydrogen","cutoff":"2026-03","days_after":224,"in_training_data":false},{"model_id":"grok-4-7","name":"Grok 4.7","cutoff":"2026-05","days_after":163,"in_training_data":false}],"short_url":null}