Report: Anthropic Trained Mythos 2 but Shelved It, Pivoting to Mythos 3
SemiAnalysis founder and analyst Dylan Patel, in an internal podcast conversation with Jordan Nanos, revealed an unconfirmed claim: Anthropic's next-generation model Mythos 2 has completed all training, but the company has decided not to release it and is instead going straight into Mythos 3 development. Patel said the current focus is internal improvement, with no clear timeline for a new public release. The claim circulated via X users @kimmonismus, @Neurogence and Reddit with consistent retellings.
Confirmed
- The claim originates from SemiAnalysis analyst Dylan Patel and was relayed by multiple outlets, but remains a single-source leak
- Reportedly Mythos 2 training is complete with no release plan, while the internal build loop for Mythos 3 continues
Unconfirmed
- @Neurogence stressed the information is unverified; Anthropic has made no official response
- @新智元 relayed that Mythos 2 was shelved after triggering an internal top-level alert for being too capable (code generation, logical reasoning, and cyber-offense capabilities) — a motive detail found only in one retelling
- @haider1 cited another report claiming Anthropic's internal models (tentatively Mythos 2/5.1) underperformed: Model 1 merely matched Mythos 5 and Model 2 showed only modest gains — in tension with the 'too capable to ship' narrative
Why it matters
- If true, Anthropic has changed its release cadence, stockpiling a strong model to iterate on the next generation rather than shipping it, which would reshape the frontier-model race against OpenAI and Google
- Contradictory accounts of why the model was shelved (too strong vs. underwhelming) show how uncertain outside speculation about Anthropic's progress remains
2026-08-18 ~ 2026-08-19 · 5 related posts
Primary sources
- Anthropic Completes Mythos 2 Training But Declines Release; Mythos 3 Loop Active — kimmonismus · 2026-08-18
- Report: Anthropic Finished Training Mythos 2 But Won't Release It Yet — Neurogence · 2026-08-18
- [source] SemiAnalysis claims Anthropic's completed Mythos2 is shelved for safety, now used to train Mythos3 — 新智元 · 2026-08-18
- Anthropic's next Mythos model reportedly shows only modest improvement — haider1 · 2026-08-18
- [source] Dylan Patel claims Anthropic finished Mythos 2 but skipped release, building Mythos 3 — KeanuRave100 · 2026-08-19