Next Mythos-Class Model released by September 9, 2026?
Realized · held to resolution+56%$100 paper stake
Polymarket64¢ → 100¢
Our position · YES64¢ → 100¢
Signal endedSep 1
Forecast updatedSep 1
Aug 29 forecast
Silent Fable 5.1 routing points to an advanced rollout, so the next Mythos-class model is likely by the deadline.
Recent reports of silent Fable 5.1 routing, candidate selection, and an early-access identifier suggest release preparations are advanced. Anthropic had also said more capable models were coming within months. However, no official launch materials have been verified, and some Mythos access remains restricted. A qualifying Fable 5.1 rollout is likely, with meaningful uncertainty from delays, rollback, or access that remains too limited.
Points to YES
- Reported routing to newer Fable checkpoints suggests production testing is underway, shortening the path to a general release and raising the chance of a timely qualifying launch.On August 28, a report said some Claude Code and web-app users were silently routed to reported newer checkpoints, including Fable 5.1.
- A reported early-access identifier for the selected candidate indicates that release infrastructure may already be prepared, making a near-term rollout more plausible.On August 28, a report said the identifier claude-melon-lp-eap had appeared and assessed Melon as Fable 5.1.
- Anthropic's stated expectation of more capable models within months supports a late-summer successor and makes the reported rollout consistent with its announced development timeline.On June 9, Anthropic said more capable models were expected in the coming months.
Points to NO
- The absence of verified official launch materials leaves the reported model short of public confirmation and increases the risk that testing does not become a qualifying release in time.As of an August 27 research cutoff, no official launch post, API model identifier, pricing page, system card, rate-limit notice, or downloadable weights for Opus 5.1 had been verified.
- Anthropic's continued use of restricted Mythos programs shows that safety and access controls could delay broad availability or leave a new model accessible only through nonqualifying channels.On August 27, Anthropic said it was working with the US government on a restricted-access program for life-sciences professionals to use Mythos-class models.
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