Anthropic's frequent Opus cadence, including the July 24 release of Opus 5 and September 1 launch of Fable 5.1, combined with unconfirmed rumors of an Opus 5.2 variant this week or by month-end, drives the tight clustering of Polymarket probabilities around September 22–29. Traders weigh the lab's history of 3–6 week intervals between major updates against the absence of official announcements or system cards, while competitive pressure from OpenAI and Google model timelines adds uncertainty. Recent platform integrations and safety-focused updates have not yet signaled a new flagship Opus, leaving resolution dependent on any imminent benchmark leaks or API identifiers that could shift the current 82% implied chance of a release near September 24.