Anthropic's "not sooner than" dates are a floor, not a shutdown — and Sonnet 4.5's floor is 46 days away

Anthropic's deprecation page carries a column headed "tentative retirement date", and every active model has an entry in it. Claude Sonnet 4.5: not sooner than 29 September 2026. Claude Haiku 4.5: not sooner than 15 October 2026. Claude Opus 4.5: not sooner than 24 November 2026. Read quickly, that looks like a shutdown schedule for most of the Claude line inside the next four months. It is the opposite. The phrase "not sooner than" is a floor: Anthropic is promising the model will not be switched off before that day. Nothing in it says the model will be switched off on that day, or in the month after it. Real retirements look different — they get an announcement, a named replacement and a fixed date, and Anthropic commits to at least 60 days' notice before pulling a publicly released model. Claude Opus 4.1 went that way: deprecated 5 June 2026, retired 5 August 2026, replacement named as Opus 4.8. The distinction matters because the floors are drifting into view. Sonnet 4.5's expires in 46 days, and it is the oldest Claude still on sale: released 29 September 2025, 200,000 tokens of context, manual extended thinking, and still accepting the temperature and top_p controls that Anthropic stopped honouring from Opus 4.7 onward. A team running on it has no announced deadline — but also no promise beyond the end of September. There is a second trap in the same table. The dates apply to Anthropic-operated platforms only: the Claude API, Claude Platform on AWS and Microsoft Foundry. Amazon Bedrock and Google Cloud set their own retirement schedules, so the same model can be alive on one and gone from another. Claude 3 Haiku is the worked example — retired by Anthropic on 20 April 2026, with a separate shutdown date on Google Cloud months later. The practical rule for anyone tracking model lifecycles: treat "not sooner than" as the earliest possible bad news, not the expected one, and check the deprecation history rather than the status table for anything that has actually been scheduled. We have added profiles of Claude Sonnet 4.5 and Claude Sonnet 4.6 to the catalogue today, and both carry their guarantee dates as guarantees, not as retirement dates.