Two Official Pages Disagree on When Claude Haiku 4.5 Retires

Microsoft's retirement schedule says claude-haiku-4-5 retires on Microsoft Foundry this Sunday, November 15, 2026. Anthropic's deprecations page, which says its dates apply to Foundry, still lists the model as Active. Both pages were read this morning, November 13. Here is what each one says, why they can both be "right", and what I would do if I called Haiku 4.5 through Foundry. What each page says Model Anthropic's page Microsoft's Foundry schedule Claude Haiku 4.5 claude-haiku-4-5-20251001: Active, retirement "Not sooner than October 15, 2026" claude-haiku-4-5, versions 1 and 2: GA, retirement 2026-11-15 Claude Opus 4.5 claude-opus-4-5-20251101: Active, "Not sooner than November 24, 2026" claude-opus-4-5, version 1: GA, retirement 2026-11-24 Claude Sonnet 4.5 claude-sonnet-4-5-20250929: Deprecated, retires November 30, 2026 claude-sonnet-4-5, version 1: retirement 2026-11-30 Sources: Anthropic model deprecations and Microsoft Foundry model retirement schedule, both read November 13, 2026. Sonnet 4.5 agrees on both pages. Opus 4.5 agrees too, if you read Anthropic's "not sooner than" as a floor that Microsoft has turned into a date. Haiku 4.5 is the odd one. Anthropic's page is explicit about scope: its dates "apply to Anthropic-operated platforms", and Microsoft Foundry is on that list. Anthropic's Foundry guide adds that "Microsoft Foundry follows the Claude API lifecycle schedule." Read together, that says Haiku 4.5 on Foundry is Active. Microsoft's table says it has two days left. "Not sooner than" is a floor, not a date Anthropic's column is called "Tentative retirement date". For active models it holds a floor: the earliest day the model could retire. Haiku 4.5's floor passed four weeks ago and the model is still Active on the Claude API. A floor tells you nothing about when the end actually comes, only that it will not come before. Google does the same thing in other words. Its Gemini deprecations page says its shutdown dates "indicate the earliest possible dates on which a model might be retired." Microsoft sets the date by formula Microsoft's lifecycle policy says generally available models from Anthropic, DeepSeek, Fireworks and Mistral AI "follow a 12-month lifecycle instead of the standard 18-month lifecycle." The retirement date is set at launch, not announced later. That fits Opus 4.5: Anthropic's floor and Microsoft's date are the same day, November 24, 2026. It does not explain Haiku 4.5, which Anthropic still treats as an open-ended Active model. What retirement means on Foundry is stated plainly in the same policy: "All inference requests return 410 Gone." And: "Retirement dates aren't extendable." Which one do I believe? The one that runs the endpoint you call. If your requests go to https://{resource}.services.ai.azure.com/anthropic/, Microsoft's schedule is the date to plan for, until Microsoft changes its own table. Anthropic's page tells you about the Claude API. I do not know which page will turn out to be right on Monday morning, and neither page acknowledges the other. When two official sources disagree, the cheap move is to plan for the earlier date. Roughly 3,100 files on GitHub contain both claude-haiku-4-5 and services.ai.azure.com (GitHub code search, November 13, 2026). That is a crude proxy for "calls Haiku 4.5 through Foundry", but it says this is not a rounding error. What to check before Sunday Find the deployment. On Foundry the model field is your deployment name, which defaults to the model ID but can be anything. Search for the deployment name, not only for claude-haiku-4-5. Ask Azure, not the docs. Microsoft's Models API returns lifecycleStatus and deprecation.inference per model and region: GET https://management.azure.com/subscriptions/{sub}/providers/Microsoft.CognitiveServices/locations/{location}/models?api-version=2024-10-01 Watch the naming: in that API, Deprecated means retired, and Deprecating means what the docs call Deprecated. Pick the next model. Microsoft lists no replacement for Haiku 4.5. Anthropic's Foundry guide lists claude-haiku-5-5 on both hosting options. Test it with your own prompts before you switch. Handle 410. If a retired deployment returns 410 Gone, make sure your client does not retry it forever. Have you hit a case where two official sources gave you different end dates for the same thing, and which one turned out to be right? I'm Nabil. I build Since, which tracks what your code depends on and tells you before it breaks.