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Anthropic to retire Claude Sonnet 4.5 and Opus 4.8 fast mode Nov 30

By PulseAugur Editorial · [1 sources] ·

Anthropic is retiring the claude-sonnet-4-5-20250929 model from its Claude API on November 30, 2026. This retirement means that any requests made to this model after that date will result in an error, rather than a fallback or slowdown. Additionally, the fast mode for Claude Opus 4.8 will also be removed on the same date, leading to similar errors for requests using it. Developers are advised to update their integrations by finding all instances of the old model identifier, adjusting their requests to use the new model (claude-sonnet-5-5) and potentially re-tuning sampling parameters like temperature, top_p, and top_k, which may cause issues with API version 2026-10-21. AI

IMPACT Developers using older Claude models must update their integrations before November 30, 2026, to avoid service disruptions.

RANK_REASON This is a notice about the deprecation and retirement of specific model versions and features within an API, rather than a new release or significant industry event.

Read on dev.to — LLM tag →

AI-generated summary · Google Gemini · from 1 sources. How we write summaries →

Anthropic to retire Claude Sonnet 4.5 and Opus 4.8 fast mode Nov 30

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This is a notice about the deprecation and retirement of specific model versions and features within an API, rather than a new release or significant industry event.
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COVERAGE [1]

  1. dev.to — LLM tag TIER_1 English(EN) · iloblique ·

    Claude Sonnet 4.5 retires on November 30. The migration is not one line

    <p>On November 30, 2026, Anthropic retires <code>claude-sonnet-4-5-20250929</code> from the Claude API. After that date, requests to it fail. They do not slow down or fall back to something close. They return an error. As of November 9, that is 21 days away. The same day, fast mo…

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