Claude 1M-token context window beta retired for Sonnet 4.5 and Sonnet 4; migrate to Sonnet 4.6 or Opus 4.6

AI Impact Summary

Claude has retired the 1M-token context window beta for Sonnet 4.5 and Sonnet 4. Requests exceeding 200k tokens will now error, affecting workloads that rely on long-context prompts or documents. To restore 1M-context capability, migrate to Claude Sonnet 4.6 or Claude Opus 4.6, where the extended window is generally available with standard pricing. Plan updating client libraries, revalidating model selections, and communicating the new limits to teams handling long-context NLP pipelines.