Claude 1M-token context beta retired — migrate to Sonnet 4.6 or Opus 4.6

AI Impact Summary

Anthropic is retiring the 1M-token context window beta for Claude Sonnet 4. As a result, requests that exceed 200k tokens will return errors. To preserve long-context capabilities, migrate to Claude Sonnet 4.6 or Claude Opus 4.6, which provide the 1M-token window. Teams relying on long-context prompts or large document ingestion must update client endpoints, adjust tokenization and chunking strategies, and revalidate end-to-end prompts under the new window limits.