Anthropic Retiring 1M Context Beta for Sonnet 4.5 and Sonnet 4 on April 30 — Migrate to 4.6 Models

Anthropic·medium signal

Anthropic announced the retirement of the 1M token context window beta for Claude Sonnet 4.5 and Claude Sonnet 4, effective April 30, 2026. After that date, the context-1m-2025-08-07 beta header will have no effect, and requests exceeding the standard 200k-token window will error. Developers should migrate to Claude Sonnet 4.6 or Opus 4.6, which support 1M context at standard pricing with no beta header required.