Anthropic shipped Sonnet 5.5 on September 28, 2026 — same $2/$10 as Sonnet 5, same 1M context, 30%+ faster, up to 30% cheaper per task, and on GDPval-AA it sits two Elo points under Opus 5.5. Five jobs Sonnet 5.5 already replaced in its first day on real marketing work, three where Opus 5.5 or Sonnet 5 still wins, and the routing principle that matters now that the Sonnet tier can carry real marketing work.
