Anthropic shipped Opus 5.5 on September 22, 2026 — same 1M context as [Opus 5](/posts/claude-opus-5-marketers/) and [Fable 5.1](/posts/claude-fable-5-1-marketers/), but $4/$20 instead of $5/$25, cache reads cut 60% to $0.20, and a writing-style fix that actually lands. The number that matters for marketers isn't a benchmark — it's that 60% cache-read cut. Four jobs Opus 5.5 earns from Opus 5 this week, three where Fable 5.1 or Opus 5 still wins, one routing principle that holds, and the four breaking API changes you need to patch before Monday.
