Claude Opus 5.5 Review: The 40% Cost Claim, the Real Math, and Who Should Migrate
Claude Opus 5.5 launched September 22, 2026 at $4/$20 per million tokens, a 20% cut from Opus 5 and the first Opus-tier model Anthropic has priced below its predecessor. Here is what the 40% savings claim actually means, the four breaking API changes, and the buy call for API teams and subscribers, with pricing dated 2026-09-22.
- ✓Per-token prices dropped 20% to $4/$20 input/output, the first Opus-tier model Anthropic has launched below its predecessor's price (per digitalapplied, September 22, 2026)
- ✓Cache reads fell 60% to $0.20 per million, and cache reads are the bulk of agentic and coding spend (per cellcog)
- ✕The headline 40% bundles the 20% price cut with a medium-instead-of-high default; pin high effort and you keep roughly the 20% (per digitalapplied)
- ✕Four breaking API changes reject Opus 5 code with a 400, and one of them needs a session-architecture change, not a parameter swap (per digitalapplied)
Claude Opus 5.5 is a stronger model at a lower sticker, and the price cut is the part you can bank. Anthropic ships it at $4/$20 per million tokens, down 20% from Opus 5, with cache reads down 60% to $0.20, per digitalapplied. If you run Opus 5 in production, migrate: change the model ID in a branch, clear the four breaking API changes, then compare two or three effort levels on real traffic before you move it. Benchmark legal, medical-coding, and tax agents first, because Vals AI measured regressions there. If you run Fable 5.1, Opus 5.5 lists at 40% of its per-token price and the first three breaking changes are already handled, so test it at high effort against your Fable baseline on your hardest tasks. If you hold a Pro, Max, or Team subscription, do nothing: five-hour limits rose 20% automatically, and the smart move is saving your one-off rate-limit reset for a long agent run instead of spending it on day one. The rating is 4.5 of 5. The half-point it gives up is migration friction plus the regression categories, not the model.