Anthropic releases Claude Opus 5.5: first Claude 5.5 model; Fable 5.1-level on most work, ~40% cheaper than Opus 5

Why it matters

【Official release】

Anthropic released Claude Opus 5.5 on 2026-09-22 — the first model in the Claude 5.5 family. Canonical page: https://www.anthropic.com/claude-opus-5-5 (also listed on the Newsroom). CMS featuredGrid/siteSettings _updatedAt≈2026-09-22T16:27:50Z is a verifiable approximate go-live; the page eyebrow is day-level only (September 22, 2026). API id: `claude-opus-5-5`; Anthropic says it is available on the Claude Platform and on Amazon Web Services, Google Cloud, and Microsoft Azure.

【Verifiable points】

Official claims: performs at Claude Fable 5.1 level on most work; ~40% lower cost than Opus 5 on typical workloads. Pricing vs Opus 5: input $4 / output $20 per MTok (~20% lower each); cache reads $0.20 per MTok (~60% below Opus 5’s $0.50); cache writes $5. Strengths highlighted in agentic coding, computer use, and knowledge work. Pre-release external evaluation included Frontier Design and METR; Anthropic says Opus 5.5 is its strongest model to date on the automated behavioral audit. Because biology/cyber capabilities are comparable to Mythos/Fable-class models, it ships with safeguards similar to Fable 5.1 (cyber tasks often fall back to Opus 4.8; biology via Life Sciences Verification; plus distillation/preserved-thinking controls). Sonnet 5.5 and Haiku 5.5 are said to follow in the coming weeks.

【Our take】

No on-site Opus 5.5 event found; this is a new item, not a rehash. Frontier flagship model release with material AI-progress impact → surfaces include home_week. Facts limited to official visible text; benchmark tables and System Card details are not restated line-by-line here. Do not confuse with on-site e/665 (Qwen Code v0.24.4); do not touch e/663 or e/664.