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Latest / Frontier models and safety

Model releaseFrontierUSConfirmed

Anthropic releases Claude Opus 5.5 at 40% lower cost than Opus 5

See how this story connects

Source: Anthropic: Introducing Claude Opus 5.5

Anthropic released Claude Opus 5.5, the first model in its Claude 5.5 family, which it says performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5 on typical workloads. Input and output tokens cost $4 and $20 per million and cache reads $0.20. Anthropic said external evaluators including METR tested it before release, and that it ships with safeguards similar to Fable 5.1’s because it is comparable to Claude Mythos 5.1 in biology and cybersecurity.

Why it matters

Developers get Fable-level performance at Opus prices, with biology and cyber work gated through Anthropic’s verification programmes.

When
22 Sep 2026
ID
WTA-N-2026-0128
Who
Anthropic, METR

Summary by wheresthe.ai, from Anthropic. Checked against the source on 9 Oct 2026.

Read the original at Anthropic

Source copy: download the page as saved on 18 Oct 2026 (PDF). Also held by the Internet Archive.

Next stop on this Storyline: What happened nextAnthropic releases Claude Sonnet 5.5 with cyber safeguards from its top models

Cite this story

WTA-N-2026-0128: “Anthropic releases Claude Opus 5.5 at 40% lower cost than Opus 5.” wheresthe.ai, 22 Sep 2026. https://wheresthe.ai/d/anthropic-claude-opus-5-5-release-2026-09/ (source: Anthropic: Introducing Claude Opus 5.5).

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