Anthropic launches Claude Opus 5.5: 40% cheaper to run than Opus 5

Anthropic introduced Claude Opus 5.5 on September 22 — the first model in its new Claude 5.5 family. The company says it performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5.

Performance and cost

Anthropic reports that early testers saw large gains on complex work. One tester completed a 680,000-line code migration in less than a day — work the company says would have taken an engineering team weeks. Asked to cut load times on every page of a web app, Opus 5.5 succeeded in 39 of 40 cases, while Opus 5 made smaller improvements that also altered the app's behaviour.

Cache reads, which the company says make up most agentic and coding costs, are $0.20 per million tokens, 60% less than Opus 5, and output is generated more than 30% faster. A fast mode of up to 2.5x speed is available in Claude Code and the Claude Platform at $8 per million input tokens and $40 per million output tokens.

Benchmarks and customer results

On FrontierCode v1.1, which measures whether an agent's code changes would be merged, Opus 5.5 scores 54.6% at default effort — ahead of every other model and above GPT-6 Astra's top score of 53.3%, at roughly a fifth of the cost per task. On Terminal-Bench 4.0 it beats Opus 5 at maximum effort for about a fifth of the cost, and matches GPT-6 Astra at about 40% of the cost. On GDPval-AA v2.1, covering real work across 44 occupations, it reaches 1846 Elo.

Customers quoted by Anthropic report similar gains. Hebbia says Opus 5.5 covered 86.6% of an expert finance rubric against 60.3% for Opus 5, and Spotify reports matching Opus 5's quality on agentic coding tasks in about half the turns, time and output tokens.

Safety and safeguards

Anthropic says Opus 5.5 achieves the best scores to date on its automated behavioural audit, which tests Claude across nearly 2,000 scenarios, and is its strongest model on most measures of honesty. In a new containment evaluation it attempted to circumvent boundaries about 85% less often than Opus 5 or Claude Mythos 5.1. In a benchmark run by the security firm Gray Swan it ties Fable 5.1 for the lowest prompt-injection success rate of any model tested.

It is the first Opus model to launch with safeguards similar to Fable 5.1's for cybersecurity, biology and distillation; most cybersecurity tasks are re-routed to Opus 4.8. Opus 5.5 ships with "preserved thinking", an anti-distillation measure that applies to API accounts created on or after 31 August 2026, and is no longer offered with thinking mode switched off.

Availability

Claude Opus 5.5 is available now on Amazon Web Services, Google Cloud and Microsoft Azure; on the Claude Platform the model identifier is claude-opus-5-5.