Overview
Anthropic introduced Claude Opus 5.5 on September 22, 2026. It is the first model in the new Claude 5.5 family, performing at the level of Claude Fable 5.1 on most work while costing 40% less to run than Opus 5. The model ID is claude-opus-5-5 and pricing is $4 / $20 per million tokens. Claude Sonnet 5.5 and Claude Haiku 5.5 will follow in the coming weeks.
Key features
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Fable 5.1-level performance at a lower cost
Opus 5.5 performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5. In one workload described in the announcement, it matched Opus 5’s quality in about half the turns, time, and output tokens, cutting the cost of that workload by 40 to 50%.
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Lower pricing, especially for cache reads
Input and output tokens are $4 and $20 per million, 20% less than Opus 5. Cache reads, which make up the majority of agentic and coding work costs, are $0.20 per million tokens, 60% less than Opus 5.
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Faster output and Fast mode
Opus 5.5 generates output more than 30% faster than Opus 5. Fast mode for Opus 5.5 is also available in Claude Code and the Claude Platform with up to 2.5x speed.
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Gains on agentic coding and knowledge work
Key results against Opus 5 are below. One tester completed a 680,000-line code migration in less than a day, work that would have taken an engineering team weeks. On another task, Opus 5.5 finished in 63 minutes compared to 93 for Opus 5, and cost 50% less to produce.
Benchmark Opus 5.5 Opus 5 Terminal-Bench 4.0 66.4% 52.3% CursorBench 4.0 57.8% 46.6% OSWorld 2.0 (partial) 81.8% 74.0% GDPval-AA v2.1 1846 Elo 1708 Elo -
Higher usage limits on subscription plans
Five-hour usage limits are increasing on Pro, Max, Team, and seat-based Enterprise plans. Subscription users also get a rate limit reset, which they can save and use whenever they choose.
Notes
- No longer available with thinking switched off — as with Fable 5.1, Opus 5.5 is not available with “thinking” mode switched off. Unless otherwise noted, the announced results use adaptive thinking at max effort.
- Cybersecurity tasks re-routed to Opus 4.8 — because Opus 5.5 has extremely strong cyber capabilities, it ships with cybersecurity safeguards similar to Fable 5.1’s, and most cybersecurity tasks will be re-routed to Opus 4.8.
- Biology safeguards and the Life Sciences Verification Program — Opus 5.5 uses the same biology safeguards as Fable 5.1. Research and development work impeded by these safeguards can apply to the new Life Sciences Verification Program.
- Preserved thinking — the anti-distillation safeguard introduced with Fable 5.1 stops API users from editing Claude’s prior context in an attempt to extract Claude’s reasoning.
- Watermarking — as with Fable 5.1, Opus 5.5 comes with watermarking measures to comply with the EU AI Act.
- Safety evaluation — on an automated behavioral audit across nearly 2,000 scenarios, Opus 5.5 scored better than any recent Claude model on nearly every measure of misaligned behavior. It was tested before release by external evaluators, including Frontier Design and METR.
- Default Opus model in Claude Code — starting with Claude Code 2.1.280, Opus 5.5 is the default Opus model, and the default model on Pro and Team Standard plans changed from Sonnet to Opus.