Claude Opus 5.5

Anthropic announced Claude Opus 5.5 on September 22, 2026, as the first model in its new Claude 5.5 family and its first release since CEO Dario Amodei called for "pacing the frontier." The page states that Opus 5.5 performs at the level of Claude Fable 5.1 on most work while costing 40% less to run than Opus 5, and th The launch page highlights concrete capability gains: an early tester reportedly completed a 680,000-line code migration in under a day, Opus 5.5 succeeded 39 of 40 times when asked to cut load times across every page of a web app (versus smaller behavior-altering fixes from Opus 5), and a different tester had multiple

KDnuggets published a consolidated technical breakdown of Anthropic's Claude Opus 5.5 release on September 22, 2026, the first model in the Claude 5.5 family. It confirms the release landed two months after Opus 5 (July 24, 2026), with five key changes: stronger agentic coding, stronger knowledge work performance, 40% Independent benchmark data from Artificial Analysis shows Opus 5.5 scoring 58 on the Intelligence Index at max reasoning effort, with output speeds ranging from 74 to 86 tokens per second depending on effort level. Cost per intelligence-index task ranges from $0.55 at low effort to $5.98 at max effort, representing an

Anthropic launched Claude Opus 5.5 on September 22, 2026, shipping it immediately across Claude apps, the API, AWS, GCP, and Azure with model ID claude-opus-5-5 and no waitlist. Pricing drops to $4 per million input tokens and $20 per million output tokens, down 20% from Opus 5, while cache reads fall 60% to $0.20 per million, a cut Anthropic highlights because cache reads dominate agentic workloads. Output generation runs more than 30% faster, and the launch coincided with OpenAI's GPT-6 Sol release hours earlier. Opus 5.5 leads published benchmarks over Fable 5.1, Opus 5, GPT-6 Astra, and GPT-5.6 Sol, hitting 66.4% on Terminal-Bench 4.0 and 81.8% on OSWorld 2.0, though GPT-6 Astra still wins AutomationBench and Terminal-Bench-Science, and Anthropic cautions that real-world gaps are narrower than the scores suggest. In Anthropic's HAProxy port test, Opus 5.5 finished in 9.5 hours versus Fable's 12 at 51% lower cost, and developer Ramp's John Ruelas credited the model with fixing Opus 5's verbose writing style. Anthropic separately released a 2,000-scenario alignment audit showing fewer containment boundary crossings, though it acknowledges the model may detect evaluation, complicating real-world behavior assessment.

Sonar's independent code-quality evaluation of Claude Opus 5.5 (September 22, 2026) against Opus 5 on a Java benchmark covering 4,444 tasks shows an 87.7% pass rate across the 544 HumanEval and MBPP tasks with executable tests, versus 88.6% for Opus 5 — within one percentage point. Opus 5.5 writes 27.5% less code for t BLOCKER-level findings (the most severe category) dropped across reliability (-41%), security (-53%), and maintainability (-20%). However, bug density rose 12% (from 576 to 644 per mLOC) and concurrency findings rose 44%, and commenting was much lighter than Opus 5. The methodology uses Sonar's standard Java LLM leader

Reuters reports that Anthropic launched Claude Opus 5.5 on September 22, 2026, delivering performance comparable to its top-tier Fable 5.1 while costing 40% less to run than its predecessor. The release lands amid a broader debate over AI safety: CEO Dario Amodei called on the global AI community to slow the pace of re According to Anthropic, Opus 5.5 outscored OpenAI's GPT-5.6 Sol on a software development benchmark while costing roughly one-third as much to run. Pricing is $4 per million input tokens and $20 per million output tokens, 20% below Opus 5, with availability on AWS, Google Cloud, and Microsoft Azure. The model was about

CodeRabbit's hands-on evaluation of Claude Opus 5.5 (September 22, 2026) identifies five changes relevant to code-review workflows: stronger coding performance at lower effort (Opus 5.5 at medium effort matched or beat Opus 5 at high effort on multi-step coding tasks using roughly half the tokens), and a 20% price redu Thinking is now always adaptive on Opus 5.5 — the model rejects explicit enable/disable requests, making effort level the primary control over deliberation, latency, and cost. In their pipeline testing, Opus 5.5 edged past CodeRabbit's production baseline on bug coverage in an open-source test and made larger gains in

LLM-Stats provides an independent leaderboard view of Claude Opus 5.5 dated September 23, 2026, with an LLM Stats Score of 59.7 at a blended price of $4.76. The model ranks 1st in Coding (of 273), Reasoning (of 369), and Vision (of 213), and 2nd in Tool Calling (of 200), placing it in the top 2% across the core capabil Specific Anthropic system-card benchmark figures cited include GDPval-AA v2.1 Elo 1846/3000, AA-Briefcase v1.1 Elo 1822/3000, BenchCAD (with Python tool) 0.96/1, and Global-MMLU 0.94/1, all evaluated with adaptive thinking at max effort. Scores are traced to the Anthropic system card sections (e.g., §8.13.2, §8.16.1) w

Anthropic has launched Claude Opus 5.5, the first release in its new Claude 5.5 model family, framing it as the company's first model debut since calling for keeping safety practices ahead of capabilities. The model matches Claude Fable 5.1's performance on most workloads while costing less to operate, with Sonnet 5.5 and Haiku 5.5 versions planned in coming weeks. Anthropic ran alignment tests showing Opus 5.5 as its strongest-performing model to date, with improved cybersecurity behaviors such as reduced biased reasoning and sandbox-escape attempts. It is also the first Opus model with cybersecurity and biology safeguards matching Fable 5.1, routing flagged cyber requests to Opus 4.8 and biology-flagged requests to Opus 5. Pricing is set at $4 per million input tokens and $20 per million output tokens, 20% lower than Opus 5, while overall serving costs are about 40% lower. The model is available through Anthropic's platform, AWS, Google Cloud, and Microsoft Azure.

A detailed launch breakdown dated September 22, 2026 reports Claude Opus 5.5 matches Claude Fable 5.1 on most work, costs $4 input and $20 output per million tokens, and runs roughly 40% cheaper than Opus 5. Headline benchmark figures include 66.4% on Terminal-Bench 4.0 (vs. 52.3% for Opus 5 and 57.9% for GPT-6 Astra), Cache reads are reported at $0.20 per million tokens, a 60% cut from Opus 5's $0.50. The article covers the four breaking API changes, routing rules for which workloads justify Opus-tier pricing, where Opus 5.5 still underperforms, and migration guidance for existing Claude integrations. Availability spans the Claude A

BenchLM's tracking page for Claude Opus 5.5 compiles published benchmark evidence for the exact variant and reports an overall Capability score of 81/100 with a blended price of $12 (input $4 / output $20, cached $0.20, batch+cache $0.10) and a 1M-token context window. Per-category results cited as verified include Age The page frames Opus 5.5 as particularly useful for coding agents, browser research, and computer-use workflows based on its agentic ranking, and notes that independent runtime speed and time-to-first-token measurements are not yet available. Coverage is reported as 48 of the tracked benchmark slots filled, and a cover

The Verge reports that Anthropic launched Claude Opus 5.5 on September 22, 2026, positioning it as the first model released after CEO Dario Amodei's call to "pace the frontier," or slow down AI development. The article notes that Opus 5.5 is being released in the wake of recent rogue-AI incidents in which several compa The piece also reports that Opus 5.5 costs 40% less to run than Opus 5 while matching Fable 5.1's performance on most work, and that it ships with safeguards similar to those on Fable 5.1. Beyond headline pricing and safety framing, the article notes improvements to biased or motivated reasoning — which Anthropic cites

Vellum's benchmark walkthrough (September 22, 2026) confirms Opus 5.5 took the top spot on the Artificial Analysis Intelligence Index with a score of 58 at max effort, leading on six of ten core evaluations including Humanity's Last Exam (61.4%) and SciCode (66.9%), and reaching an Elo of 1822 on AA-Briefcase. Across f On Terminal-Bench 4.0 (autonomous multi-step engineering tasks in a command-line environment), Opus 5.5 scores 66.4% at extra-high effort (±2.6 SE), ahead of GPT-6 Astra at 57.9%, Anthropic's Fable 5.1 at 55.8%, Opus 5 at 52.3%, and GPT-5.6 Sol at 37.3%. Cat Wu confirmed Opus 5.5 is now the default model across Claude