# Claude Opus 5.5 Claude Opus 5.5 is an AI model released by Anthropic on Sep 22 2026. It has a 1M context window. Tracked results include 67.7% on Humanity's Last Exam (with tools), 54.4% on FrontierCode v1.1 (Main) (main split) and 66.4% on Terminal-Bench 4.0. ## Facts | Field | Value | | --- | --- | | Model | Claude Opus 5.5 | | Developer | Anthropic | | Release date | Tuesday, Sep 22 2026 | | Licensing | Proprietary | | Context window | 1M | ## API pricing All rates in USD per 1,000,000 tokens, pay-as-you-go. | Tier | Input | Cached input | 5 min cache write | 1 hr cache write | Output | | --- | --- | --- | --- | --- | --- | | All documented contexts | $4.00 | $0.20 | $5.00 | $8.00 | $20.00 | Cache reads are priced at 0.05x the base input price on this model, against 0.1x on Opus 5. Anthropic also publishes a Fast mode for this model at exactly twice the standard rate — $8.00 per million input tokens and $40.00 per million output — on the Claude API only, with up to 2.5x the output speed. Verified September 22, 2026 against the first-party source: https://platform.claude.com/docs/en/about-claude/pricing ## Tracked benchmark scores | Benchmark | Score | Source | What it measures | | --- | --- | --- | --- | | FrontierCode v1.1 (Main) (main split) | 54.4% | Lab | A set of very hard, frontier-difficulty coding tasks an AI agent has to complete end to end. The score is the share of tasks in the main split it solves. Higher is better. | | Terminal-Bench 4.0 | 66.4% | Lab | Can the AI work in a command-line terminal — running commands and finishing technical setup tasks the way a developer would? Version 4.0 recalibrated how much time, CPU and memory each task gets, removed eight tasks and fixed nineteen, so fewer runs fail for reasons that have nothing to do with the model. Scores are not comparable with earlier versions. Higher is better. | | Terminal-Bench-Science 0.1 | 58.7% | Lab | The same command-line setup as Terminal-Bench, pointed at scientific work: the AI has to drive research tooling and computational workflows through to a result, rather than administer a machine. Version 0.1 is the first release of the task set, and scores run lower than on the general board. Higher is better. | | Humanity's Last Exam (with tools) | 67.7% | Lab | Humanity's Last Exam — extremely hard expert questions across many subjects. “With tools” means the AI is allowed to search the web or run code while answering. Higher is better. | | OSWorld 2.0 | 81.8% | Lab | Can the AI actually operate a computer — clicking, typing, and using real apps — to finish tasks on its own? Version 2.0 is a harder, refreshed task set. Higher is better. | | AutomationBench | 40% | Lab | Tests whether the AI can run real multi-step business workflows — the kind of end-to-end office processes companies want to automate — from start to finish. Higher is better. | | GDPval-AA v2.1 | 1846 | Lab | economically valuable knowledge work (v2.1, Crowd-BT Elo fit) | | Chartography (with tools) | 89% | Lab | A chart-centred test run with tools available to the AI, reported separately from the chart-reading benchmarks above it. Higher is better. | ## About Claude Opus 5.5 Claude Opus 5.5, released September 22, 2026, succeeded Claude Opus 5 at Anthropic's Opus tier eight and a half weeks after it and three weeks after Claude Fable 5.1 took the top of the lineup. It arrived with a price cut: $4 per million input tokens and $20 per million output against Opus 5's $5 and $25, with cache reads at $0.20 per million, less than half Opus 5's $0.50, and cache writes at $5. Its launch table did something no earlier Opus release had done: it put the Opus model ahead of the Fable model above it on every board the two shared. At launch it scored 66.4% on Terminal-Bench 4.0 against Fable 5.1's 55.8% and Opus 5's 52.3% under Anthropic's own harness, 54.4% on the main split of FrontierCode v1.1, a GDPval-AA v2.1 Elo of 1846 for knowledge work where Fable 5.1 sat at 1735, and 67.7% on Humanity's Last Exam with tools. All of those were the best published scores at the time. The rest of the card was agentic breadth. Opus 5.5 reached 81.8% partial completion on OSWorld 2.0 computer use, 89.0% on Chartography with tools and 58.7% on Terminal-Bench-Science 0.1, double Opus 5's 29.0% and six points behind GPT-6 Astra's 64.6%. On AutomationBench, run by Zapier during early access, it scored 40.0%, a point and a half short of GPT-6 Astra's 41.4% and up from Opus 5's 26.9%. Anthropic ran the table with production safeguards enabled, so cybersecurity tasks the classifiers intercepted were completed by Claude Opus 4.8 and biology and frontier-LLM-development tasks by Claude Opus 5, which it said likely lowered the reported numbers. The Terminal-Bench 4.0 result was reported at xhigh effort with a standard error of ±2.6 points; every other Claude figure used adaptive thinking at max effort. ## Questions and answers ### When was Claude Opus 5.5 released? Claude Opus 5.5 was released by Anthropic on Tuesday, Sep 22 2026. ### Who made Claude Opus 5.5? Claude Opus 5.5 was built by Anthropic. AI safety company building the Claude family of models. Founded in 2021 by former OpenAI researchers. ### How much does Claude Opus 5.5 cost? Claude Opus 5.5 costs $4.00 per million input tokens and $20.00 per million output tokens through the Anthropic API. Cached input is $0.20 per million tokens. Rates are pay-as-you-go API prices verified against Anthropic's published pricing on September 22, 2026. ### What benchmark scores did Claude Opus 5.5 get? Claude Opus 5.5 reports 8 tracked benchmark scores — FrontierCode v1.1 (Main) (main split): 54.4%; Terminal-Bench 4.0: 66.4%; Terminal-Bench-Science 0.1: 58.7%; Humanity's Last Exam (with tools): 67.7%; OSWorld 2.0: 81.8%; AutomationBench: 40%; GDPval-AA v2.1: 1846; Chartography (with tools): 89%. Tracked scores may come from lab reports or independent benchmarks; source details accompany the benchmark data. It holds the best score among all models tracked here on FrontierCode v1.1 (Main) (main split), Terminal-Bench 4.0, Humanity's Last Exam (with tools), OSWorld 2.0, GDPval-AA v2.1 and Chartography (with tools). ### What is the context window of Claude Opus 5.5? Claude Opus 5.5 has a context window of 1M. That is the maximum amount of input plus output the model can hold in a single request. ### Is Claude Opus 5.5 open source? No. Claude Opus 5.5 is a proprietary model. The weights are not published — it is available only through the provider's own API, apps, or partner platforms. ### What came before and after Claude Opus 5.5? Anthropic's previous tracked release was Claude Mythos 5.1 on Sep 1 2026, 21 days earlier. It is the most recent Anthropic model tracked on AI Release Tracker. --- Canonical page: https://aireleasetracker.com/model/anthropic/claude-opus-5.5 Full dataset: https://aireleasetracker.com/llms-full.txt · JSON: https://aireleasetracker.com/models.json Source: AI Release Tracker (https://aireleasetracker.com). Most benchmark scores come from lab launch material; gathered results identify the leaderboard that published them.