Claude Opus 5

Recent signals

• Anthropic says Opus 5.5 matches Fable 5.1 "on most tasks" while costing about 40% less to run than Opus 5; Opus 5.5 costs $4/1M input and $20/1M output tokens (Matthias Bastian/The Decoder) Sep 22, 2026
• Introducing Claude Opus 5.5 Sep 21, 2026
• Claude Opus 5 Helped Researchers Take Over OpenAI Staff Accounts via Chained Flaws Sep 19, 2026
• Security researchers in an OpenAI bug bounty program hacked OpenAI, accessing its "monorepo" on GitHub, using a cybersecurity version of Opus 4.8 and Opus 5 (Robert McMillan/Wall Street Journal) Sep 18, 2026
• Gen-1 Slides: Opus 5-level decks at a fraction of the cost Sep 9, 2026
• Artificial Analysis Coding Agent Index: GPT-6 Astra scored 67, roughly equal to Claude Opus 5, Fable 5, and Muse Spark 1.3, but trailing leader Fable 5.1's 70 (Artificial Analysis) Sep 4, 2026
• GPT-6 Astra scores 62.7% on ARC-AGI-3 with the standard harness and 99.9% with a new provider adapter harness; Claude Opus 5 scored 30.2%, and GPT-5.6 Sol 7.8% (Greg Kamradt/ARC Prize) Sep 3, 2026
• Muse Spark 1.3 with max reasoning, in limited preview for partners, scores 62 on the Artificial Analysis Intelligence Index, behind only Fable 5.1 and Opus 5 (@artificialanlys) Sep 2, 2026
• Claude Fable 5.1 made me a really nice animated pelican Sep 1, 2026
• Ramp data: Fable 5, launched in June, has plateaued at ~11% of spending on Anthropic tools, as companies shift to cheaper models; Opus 5 surpassed Fable 5 Aug 24, 2026
• Z.ai's GLM-5.3 scores 60 on the Artificial Analysis Intelligence Index, seven points above GLM-5.2, on par with Kimi K3, but below Opus 5's 63 and Fable 5's 62 Aug 19, 2026