Anthropic's Claude Opus 5 costs well below Fable 5 while matching or beating it across most benchmarks

2026-07-25 · Source: The Decoder · Field: Technology & Digital — Artificial Intelligence & Machine Learning, Data Science & Analytics · Depth: Intermediate, medium

Summary

Anthropic's Claude Opus 5, released July 25, 2026, is a leading AI model, scoring 61 on Artificial Analysis's Intelligence Index, ahead of Claude Fable 5 (60) and GPT-5.6 Sol (59). It excels in coding, tying for first on the Artificial Analysis Coding Index (67) and matching GPT-5.6 Sol on Terminal-Bench v2.1 (89%). While strong in scientific reasoning (53% on Humanity's Last Exam), its factual accuracy is a concern, with a 50% hallucination rate. Epoch AI confirms its competitive standing with an Epoch Capability Index of 159. Opus 5 generally offers lower costs, with an average Intelligence Index task at \$2.03 versus Fable 5's \$2.75. The "high" reasoning tier often provides optimal coding results (89.8% on Vibe Code Bench) and better value. In knowledge work (AA-Briefcase), Opus 5 "max" achieves an Elo of 1720, significantly surpassing Fable 5 (1574), with the "high" tier costing \$10.41 per task.

Key takeaway

For AI Scientists and Machine Learning Engineers evaluating frontier models, you should consider Claude Opus 5 for its strong performance in coding and knowledge work, especially at its cost-effective "high" reasoning tier. However, carefully assess its 50% hallucination rate for applications requiring high factual accuracy. Optimize costs by utilizing the "high" tier for coding and employing cache for token efficiency.

Key insights

Claude Opus 5 leads benchmarks in capability and cost-efficiency, but its high hallucination rate demands careful application.

Principles

• Frontier models are tightly competitive.
• Higher reasoning tiers don't always mean better results.
• Cost-performance trade-offs are critical.

In practice

• Prioritize "high" reasoning tier for coding tasks.
• Evaluate Opus 5's 50% hallucination rate for high-stakes use.
• Utilize cache for token cost savings.

Topics

• Claude Opus 5
• Large Language Models
• AI Benchmarking
• Cost Optimization
• Hallucination Rate
• Knowledge Work
• Coding Agents

Best for: CTO, AI Engineer, NLP Engineer, AI Scientist, Machine Learning Engineer, Director of AI/ML

Related on AIssential

• Anthropic's Claude Opus 5 delivers near-Fable 5 performance at half the token price — Claude Opus 5 offers competitive performance against Fable 5 and GPT-5.6 Sol at significantly reduced token costs.
• A Cheaper Claude, a Cracked Agent, and $52 Million for Your Iris — Frontier AI models are achieving higher performance at significantly reduced costs, making advanced capabilities more accessible.
• Claude Opus 4.8 is here. Is it as good as they say? — Opus 4.8 excels in one-shot coding but struggles with complex edge cases, existing codebases, and factual grounding.
• Anthropic's Opus 5 surprise — Claude Opus 5 delivers Fable 5-tier intelligence at half the cost, setting new benchmarks in agentic tasks and complex problem-solving.
• OPUS 5 CLICK NOW — Claude Opus 5 redefines LLM value, offering superior performance at a significantly lower cost per task.
• Claude Opus 5 Is THE GREATEST AI Model EVER?! Beats Fable & CHEAPER! (Fully Tested) — Claude Opus 5 offers frontier-class AI capabilities at significantly lower cost than competitors, excelling in complex reasoning and autonomous code generation.

See Counsel's argued verdicts on the open AI decisions leaders are weighing →

Open in AIssential →

Editorial summary, takeaway, and curation by AIssential. Original article published by The Decoder.