Claude Fable 5 vs Opus 4.8: Which Wins?

Key insights

• Claude Fable 5: Anthropic released this model as its most capable broadly available Mythos-class model on June 9, 2026, aimed at hard reasoning and long‑horizon tasks in professional settings.
  
• Safety fallbacks: Fable 5 automatically applies stronger safeguards on high‑risk topics, blocking some replies or switching behavior to reduce misuse risk while keeping power for safe tasks.
  
• Claude Opus 4.8: Opus 4.8 remains cheaper and is still used when Fable 5’s safety filters route sensitive prompts to a fallback, so Fable’s output can vary by topic.
  
• Capabilities and benchmarks: Tests and reports show notable gains in coding, autonomous software work, UI and game tasks, and analytics benchmarks, though safety routing can lower scores on cyber/bio evaluations.
  
• Hands-on tests: The review ran four practical checks—reading a chart in a PDF, finding a hidden spreadsheet error, building a report from multiple files, and probing restricted topics—to show where Fable 5 helps and where it defers to Opus 4.8.
  
• Pricing and takeaway: Fable 5’s API pricing is higher (about $10 per million input tokens and $50 per million output tokens) and includes a limited free window on paid plans; choose Fable 5 for the hardest reasoning and long‑context work but keep Opus 4.8 for cost and routed cases.
  

Keywords

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