Anthropic debuts Opus 5 at half the price of its Fable sibling

Anthropic released its Opus 5 AI model on Friday, claiming that it "comes close to the frontier intelligence of Claude Fable 5 at half the price." That's welcome news for enterprises beset by rising token costs. Fable 5 prices tokens at $10 / MTok input and $50 / MTok output, while Opus 5 prices tokens at $5 / MTok and $25 / MTok.

OpenAI's GPT-5.6 Sol sells for $5 / MTok input and $30 / MTok output. However, the tokens required to complete a task can vary from model to model, so it's also useful to assess how much each model costs to complete the same task.

Per Artificial Analysis, the weighted average cost (USD) per Intelligence Index task is $2.75 for Fable, $2.03 for Opus 5 (max), $1.

04 for GPT-5.6 Sol (max), and $0.95 for Kimi K3.

Opus 5 leads the Artificial Analysis Intelligence Index at 61, one point ahead of Fable. "Claude Opus 5 provides greatly improved performance for the same cost as its predecessor, Opus 4.8," Anthropic claims.

Opus 5 should offer customers more context to fill because Anthropic has put the model's system prompt on a diet. According to Claude Code engineer Thariq Shihipar, Anthropic removed 80 percent of the Claude Code system prompt for its latest models. As a result, the company's guidance for crafting prompts, skills, and CLAUDE.

md files has changed. "Across your system prompt, skills, and CLAUDE.md files, you may need to simplify just like we did," said Shihipar, adding that a command called claude doctor can help automatically optimize some prompts and skills.

Users of Opus 5 however may find the model's responses wordier – at their expense. Anthropic cautions, "Claude Opus 5's default user-facing responses run longer than prior Opus models'." Customers who don't want the new verbosity are advised, "To control response length, prompt for it explicitly."

Opus 5 scores close to Mythos on finding vulnerabilities in open source code (80 percent OSS-Fuzz benchmark score compared to 79.4 percent), but is significantly weaker in weaponizin