Claude Opus 5.5 Tops Intelligence Index

Opus 5.5’s headline achievement is frontier-level performance with expensive, high-effort reasoning; developers should evaluate cost per completed task, not leaderboard position alone.

• –The composite score spans 10 evaluations, including coding, knowledge work, automation, science, and reasoning.
• –Max effort materially changes results: Opus 5.5 scores 57.6 versus 56.0 at xhigh and 53.6 at high.
• –Its cost per Intelligence Index task is lower than Fable 5.1’s $7.63, but remains costly for high-volume workloads.
• –A 1M-token context window plus text-and-image input suits large codebases, technical documentation, and multimodal analysis.
• –The “with fallback” configuration means real-world performance may reflect routing behavior as well as Opus 5.5 itself.