Sonnet 5.5 tops the Coding Agent Index at max effort, while xhigh offers an attractive cost-performance trade-off: 63 points versus 68 for less than a quarter of the cost
In Claude Code, @AnthropicAI’s Sonnet 5.5 scores 68 at max versus 63 at xhigh. At $14.19 versus $3.33 per task, choosing xhigh cuts cost by 77% for 5.5 fewer Index points.
Max generates 4.8× as many output tokens and takes 3.4× as many turns. It improves all three benchmark scores, with the largest gain on Terminal-Bench 4.0: 58.1% → 66.2%.
Max effort scores 68 on the Coding AI agentAn AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.Full definition → Index versus 63 at xhigh, but costs $14.19 versus $3.33 per task. Engineers can choose effort levels with the cost-performance tradeoff quantified.
Terms in this piece · Glossary
token — The chunk of text a model reads and writes in — roughly three-quarters of a word — and the unit AI usage is billed in.
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
