GPT-6 Astra posts first perfect score on Korean CSAT-style AI test, beating GPT-5.6 by 1.5 points

GPT-6 Astra scored a perfect 450 on a Korean College Scholastic Ability Test-style evaluation for large language models, becoming the first model to finish the full exam without losing a point. According to The Korea Daily, Astra earned full marks across Korean language, math, English, Korean history, and selected subjects including Physics I, Chemistry I, Biology I, and Social Studies and Culture. The runner-up, GPT-5.6, scored 448.5, leaving a gap of just 1.5 points. The score gap was narrow, but the compute gap was more pronounced. Astra used 357,000 tokens to complete the exam, versus 429,000 for GPT-5.6 and 562,000 for Claude Fable 5.1. That put Astra about 17% below the second-place model in token usage and 36% below Claude Fable 5.1. The test was run on GitHub using the actual 2026 academic year CSAT questions administered in 2025, with external web search barred during the evaluation. The report also cited professor Lee Seung-hyun, who said Astra’s edge appeared to come from structural efficiency in how it compressed and revised its solution plan while preserving its reasoning flow.