JetBrains Ships an Open Kotlin Benchmark: Claude Code (Opus 4.7 xhigh) Leads at 85.7% on 105 Repo Tasks

JetBrains Blog·high signal

JetBrains released its official Kotlin Benchmark of 105 real repository-level engineering tasks (interpret an issue, navigate the repo, produce a container-verified patch). Claude Code with Opus 4.7 xhigh solved 90/105 (85.71%), ahead of JetBrains Junie (Opus 4.7 max) and Codex (GPT-5.5 xhigh) tied at 81.9%. It's one of the few agent benchmarks that isolates a non-Python language and pins the exact agent+model+effort combo, which matters because most leaderboards blur those together.