Claude Code beats JetBrains' own agent on Kotlin coding benchmark

JetBrains released an open benchmark of 105 real Kotlin repository tasks, and Claude Code solved 90 of them. Running Opus 4.7 at xhigh effort, it scored 85.71%, beating JetBrains' own Junie agent and Codex on GPT-5.5, both at 81.9%. For teams choosing a coding agent for JVM work, that gap is measured instead of assumed.

Each task requires reading an issue, finding the relevant code, and shipping a patch verified in a container test suite, per JetBrains. Junie ran at max effort, JetBrains' highest setting, and still trailed.

Most agent benchmarks run on Python, so Kotlin developers have had to guess whether the scores translate. This one doesn't blur the variables. It names the agent, the model, and the effort level as separate settings.

What's next

JetBrains doesn't say whether Claude Code's 85.71% holds if the task set grows past 105. Junie and Codex could close a four-point gap on the next run. That's the number to watch as more agents get tested against it.