How Much Code Do Developers Really Let Agents Write?

Summary

JetBrains surveyed over 15,000 professional developers globally in 2026 to measure how much production code is generated by AI agents versus manual authoring. On average, respondents report that agents fully write approximately 47% of their code, while 38% involves AI assistance and 27% is written manually. Adoption varies across ecosystems, with Go, JavaScript, and TypeScript developers reporting the highest agentic code generation at 54% to 55%, while C and C++ developers retain the highest manual share. Senior developers lead adoption over juniors, with about a quarter delegating more than 80% of code generation to agents. Cluster analysis categorizes the developer population into agentic coders (31%), AI-assisted coders (47%), and manual coders (23%).

Takeaways

1. 1

   Developers using Go, JavaScript, and TypeScript report the highest shares of agent-generated code (54% to 55%), whereas C and C++ developers maintain the highest proportion of manually written code at 38% on average.

2. 2

   Among tool ecosystems, 42% of Codex users generate over 80% of their code with agents and 37% write zero code without AI, compared to 32% and 28% generating over 80% agentic code among Claude Code and Cursor users, respectively.

3. 3

   East Asian developers in China, Japan, and South Korea lead agentic code generation, with 32% to 35% producing over 80% of code via agents, roughly double the 16% observed across Europe and the United Kingdom.