Hierarchical skill evolution improves coding agent performance across environments
Hierarchical Skill Evolution for Coding Agent
Computation and Language
Summary
Coding agents often struggle to learn general routines because code is tied to specific tasks or projects. The authors created a method that learns coding skills step-by-step, first from single tasks, then from projects, and finally across multiple projects. This process keeps the core skills while removing task-specific details, allowing the agent to reuse and improve on what it learned in new coding situations. Their tests show these evolved skills help multiple coding models perform better on different benchmarks.
What this means in practice
- •For software development teams: Use evolved procedural coding skills to improve automated code generation across different projects and repositories.
- •For machine learning engineers: Enhance coding AI agents by integrating hierarchical skill distillation methods to boost code quality and adaptability across multiple environments.
Authors
Jun Gao, Yun Peng, Changhai Zhou, Yuhan Zhu, Xiangyu Zeng, Shiyang Zhang Yuhua Zhou, Luozheng Qin, Qian Qiao, Xiaoteng Ma, Baian Chen Weiyi Shang, Zhen Ming Jack Jiang, Lizhi Liao, Xiaoxue Ren
Abstract
Skills provide agents with reusable experience to guide future decisions without modifying the underlying model. However, coding trajectories are often entangled with task- and repository-specific contexts, making it challenging to distill procedural skills that generalize across diverse coding environments. To address this challenge, we present Hierarchical Skill Evolution (HSE), which progressively distills procedural knowledge from coding trajectories through hierarchical evidence aggregation. HSE first extracts task-level evidence from individual trajectories, then aggregates recurring evidence within the same repository to form repository-specific skill candidates, and finally consolidates consistent patterns across repositories into transferable skills across repositories. The evolution is driven by an external writer-evaluator loop that generates and assesses skills while keeping the underlying coding model frozen. The loop externally updates the writer and evaluator policies to improve subsequent skill generation and assessment. This hierarchy progressively filters task-specific details while preserving procedures that generalize across diverse coding environments. Successful trajectories yield reusable guidance for future tasks, while failed trajectories reveal recurring failure modes that guide avoidance and recovery. We evaluate HSE on SWE-bench Verified and DeepSWE, using GLM-5.2 across Pi and Claude Code harnesses and GPT-5.5 and Opus 4.8 with Pi. Across both benchmarks, 10 skills evolved solely from SWE-Gym improve coding performance across all evaluated settings, demonstrating transfer across benchmarks, coding models, and agent harnesses. We further evolve the skill library from target-benchmark trajectories without verifier feedback, relying solely on the learned evaluator for candidate assessment and achieving additional gains through benchmark-tailored skills.