Uncovering the Coding Personalities of Leading LLMs

The rapid integration of LLMs into the SDLC has marked a paradigm shift in how we create code. While performance benchmarks have been the standard for evaluating these powerful tools, they often present an incomplete picture, focusing on the models' ability to solve complex coding challenges rather than the quality, security, and maintainability of the code they produce. This session delves into the findings of Sonar's research in this area, which moves beyond traditional evaluations to reveal the distinct "coding personalities" of today's leading LLMs.

Sonar has created an analysis framework that leverages deep static code analysis (from SonarQube) to assess LLM-generated code across thousands of Java programming assignments. We'll explore the strengths that have driven LLM adoption, such as their proficiency in generating syntactically correct code and solving algorithmic problems. However, we will also uncover critical shared flaws that persist across all evaluated models, including a significant lack of security consciousness, a struggle with fundamental software engineering discipline, and an inherent bias towards producing messy, high-debt code.

Our research surfaced unique, quantifiable "coding personalities" for models like Anthropic's Claude Sonnet, OpenAI's GPT series, and Meta's Llama models. By analyzing metrics such as verbosity (lines of code), complexity (cognitive and cyclomatic), and communication style (comment density), we can define distinct archetypes for each LLM—from "The Senior Architect" that writes sophisticated but potentially fragile code, to "The Rapid Prototyper" that prioritizes speed at the cost of technical debt.

Furthermore, this session will highlight one of the report's most startling conclusions: that newer, more "performant" models can introduce regressions, such as a higher frequency of severe bugs and vulnerabilities. This counterintuitive finding underscores the hidden risks associated with model upgrades and challenges the industry's reliance on performance as the sole metric for advancement.

Attendees will leave with a new, more nuanced framework to move beyond the hype of benchmark scores and make informed decisions that account for the long-term benefits, cost, and risk associated with AI-generated code.