Code Quality Design Help

Responsible AI-Assisted Development: Maintaining Code Quality with LLM Tools

AI-powered coding assistants like GitHub Copilot have transformed software development, offering significant productivity gains but introducing a hidden cost: technical debt. While developers can accomplish tasks faster than ever, industry research reveals a concerning pattern of quality degradation. This guide provides evidence-based practices to harness AI's power while maintaining professional code quality standards. Vellum AI's 2025 leaderboard confirms capability varies by model; Evidently AI's July 2025 roundup of 15 benchmarks (212 challenges) underscores rigorous evaluation complexity (Vellum AI, 2025; Evidently AI, 2025).

Recent studies quantify this productivity paradox:

Gains:

  • 55% productivity increase with GitHub Copilot (GitHub, 2024).[5]

  • 85% of developers felt more confident in code quality.[5]

  • Code reviews finished 15% faster.[5]

  • 88% of developers stayed in flow while using the assistant.[5]

Costs - Code Quality Degradation:

  • Code duplication rising: 8.3% → 12.3% (GitClear 2025, 211M LOC analysis).[6]

  • Refactoring activity declining: 25% → <10% of code changes (indicating less code improvement and cleanup).[6]

  • Code churn doubling: 2x increase in code that gets revised or deleted within two weeks.[6]

  • 4x increase in code cloning, signaling mounting duplication debt.[6] GitClear's analysis shows "copy/pasted" code rose from 8.3% to 12.3% between 2021-2024, while "copy/paste" exceeded "moved" code for the first time in history, indicating developers are duplicating rather than reusing existing code.[6]

  • System stability declining: 7.2% decrease (Google DORA 2024).[7]

  • Routine defects in AI-generated code: A July 2025 arXiv survey (447 papers screened, 100 core studies retained) found code generation agents routinely ship logical defects, performance pitfalls, and security vulnerabilities that unit tests often miss, forcing developers to invest extra review effort (Dong et al., 2025).[8]

Risks in Brownfield Systems:

  • MIT Sloan 2025 warns that rapidly layering AI-generated code onto existing (brownfield) systems compounds technical debt, especially with less-experienced developers.[1]

  • Common problems include tangled dependencies, integration conflicts, and hidden debt that outpaces short-term productivity gains.[1]

This occurs because AI optimizes for speed and pattern matching, not software design principles. The result is functional code that works initially but becomes difficult to maintain.

Why AI Tools Produce Mediocre Code

Large language models (LLMs) are sophisticated prediction engines trained on massive datasets of existing code. Understanding their fundamental limitations explains why they produce problematic code:

Mathematical Mediocrity

LLMs predict the next token based on probability distributions from training data, producing outputs that reflect the most statistically likely patterns rather than optimal designs. This causes them to generate code that looks like the statistical average of what they have seen, gravitating toward common approaches rather than elegant or maintainable solutions (Atomic Object, 2025).[4]

Training Data Quality

The sheer volume of average and mediocre code in training data dominates the signal, creating a regression toward the mean. For every well-designed class following SOLID principles, there are hundreds of examples violating them (Atomic Object, 2025).[4]

The Innovation Gap

AI tools cannot innovate beyond their training data. They manipulate statistical patterns but lack genuine understanding or the ability to challenge fundamental assumptions. True innovation requires questioning existing approaches and imagining entirely new solutions: an LLM trained only on pre-OOP code could never have invented object-oriented programming because it would only reproduce existing patterns. This explains why AI cannot recognize when conventional approaches are flawed and lacks genuine understanding of design patterns (Atomic Object, 2025).[4]

Common Code Quality Issues

SOLID Principle Violations

Research shows LLMs consistently generate code that violates SOLID principles:

  • Single Responsibility Principle (SRP): AI tools frequently generate classes that handle multiple unrelated responsibilities (Pehlivan et al., 2025).[3]

  • Dependency Inversion Principle (DIP): AI consistently creates concrete dependencies instead of relying on abstractions, with some models achieving only 10.8% accuracy in detecting DIP violations (Pehlivan et al., 2025).[3] A 240-example benchmark across CodeLlama, DeepSeekCoder, QwenCoder, and GPT-4o Mini shows prompt strategy drives large swings in accuracy, with even top models still struggling on DIP.[3]

  • Open/Closed & Extensibility: AI-generated code often violates the Open/Closed Principle by creating rigid structures that are hard to extend without modification. Developers must actively refactor AI output to ensure code can be extended without modifying existing logic.[2]

  • Refactoring Discipline: brgr.one stresses scheduling refactors of AI-generated classes to split overloaded responsibilities, replace concrete dependencies with abstractions, and add tests that enforce interface segregation before merging.[2]

Procedural vs. Functional Programming

In my experience, AI tools tend to generate more procedural-style code rather than functional programming approaches. Functional programming, with its emphasis on immutability and pure functions, requires explicit guidance and refactoring.

Disciplined Development Practices

Work in Small Increments

Generate small, focused code segments and pause after each one for a quick review. This prevents technical debt from accumulating by catching obvious issues, such as oversized classes, long methods, or poor testability, before they become integrated into the codebase. A 2025 review reveals LLM code generation gaps in ethics and maintainability, emphasizing essential human oversight as AI often overlooks architectural maintainability constraints.[9]

Demand Testability

Explicitly instruct AI that all generated code must be testable. This drives better design decisions by forcing the use of dependency injection and avoiding hardcoded dependencies or static method calls. ScienceDirect 2025 found verifying correctness remains challenging as unit tests alone often miss subtle logic errors.[10]

Enforce SOLID Principles and Cohesion

AI will not automatically produce SOLID-compliant code. You must actively enforce these principles to maintain low coupling and high cohesion.

  • Replace direct dependencies with abstractions (interfaces).

  • Use dependency injection patterns consistently.

  • Break up monolithic classes into focused, cohesive units.

  • Verify that classes depend only on abstractions, not concrete implementations.

Prefer Functional Programming Patterns

Explicitly request functional approaches. Use immutable data structures, favor pure functions, and employ LINQ and functional pipelines.

public sealed record ServerCredential(string Username, string Password); public Result<ServerCredential> TryGet() { var opts = _options.Value; return Result.Success(opts) .Ensure(_ => IsEnabled, "Server credentials are not enabled.") .Ensure(_ => File.Exists(opts.UsernamePath!), $"Username file not found at '{opts.UsernamePath}'.") .Ensure(_ => File.Exists(opts.PasswordPath!), $"Password file not found at '{opts.PasswordPath}'.") .Bind(_ => ReadCredentials(opts)) .TapError(error => _logger.LogInformation( "Server credentials not used: {Error}", error)); }

Keep Methods Small and Focused

Break AI-generated "God methods" into focused, single-purpose functions, aiming for methods under 10-15 lines.

Implementation Strategy

Development Workflow

  1. Generate: Use AI for initial code generation.

  2. Review: Immediately examine the output for design issues.

  3. Refactor: Transform the code to meet quality standards.

  4. Test: Verify functionality and structural properties.

  5. Iterate: Repeat in small increments.

  6. Govern Usage: MIT Sloan recommends explicit guardrails for when AI code is safe (greenfield/low-risk) versus when to avoid or slow-roll adoption (legacy-heavy/brownfield, junior-heavy teams), to prevent compounding technical debt.[1]

What AI Tools Excel At

  • Generating boilerplate code and standard CRUD operations.

  • Implementing well-understood algorithms.

  • Explaining common programming concepts.

  • Producing competent "average" solutions quickly for typical cases: useful for boilerplate but insufficient for novel architectures or breakthrough designs.[4]

What Requires Human Judgment

  • Designing system architecture and component boundaries.

  • Solving novel problems requiring innovative approaches.

  • Evaluating tradeoffs between design alternatives.

Effective Prompting Strategies

Research shows that different prompting strategies improve output quality (Pehlivan et al., 2025):[3] deliberate ensemble prompts excel at OCP detection while hint-based example prompts improve DIP accuracy, underscoring the need to match prompt style to the design smell you are targeting.[3]

Guardrails for Trust and Transparency

  • Only 24% of DORA 2024 respondents trust AI-generated code “a lot,” and many report limited transparency on how AI is applied in their toolchains; make trust and explainability explicit acceptance criteria when adopting AI in delivery pipelines.[7]

  • AI usage is rising across IDEs and internal web tools, but half of teams still avoid automated AI steps in their CI/CD; pilot with clear rollback plans before expanding automation surfaces.[7]

  • Direct prompts work well for SRP and ISP.

  • Example-based prompts significantly improve detection of LSP and DIP violations.

Key Takeaways

  1. AI tools are pattern-driven, not principle-driven.

  2. Training data bias toward mediocrity.

  3. SOLID violations are the norm, not the exception.

  4. Human discipline transforms outputs.

Conclusion

Success with AI coding tools demands a systematic approach: work in small increments, review and refactor immediately, and explicitly enforce design principles. This disciplined methodology combines the productivity benefits of AI with the quality standards necessary for maintainable software. Lunabase.ai October 2025 emphasizes production code must meet rigorous maintainability standards: shortcuts undermine project health.

Further Reading

References

  1. MIT Sloan Management Review - "The Hidden Costs of Coding with Generative AI" (August 2025)

  2. brgr.one - "Keep Your Code SOLID in the Age of AI Copilots" (November 2024)

  3. arXiv - Pehlivan, F., et al. "Are We SOLID Yet? An Empirical Study on Prompting LLMs to Detect Design Principle Violations" (September 2025)

  4. Atomic Object - "Large Language Models Are Designed to Be Average" (August 2025)

  5. GitHub - Research on GitHub Copilot productivity impacts (2024)

  6. GitClear - "2025 State of AI-Affected Code Quality" (analysis of 211M LOC, 2020-2024)

  7. Google DORA - DevOps Research and Assessment reports (2024)

  8. arXiv - Dong, Y., et al. "A Survey on Code Generation with LLM-based Agents" (July 2025)

  9. Springer - "Usage of LLM for Code Generation Tasks" (2025)

  10. ScienceDirect - "Correctness assessment of code generated by LLMs" (2025)

04 December 2025