Moving business logic from legacy T-SQL stored procedures into C# with Entity
Framework was a long-standing goal for the Petlja.org educational platform,
built on .NET and SQL Server. This talk shares how AI coding agents, primarily
GitHub Copilot, helped make that migration practical and bring the refactored
code into production.

The migration proceeded one method at a time, with database integration tests
checking existing behavior before and after each change. The workflow was
documented in Markdown written for developers, with minimal additional agent
instructions.

The approach supported successful migrations using Claude and GPT models through
GitHub Copilot, as well as Claude Code. A final experiment used Copilot's Bring
Your Own Key support with Qwen3.8-27B-FP8 served through vLLM to migrate news-related
methods. Those migrations took a little longer, but succesfuly.

This final experiment with Qwen suggests that a well-designed AI workflow may not
always require frontier models. For these migrations, the same instructions,
tests, and repository context also supported successful results with a smaller,
self-hosted model.