Unlock tedious code migrations with an agent instructions file

What was done

According to an article published on 26 December 2025 on BlaBlaCar's blog, several necessary but boring migrations stagnated for lack of volunteers. The team tested the GitHub agent Copilot on two projects: replacing an old simulation solution from the API (low risk) and rewriting Selenium tests in Playwright (more delicate). After a successful manual trial on an example in VS Code, the task was described in a Copilot prompt file: role, context, precise steps (create branch, migrate file, delete old, declare new routes), search for examples in already labelled pull requests, instructions for shell commands, then create the pull request with a dedicated label. The article insists that the quality of the instructions and the examples condition the quality of the result, and describes a gradual increase in the responsibility entrusted to the agent. He announced that the first assisted migration had been completed.

Before you start

Tool cited by the source: GitHub Copilot. Gather the information the prompt asks for. Strip confidential data that is not needed and check your tool’s access terms. Features and plans can change.

The method, in three steps.

1. 01

   Gather the context

   Gather the information described in the prompt.

2. 02

   Adapt the prompt

   Copy the prompt below, replace the bracketed items, then paste it into GitHub Copilot.

3. 03

   Reread before using

   Reread the result, correct it if needed and keep the final decision. Caveats are detailed below.

Your starting point.

Replace the bracketed items, then adapt the proposal to your situation. This prompt is written by the iadujour desk It is not a quotation from the source.

Role: experienced engineer on
Context: we migrate
Task, for the file I'm telling you:
1. Creates a gird called
2. Migrate the file by inspired sweaters requests labeled
3. Remove the old file and update the references.
4. Opens a pull request with a short title and description.
Ask me for a check instead of running an order you're not sure about.

What deserves your attention

Useful skills

Official skills on the same task, paired by the desk: they are not part of the described case.

• Build an application with SDK GitHub CopilotMicrosoft · Guides the creation of applications that rely on GitHub Copilot via the Copilot SDK, for programmatic integrations in Node.js/TypeScript, Python, Go or .NET: sessions, custom tools, streaming, hooks, MCP servers, BYOK providers, persistence, agents and skills, and deployment schemes.