Pet peeves with GitHub Copilot Instructions and my solution

Pet peeves with GitHub Copilot Instructions and my solution

Claude Code's .claude/rules/ feature allows creating custom markdown files with instructions for the model. This feature is advantageous as it lets developers include specific rules for certain codebases while omitting irrelevant guidance. This saves input tokens and improves agent performance.

However, GitHub Copilot has its own format for custom instructions, located in .github/instructions/*.instructions.md. The format requires a single string property called applyTo instead of the paths property used in Claude Code. If a Copilot instructions file needs to reference multiple patterns, this becomes cluttered and unreadable.

To add to the frustration, Claude Code supports a @path/to/file syntax that allows referencing other files in the project's context at launch. This can be useful when there are pre-existing project documentation files that are not directly related to the AI-assisted development rules. This feature is missing from GitHub Copilot's instructions format.

One client I work with operates in a restricted security environment, only allowing GitHub Copilot access through the CLI, VSCode, or IntelliJ plugins. While they appreciate the cross-compatibility of Copilot with Claude rules, they encountered a limitation - the missing @import syntax in Copilot instructions. This feature would have been helpful for loading referenced files and integrating with Backstage for generating online wikis.

The workaround I implemented was to create a Node.js script that parses through instruction files, searching for patterns like !-- @import path/to/file -- and replacing them with the referenced contents. By using HTML comments, the script avoids interfering with the LLM's processing. This solution lets me author my instruction files with the desired @import syntax while avoiding redundancy in the documentation.