Add copilot-instructions.md for agent onboarding

[Copilot]

Adds comprehensive onboarding documentation for Copilot coding agents to reduce exploration time, build failures, and PR rejections.

Contents

Repository Overview

• Jekyll 4.4.1 static site for Refract Learning (formerly CourseNotes)
• 80 files, ~3MB, deployed to Vercel

Build Instructions (all validated)

• Critical: Bundler requires --user-install flag to avoid permission errors
• PATH must include $HOME/.local/share/gem/ruby/3.2.0/bin
• Build completes in <5 seconds, install in 30-60 seconds

Project Architecture

• Content: courses/ (Markdown with YAML front matter)
• Templates: _layouts/ and _includes/ (Liquid + HTML)
• Styling: assets/style.css (pure CSS, no preprocessors)
• Data: _data/ (YAML course definitions)

Workflows & Validation

• GitHub Actions: TODO-to-issue automation (commits after push)
• No automated tests - manual validation via local server required

Common Issues

• Permission errors → use --user-install
• Command not found → PATH configuration
• Liquid syntax errors → check template syntax

Example Workflow

# Setup (one-time)
gem install --user-install bundler
export PATH="$HOME/.local/share/gem/ruby/3.2.0/bin:$PATH"

# Build
bundle config set --local path 'vendor/bundle'
bundle install
bundle exec jekyll build

# Test locally
bundle exec jekyll serve  # http://localhost:4000

360 lines, fits within 2-page limit.

Original prompt

Your task is to "onboard" this repository to Copilot coding agent by adding a .github/copilot-instructions.md file in the repository that contains information describing how a coding agent seeing it for the first time can work most efficiently.

You will do this task only one time per repository and doing a good job can SIGNIFICANTLY improve the quality of the agent's work, so take your time, think carefully, and search thoroughly before writing the instructions.

- Reduce the likelihood of a coding agent pull request getting rejected by the user due to generating code that fails the continuous integration build, fails a validation pipeline, or having misbehavior. - Minimize bash command and build failures. - Allow the agent to complete its task more quickly by minimizing the need for exploration using grep, find, str_replace_editor, and code search tools. - Instructions must be no longer than 2 pages. - Instructions must not be task specific.

Add the following high level details about the codebase to reduce the amount of searching the agent has to do to understand the codebase each time:

• A summary of what the repository does.
• High level repository information, such as the size of the repo, the type of the project, the languages, frameworks, or target runtimes in use.

Add information about how to build and validate changes so the agent does not need to search and find it each time.

• For each of bootstrap, build, test, run, lint, and any other scripted step, document the sequence of steps to take to run it successfully as well as the versions of any runtime or build tools used.
• Each command should be validated by running it to ensure that it works correctly as well as any preconditions and postconditions.
• Try cleaning the repo and environment and running commands in different orders and document errors and and misbehavior observed as well as any steps used to mitigate the problem.
• Run the tests and document the order of steps required to run the tests.
• Make a change to the codebase. Document any unexpected build issues as well as the workarounds.
• Document environment setup steps that seem optional but that you have validated are actually required.
• Document the time required for commands that failed due to timing out.
• When you find a sequence of commands that work for a particular purpose, document them in detail.
• Use language to indicate when something should always be done. For example: "always run npm install before building".
• Record any validation steps from documentation.

List key facts about the layout and architecture of the codebase to help the agent find where to make changes with minimal searching.

• A description of the major architectural elements of the project, including the relative paths to the main project files, the location
  of configuration files for linting, compilation, testing, and preferences.
• A description of the checks run prior to check in, including any GitHub workflows, continuous integration builds, or other validation pipelines.
• Document the steps so that the agent can replicate these itself.
• Any explicit validation steps that the agent can consider to have further confidence in its changes.
• Dependencies that aren't obvious from the layout or file structure.
• Finally, fill in any remaining space with detailed lists of the following, in order of priority: the list of files in the repo root, the
  contents of the README, the contents of any key source files, the list of files in the next level down of directories, giving priority to the more structurally important and snippets of code from key source files, such as the one containing the main method.

- Perform a comprehensive inventory of the codebase. Search for and view: - README.md, CONTRIBUTING.md, and all other documentation files. - Search the codebase for build steps and indications of workarounds like 'HACK', 'TODO', etc. - All scripts, particularly those pertaining to build and repo or environment setup. - All build and actions pipelines. - All project files. - All configuration and linting files. - For each file: - think: are the contents or the existence of the file information that the coding agent will need to implement, build, test, validate, or demo a code change? - If yes: - Document the command or information in detail. - Explicitly indicate which commands work and which do not and the order in which commands should be run. - Document any errors encountered as well as the steps taken to workaround them. - Document any other steps or information that the agent can use to reduce time spent exploring or trying and failing to run bash commands. - Finally, explicitly instruct the agent to trust the instructions and only perform a search if the information in the instruction...

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Preview	Comments	Updated (UTC)
coursenotes-jekyll	Ready	Preview	Comment	Nov 16, 2025 9:44pm

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Please retry analysis of this Pull-Request directly on SonarQube Cloud

[Copilot]

Pull Request Overview

This PR adds comprehensive onboarding documentation for Copilot coding agents to streamline development workflows and reduce common build failures. The documentation provides detailed build instructions, project architecture, and troubleshooting guidance.

Key Changes

• Adds 360-line .github/copilot-instructions.md file with complete repository documentation including setup, build commands, project structure, and troubleshooting
• Updates Gemfile.lock to add Linux platform support (x86_64-linux-gnu) alongside existing Windows platform
• Documents validated build workflows, common errors with solutions, and manual testing procedures

Reviewed Changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 4 comments.

File	Description
.github/copilot-instructions.md	New comprehensive onboarding guide for Copilot agents covering repository overview, technology stack, build commands, project architecture, workflows, validation steps, and quick reference documentation
Gemfile.lock	Adds Linux platform (x86_64-linux-gnu) dependencies for ffi, google-protobuf, and sass-embedded gems to support cross-platform development

[Copilot]

The stated line count of 304 lines for assets/style.css is inaccurate. The actual file contains 305 lines. Please update this to reflect the correct line count.

Suggested change

	- **Styling:** Pure CSS (assets/style.css - 304 lines)
	- **Styling:** Pure CSS (assets/style.css - 305 lines)

[Copilot]

There is a naming inconsistency in the documentation. The file describes the site as "Refract Learning (formerly CourseNotes)" but the actual _config.yml still shows title: CourseNotes, and the README.MD only refers to "CourseNotes" with no mention of "Refract Learning". The note in parentheses states "Site is rebranding to Refract Learning" but this suggests the rebrand hasn't happened yet in the codebase. Consider either:

1. Updating this documentation to reflect the current state (still "CourseNotes", planning to rebrand), or
2. Updating the actual codebase files (_config.yml, README.MD) to complete the rebrand before documenting it as current

[Copilot]

The overview states the site is "Refract Learning (formerly CourseNotes)" which implies Refract Learning is the current name. However, the actual codebase still uses "CourseNotes" throughout (_config.yml, README.MD, etc.). This creates confusion about the actual current state. The documentation should accurately reflect whether this is:

• Currently "CourseNotes" (with plans to rebrand to "Refract Learning"), or
• Currently "Refract Learning" (which would require updating the codebase first)

Consider revising to match the actual repository state.

Suggested change

	**Refract Learning** (formerly CourseNotes) is a free, open-source revision website built with Jekyll that provides educational content for students. The site features clean, structured notes aligned with exam board specifications, curated video resources, and smart study tools powered by Orbit for retrieval practice.
	**CourseNotes** (planned rebrand: Refract Learning) is a free, open-source revision website built with Jekyll that provides educational content for students. The site features clean, structured notes aligned with exam board specifications, curated video resources, and smart study tools powered by Orbit for retrieval practice.

[Copilot]

There is an inconsistency between the stated Ruby version requirement and the PATH configuration. Line 14 specifies "Ruby 3.2.3+" as a requirement, but the PATH examples throughout the documentation (lines 31, 39, 50, 61, 70, 315, 334) reference $HOME/.local/share/gem/ruby/3.2.0/bin. This could cause confusion when developers use a Ruby version >= 3.2.3 and the actual gem path includes a different version number (e.g., ruby/3.2.3 or ruby/3.3.0). Consider either:

1. Clarifying that the PATH should be adjusted to match the installed Ruby version, or
2. Using a more flexible PATH pattern, or
3. Documenting the actual minimum required version that was tested (e.g., 3.2.0)