ghc-prompt-files

Create a file at .github/prompts/<name>.prompt.md with YAML frontmatter specifying mode and description, then write the prompt body with ${input:variableName} placeholders. Invoke it from Copilot Chat by typing /<name> and providing the parameter values when prompted.

Slash commands like /explain or /fix are built-in and fixed. Prompt files are user-defined, version-controlled with the repo, and accept parameters through ${input:...} placeholders. The invocation shape is the same, but ownership and parameterization differ.

Use agent mode when the task requires tools like reading files, writing multiple files, or running commands, such as scaffolding a CLI command with tests. Use edit mode when the result should modify the current file directly, like adding a docstring to a selected function.

VS Code caches the prompt list, so a newly created .prompt.md file may not appear immediately. Restart the Chat session to refresh the picker, and confirm the file lives in .github/prompts/ with the .prompt.md extension.

Use a custom agent when the task needs a persistent persona across a multi-turn conversation, such as an API design reviewer. Prompt files fit one-shot templated tasks; agents fit ongoing roles with sustained context.