Read-only root-cause diagnosis for a symptom, bug, failure, or unexpected behavior. Establishes the mechanism at file:line and reads up the facts instead of guessing, before any fix is attempted. Produces a diagnosis report; the fix is always a separate step gated by an explicit GO. Use when something is broken, failing, throwing, or behaving unexpectedly and the cause is not yet proven, or when asked to investigate or find the root cause. Not for judging whether finished work meets its requirement (use audit) and not for confirming rendered UI behavior (use verify).
How to install diag?
marcel-bich/marcel-bich-claude-marketplace/diag
$npx -y skills add marcel-bich/marcel-bich-claude-marketplace --skill diagInstalls into the current project.
›Prefer a prompt? Paste this to your agent
Run `npx skills use "https://github.com/marcel-bich/marcel-bich-claude-marketplace" --skill "marcel-bich/marcel-bich-claude-marketplace/diag"` and follow the generated skill instructions now. Read its complete output, redirecting it to a temporary file first if necessary. Resolve relative paths from the supporting-files directory it provides.
Use the skills in "https://github.com/marcel-bich/marcel-bich-claude-marketplace" that are relevant to the current task. Run `npx skills add "https://github.com/marcel-bich/marcel-bich-claude-marketplace"` and select the relevant skills, then follow their instructions.
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