No feature is guaranteed to be bug-free on the first try - and the new search feature from the last chapter actually has a small bug. While testing, you notice: recipes with the ingredient " tomato" (with a leading space, because a space was accidentally typed in while adding it) don't show up when searching for "tomato", even though they should. This chapter shows how to describe such a bug so Claude Code can pinpoint it reliably.

Why the bug description matters so much

Just like with a feature prompt: the more specific the description, the more targeted the debugging. A bug report especially benefits from four pieces of information: what you expected, what actually happened, how to reproduce it, and - if available - the exact error message.

A poor bug description

> The search doesn't work right.

This description forces Claude Code to hunt down the bug itself before fixing can even begin - that costs time and might target the wrong issue if there are several small rough edges in the code.

A good bug description

> Bug in the ingredient search: a recipe with the ingredient " tomato" (with a leading space) is NOT found when searching for "tomato", even though it should be. Expected: the search should ignore leading/trailing spaces on ingredients. Likely affected: the GET /api/recipes route in server.js.

This version names the exact reproduction case (which ingredient, which search term), the expected behaviour, and even a guess at where the bug might be. Claude Code can then look straight at server.js, understand the bug, and fix it in a targeted way.

The fix

The cause: the comparison ingredient.toLowerCase().includes(searchTerm) handles case, but not extra whitespace. The fix is a small, targeted Edit change:

const filtered = recipes.filter((recipe) =>
  recipe.ingredients.some((ingredient) =>
    ingredient.trim().toLowerCase().includes(searchTerm)
  )
);

A single extra method (.trim()), in exactly the right spot - possible because the bug description was precise enough to find the cause without detours.

Making a bug reproducible for Claude Code

For more complex bugs, it also helps to have Claude Code reproduce the bug itself before fixing it - for example with a targeted curl call or a small test script. That way the bug is first confirmed objectively, and after the fix the same call can immediately verify whether it's actually gone.

The next chapter takes this one step further: instead of waiting for a concrete bug, you'll have Claude Code actively review existing code and improve it - a code review.