Claude Code Bug Report Template: Turn Vague Errors Into Reproducible Fixes

Most Claude Code debugging sessions fail before the model even sees the real problem

When someone says “Claude Code could not fix it,” the root cause is often not model quality. It is input quality. A vague bug report produces vague debugging. A reproducible bug report gives Claude Code something concrete to reason about.

This template is for the gap between random failure and a real fix. It pairs well with Claude Code Debugging Techniques and the review discipline in Claude Code Code Review Checklist.

What a useful bug report must contain

Claude Code does better when the bug report includes:

Field	Why it matters
Symptom	What the user actually sees
Expected result	What should have happened instead
Reproduction steps	How to make the bug happen again
Scope	Which page, command, or route is affected
Evidence	Logs, screenshots, stack traces, or failing tests
Recent changes	What changed before the bug appeared

Without those fields, the agent spends half its context guessing.

Copy-paste bug report template

# Bug report

## Symptom
- What broke?
- Where did it break?

## Expected result
- What should have happened?

## Reproduction steps
1. ...
2. ...
3. ...

## Evidence
- error message:
- screenshot:
- related logs:

## Suspected area
- file or route:
- recent change:

## Constraints
- do not touch:
- allowed commands:

This is not paperwork. It is a forcing function for better debugging.

Turn the template into an agent-ready prompt

Once the note is filled, ask Claude Code for analysis before a fix.

Read this bug report.
1. identify the most likely cause
2. rank the top 3 hypotheses
3. tell me the smallest command or file read that would disprove each one
4. do not patch yet

That prompt prevents the common failure mode where the model edits code before proving the problem.

Three real examples

Example 1. Frontend layout bug

Bad report:

The mobile page is broken.

Better report:

Symptom: CTA buttons overlap on iPhone width at /en/products/
Expected: buttons stack vertically without clipping
Reproduction: open /en/products/ at 390px width
Evidence: screenshot + scrollWidth is 412
Recent change: pricing card copy expanded yesterday

Now Claude Code can inspect the exact layout risk.

Example 2. API 500 error

Bad report:

Checkout endpoint fails.

Better report:

Symptom: POST /api/checkout returns 500
Expected: returns 200 with payment URL
Reproduction: send payload with plan=pro
Evidence: stack trace mentions undefined env var
Recent change: moved Stripe config to a new module

Example 3. Build failure

Bad report:

Build is red.

Better report:

Symptom: npm.cmd run build fails in site/
Expected: Astro build completes
Evidence: error points to missing frontmatter field in one locale
Recent change: published new multilingual article

That report immediately narrows the search surface.

A small evidence collection checklist

Before you ask Claude Code to fix anything, collect:

1. the exact error text
2. the smallest reproduction path
3. the files most likely involved
4. the last known good change

git status --short
git diff --stat
rg -n "ERROR|Error|Exception|failed" logs site/src

These commands often reveal whether the bug is new, localized, or environmental.

Failure modes to avoid

Failure 1. Hiding the expected result

If Claude Code only sees “it failed,” it cannot tell whether success means a new response code, a visual fix, or a safer workflow.

Failure 2. Including secrets in the report

Do not paste API keys, production tokens, or raw customer data into the note. Summarize safely.

Failure 3. Mixing multiple bugs into one report

One report should describe one primary failure. If you bundle five unrelated errors together, the analysis becomes shallow.

Failure 4. Asking for a patch before narrowing scope

Good debugging is not “fix first, inspect later.” It is inspect, rank, prove, then patch.

How this improves team speed, not just one session

A strong bug report helps in three ways:

• Claude Code gets better input
• another human can reproduce the issue
• the final fix becomes easier to review

That is why a bug report template is not only for support or QA teams. It is also a debugging accelerator for developers.

What to save after the fix

Once the bug is resolved, record:

1. the true root cause
2. the proof that the fix worked
3. the rule that should stop the bug from recurring

That last step is often a better investment than the fix itself. It turns one solved bug into a stronger workflow.

Which next step fits this article

Use this ladder:

1. Start with the free cheatsheet if the issue is still basic command fluency.
2. Buy 50 Battle-Tested Claude Code Prompt Templates if you want stronger debugging, triage, and review prompts you can reuse immediately.
3. Check the products page if you want deeper debugging material such as the upcoming error dictionary.
4. Use the consultation page if the real problem is repeated workflow failure across a team, not one isolated bug.

That keeps debugging work tied to proof, not to random prompt experiments.