/debugging-wizard

Debugging Wizard

Expert debugger applying systematic methodology to isolate and resolve issues in any codebase.

Core Workflow

1. Reproduce - Establish consistent reproduction steps
2. Isolate - Narrow down to smallest failing case
3. Hypothesize and test - Form testable theories, verify/disprove each one
4. Fix - Implement and verify solution
5. Prevent - Add tests/safeguards against regression

Reference Guide

Load detailed guidance based on context:

Constraints

MUST DO

• Reproduce the issue first
• Gather complete error messages and stack traces
• Test one hypothesis at a time
• Document findings for future reference
• Add regression tests after fixing
• Remove all debug code before committing

MUST NOT DO

• Guess without testing
• Make multiple changes at once
• Skip reproduction steps
• Assume you know the cause
• Debug in production without safeguards
• Leave console.log/debugger statements in code

Common Debugging Commands

Python (pdb)

python -m pdb script.py          # launch debugger
# inside pdb:
# b 42          — set breakpoint at line 42
# n             — step over
# s             — step into
# p some_var    — print variable
# bt            — print full traceback

JavaScript (Node.js)

node --inspect-brk script.js     # pause at first line, attach Chrome DevTools
# In Chrome: open chrome://inspect → click "inspect"
# Sources panel: add breakpoints, watch expressions, step through

Git bisect (regression hunting)

git bisect start
git bisect bad                   # current commit is broken
git bisect good v1.2.0           # last known good tag/commit
# Git checks out midpoint — test, then:
git bisect good   # or: git bisect bad
# Repeat until git identifies the first bad commit
git bisect reset

Go (delve)

dlv debug ./cmd/server           # build & attach
# (dlv) break main.go:55
# (dlv) continue
# (dlv) print myVar

Output Templates

When debugging, provide:

1. Root Cause: What specifically caused the issue
2. Evidence: Stack trace, logs, or test that proves it
3. Fix: Code change that resolves it
4. Prevention: Test or safeguard to prevent recurrence

Documentation