Debugging Mindset — The Quiet Superpower

Skipping any step is how you waste an afternoon. Especially the first one.

• Reproduce minimally. Smallest input that triggers the bug. Half the bugs solve themselves once you reproduce them in isolation.
• Bisection. "When did this break?" → git bisect. "Which input causes it?" → binary-search the data.
• Read the actual error. The first stack frame and the last line are usually the answer. People skip-read and miss it.
• Print is fine. A well-placed log line beats an hour with a debugger you barely know.
• Debugger when state is the problem. Step through; inspect; conditional breakpoints.
• Diff against working. What's different between the broken case and the last known good?
• Rubber duck. Explaining out loud surfaces the assumption you didn't know you were making.

• Changing two things at once. Now you don't know which fix worked.
• Believing it must be the framework. 99% of the time, it's your code.
• Trusting the comment. Comments lie. The code is the truth.
• Assuming the logs are right. Sometimes the logger itself is broken.
• Heisenbugs. Bugs that disappear when observed — usually a race or timing issue. Add logging, don't remove it.
• Confirmation bias. You stop looking when you've found a cause; not the cause.

• Write the failing test first. Then make it pass with the fix. Now it can't regress.
• Note the root cause in the PR or commit message — future you will thank current you.
• Ask "what made this hard to find?" Better logs, better tests, better assertions next time.
• Look for siblings. The same bug pattern often hides elsewhere in the codebase.
• Five Whys on serious incidents — the surface symptom is rarely the cause.

• Sunk-cost debugging. If you've spent two days, sometimes the right move is to revert and start clean.
• Asking too late. A 20-minute "what am I missing?" with a colleague beats a 4-hour solo descent.
• "Works on my machine" theatre. Reproduce in the broken environment, not yours.
• Tired debugging. After 90 minutes of staring, sleep on it. Mornings find bugs evenings can't.