Buglyst Blog
Learn to debug under pressure.
Playbooks for fast pattern recognition, guides for the full investigation, and articles for the engineering judgment around the edges.
17 playbooks · 509 guides · 95 articles · 12 linked practice labs ·skip to practice
Fast pattern recognition for the production failures engineers see most often.
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Structured investigations for the failure modes engineers meet in real systems.
Works locally but fails in production: how to debug it
Your code runs fine on your machine but breaks the moment it hits staging or production. Here is a structured approach to find the gap.
Feature flag bug: how to debug unexpected feature flag behaviour
A feature flag is supposed to be off for some users but is on for everyone, or vice versa. The flag value, targeting rules, or flag evaluation is wrong.
Redirect URL wrong in production: how to debug redirect bugs
Your app redirects users to `http://localhost:3000/dashboard` in production. The redirect URL is hardcoded, or the origin detection is picking up the wrong value.
Production-only bug: a systematic debugging checklist
A bug only appears in production. You cannot reproduce it locally. Here is a systematic checklist to find environment-specific failures.
Tracking Down Race Conditions in JavaScript Async Logic
Diagnose and fix tricky race conditions in JavaScript asynchronous code—beyond textbook theory. Get actionable steps, examples, and real-world guidance.
Diagnosing `ref.current` Is Null in React
A practical guide to tracing and fixing cases where a React ref's `current` is unexpectedly null, including async pitfalls and strict mode quirks.
Long-form thinking on debugging habits, observability, and the systems around the bug.
5 Questions to Ask Yourself Before Filing a Bug Report
A senior engineer's pre-flight checklist for bug reports — forged in the fire of a production incident that turned a 5-minute fix into a 3-hour hunt.
Binary Search for Bugs: Cutting Down Bisection Time with git bisect run
Automating git bisect with a script turns days of manual hunting into minutes. Here's how to build a reliable bisection harness for your codebase.
Reading a Call Stack: What Each Frame Actually Tells You
A call stack shows you the path your code took to crash. But most developers only look at the top frame. Here’s how to read the whole thing — including async traces, native frames, and minified code.
Using Breakpoints Effectively: Beyond Step and Continue
Most engineers know F9 to set a breakpoint and F5 to run. But breakpoints have hidden superpowers — conditional, logpoint, hit-count, and data breakpoints — that can cut debugging time in half. Here's how to use them with real examples.
Conditional Breakpoints: When and How to Use Them Beyond the Basics
Conditional breakpoints stop only when a specific condition is true, reducing noise in loops and high-frequency code. Here's how to wield them in Chrome DevTools, VS Code, and IntelliJ, plus a war story about a subtle race condition.
Debugging Character Encoding Problems: From Gibberish to Unicode
A practical guide to identifying and fixing character encoding problems, from broken UTF-8 to hidden BOM bytes, with real debugging examples.