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Hey there.

Welcome to Full Stack Focus. 👋 

Here’s everything you need to know this week in the world of full-stack development.

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Programming

📔 What Actually Makes You Senior
This article argues that the real marker of a senior engineer is their ability to reduce ambiguity, not just years of experience or technical skill. While mid-level engineers thrive with clear specs, senior engineers excel when problems are fuzzy, abstract, or poorly defined, turning vague ideas into concrete, shippable plans. The author highlights that this upfront clarification work is often invisible but hugely valuable, preventing surprises and reducing project risk. They also note that many companies fail to hire for this skill, despite it being central to effective engineering leadership.

✏️ Your AI Can’t Read Your Mind: A Simple Guide to Writing CLAUDE.md
This post explains that CLAUDE.md (or AGENTS.md) is the primary way to onboard an LLM agent to your codebase, since models are stateless and know nothing until you tell them. It stresses that a good CLAUDE.md should focus on WHAT the project is, WHY it exists, and HOW to work on it, rather than cramming in every possible command or guideline. The author argues that fewer, universally applicable instructions outperform long, noisy files, and recommends using progressive disclosure: keep detailed, task-specific docs in separate files and just point Claude to them.

😧 How good engineers write bad code at big companies
This article explores why good engineers at big tech companies still produce bad code, arguing the root cause is constant churn: most developers are new to the codebase, the team, or even the language. Because long-term expertise is rare and “old hands” are overloaded, much work is done by relative beginners under deadlines. The author says this is a deliberate tradeoff, companies value mobility and rapid reallocation of talent over code quality. As a result, bad code isn’t incompetence but an inevitable outcome of an environment optimized for flexibility, not craftsmanship.

🎅 Advent of code 2025
Advent of Code 2025 is live, a yearly Advent calendar of small, language-agnostic programming puzzles. The challenges suit all skill levels, used everywhere from interview prep to friendly competitions. You don’t need a CS background, just basic coding and problem-solving skills. Every puzzle is designed to run on even decade-old hardware.

👎️ Google CEO Says AI Coding Can Turn Everyone Into a Developer
Google CEO Sundar Pichai argues that AI will open software development to far more people, calling it one of the most exciting shifts in tech. Central to this is “vibe coding,” where users describe what they want in natural language and AI generates the software. This promises radically broader accessibility, removing the need for deep technical skills. But the vision also sparks tension, as critics warn that AI still oversimplifies the complex engineering required beneath the surface.

🧠 The Math of Why You Can't Focus at Work
This post examines how constant interruptions destroy deep work, updating Paul Graham’s classic argument for the era of Slack, Teams, and nonstop pings. The author notes that focus is clearly collapsing, yet few quantify how bad it’s gotten. They present a mathematical model of interruption-driven work, showing how just three parameters can determine whether a day becomes productive or wasted. By simulating hundreds of days, the post maps out exactly when and why focus breaks down.

Front-End

💼 React Interview Playbook
Front-end interviews are so difficult to prepare for, The industry is shifting away from LeetCode-style DSA questions toward practical UI and front-end implementation tasks, which better reflect real work. But resources for front-end candidates remain scarce, especially for front-end system design. GreatFrontEnd aims to fill this gap by offering targeted lessons, practice problems, study plans, and expert-written solutions tailored specifically to front-end engineers.

🗺️ A complete roadmap to learning React
Everything that is there to learn about React and the ecosystem in 2025.

🎭️ Best practices to consider when building user interfaces
Laws of UX is a collection of best practices that designers can consider when building user interfaces.

👀 The Zero-Width Space-Place
This post introduces the zero-width space (U+200B), an invisible Unicode character that subtly alters how software processes text. The author demonstrates practical and quirky uses, from reordering lists and breaking auto-linking to creating look-alike identifiers in code and triggering Python indentation errors. ZWS can also hide watermarks, enable minimalist social profiles, and control line wrapping in long URLs. The piece highlights how a seemingly “nothing” character can have powerful real-world effects.

AI​

🛍️ ChatGPT Android app 1.2025.329 beta includes new references to an "ads feature" with "bazaar content", "search ad" and "search ads carousel".

🍌 AI Adoption Rates Starting to Flatten Out

😓 OpenAI just revealed that its analytics vendor Mixpanel suffered a security incident, with an attacker exporting some of its API users’ profile information

More Tools & Stories

🔢 Algorithms and data structures implemented in JavaScript with explanations and links to further readings

🥷 CSS components inspired by Final Fantasy

💃 One CSS Trick to Eliminate Scrollbar Layout Shifts

🇦🇺 Australia Spent $62 Million To Update Its Weather Web Site and Made It Worse

Have a great week, see you the same time next week!

- Full Stack Focus team :)