Coding & Development tag | eYssen AI

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Project Instructions an Agent Actually Follows

Krisztian Eyssen, Krisztian Eyssen

Project Instructions an Agent Actually Follows

In a paired experiment, a project instruction file meant **20% fewer tokens and 20% less time** for the same task. What nobody has demonstrated is that it makes the code better. And there is a ceiling: **at roughly eighty simultaneous rules**, "follows every rule" essentially stops happening.

Advanced Developer How-To Coding & Development

Sep 13, 2026

Reviewing AI-Written Code: What to Look For

Krisztian Eyssen, Krisztian Eyssen

Reviewing AI-Written Code: What to Look For

Since 2023 the share of generated code that compiles has climbed from 50% to 95%. Over the same period the security rate **stayed between 45% and 55%**. The defects did not disappear, they moved house: permissions and architecture took the place of typos. Review has to follow them.

Intermediate Developer How-To Coding & Development

Sep 13, 2026

The Security Bill of AI-Generated Code

Krisztian Eyssen, Krisztian Eyssen

The Security Bill of AI-Generated Code

From 11 September 2026, anyone placing software on the market in the European Union **has to report an actively exploited vulnerability within 24 hours**. Meanwhile roughly **45%** of generation tasks produce code with a known vulnerability when there is no explicit security instruction. Those two numbers together are the bill.

Advanced Developer Explainer Coding & Development

Sep 13, 2026

Hallucinated Packages: When AI Invents a Library

Krisztian Eyssen, Krisztian Eyssen

Hallucinated Packages: When AI Invents a Library

**43%** of invented package names come back identically in all ten runs out of ten. That is what turns a hallucination into an attack surface: the attacker does not have to guess what the model will invent — one question is enough. A documented, successful attack, on the other hand, **had not happened** by mid-2026 — and that honest answer is stronger than scaremongering.

Advanced Developer Troubleshooting Coding & Development

Sep 13, 2026

Tests First: Building the Safety Net with AI

Krisztian Eyssen, Krisztian Eyssen

Tests First: Building the Safety Net with AI

Out of a hundred generated tests, **eighteen** stayed usable in an industrial-scale system. And there is a surprising split: **a test you hand the model in the prompt improves the result by 7–30% — a test the agent writes for itself improves it by practically nothing.** The difference between the two is who gets to say what "correct" means.

Intermediate Developer How-To Coding & Development

Sep 13, 2026

Understanding a Legacy Codebase with AI

Krisztian Eyssen, Krisztian Eyssen

Understanding a Legacy Codebase with AI

Model performance **falls off sharply above 32,000 tokens** — while the context window they advertise runs from 128,000 to a million. And there is a measured bias: ask how the repo is put together, and the model would rather **rewrite** it than understand it. This post is about how to ask so that does not happen.

Intermediate Developer Recipe Coding & Development

Sep 13, 2026

Documentation You Will Actually Maintain

Krisztian Eyssen, Krisztian Eyssen

Documentation You Will Actually Maintain

Two independent measurements say the same thing, and both contradict received wisdom: **bad documentation is measurably worse than none**, and the machine-generated "repo tour" **lowered the success rate while making runs 20–23% more expensive**. This post is about what survives all that — not much, but it works.

Intermediate Developer Recipe Coding & Development

Sep 13, 2026

Debugging with AI: A Reproducible Method

Krisztian Eyssen, Krisztian Eyssen

Debugging with AI: A Reproducible Method

On a synthetic, self-contained bug, models get the location right 38–53% of the time. In a real repository, **from the code alone, 1–5%.** The text of the bug report on its own is worth six to thirteen points, and the **order** of the input as much as thirty-seven. This post is about how you hand the bug over.

Intermediate Developer Troubleshooting Coding & Development

Sep 13, 2026

Vibe Coding: What It Is Good For and Where It Stops

Krisztian Eyssen, Krisztian Eyssen

Vibe Coding: What It Is Good For and Where It Stops

By the original definition, the point of vibe coding is that you "**forget that the code even exists**". So the question is not how good the model is — it is whether **you can afford to forget that this particular code exists**. In nine documented cases the answer was no.

Beginner Business owner Explainer Coding & Development

Sep 13, 2026

From Prototype to Production: The 70% Wall

Krisztian Eyssen, Krisztian Eyssen

From Prototype to Production: The 70% Wall

There is **no measurement** behind the famous "70%" — the author himself writes that he took it from a tweet. What has been measured: **37%** of companies can show any bottom-line effect at all from AI, and that share has **not moved** in a year — while 80% feel personally more productive. That is the wall.

Intermediate Business owner Explainer Coding & Development

Sep 13, 2026

AI in Code Review: Which Bots Are Worth It

Krisztian Eyssen, Krisztian Eyssen

AI in Code Review: Which Bots Are Worth It

In an independent measurement, the precision of AI review agents is **3.2–5.1%** — roughly one comment in twenty lands. In a peer-reviewed vendor study, meanwhile, **38.7%** of the comments triggered a code change and PR turnaround got **30.8%** shorter. Both are true. They are not measuring the same thing — and that is what this post is about.

Advanced Developer Tool review Coding & Development

Sep 13, 2026

DevOps and Infrastructure with AI

Krisztian Eyssen, Krisztian Eyssen

DevOps and Infrastructure with AI

The same model that solves 86% of Python tasks manages barely a **fifth** of infrastructure-as-code tasks. And there is a measurement that took the result from 14% to **93%** — of the 79-point gain, **48.9 points** came from retrieved documentation, prompt structure and the scanner's feedback, **21.5 points** from switching models, and **8.6 points** from letting the model **see the rule**.

Advanced Developer How-To Coding & Development

Sep 13, 2026

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