RAG¶

Hybrid RAG : BM25 + Vector Search With +10% Recall

Your vector RAG is missing questions you don't even know about

It's a comment I hear often on RAG projects: "It works well in general, but sometimes it finds nothing on questions that seem straightforward."

Concrete example: "What is the ISO-27001 procedure for remote access?" → 0 relevant results.

Vector search encodes meaning. But when a query contains an exact identifier — a standard name, a product code, a domain acronym — semantic encoding fails completely.

This is what's called vocabulary mismatch. And it's the problem hybrid search solves.

The 5 Most Common RAG Mistakes

Introduction

Since 2023, I've run about ten RAG projects myself and led another ten with teams. Some went very well, others less so, but we always tried to learn and correct course along the way. Looking back, I keep seeing the same mistakes, whether from myself early on, from clients, or from peers. These aren't technical mistakes (I cover those in this article), they're mistakes of posture, approach, and method.

Everyone makes them at least once. The point here is to name them clearly so they don't get repeated.

RAG vs Long Context LLM: Is RAG Really Dead?

Introduction: RAG, a magic method?

Every time a new model launches with a larger context window, people announce that RAG is obsolete. Yet RAG was born out of a very concrete need: you cannot hand a 400 or 500-page document to an LLM and ask it questions on the spot.

In enterprise settings, you often have dozens (or even hundreds) of files. RAG offers a simple answer: build a document base out of small pieces (chunks), then dynamically supply the relevant chunks to the AI with each question.

4 Technical Causes of RAG Failure (and How to Fix Them)

Introduction

A "basic" RAG is quick to set up, but it often plateaus between 50 and 70% correct answers. In a business context, that's not good enough for reliable use.

If you're looking for an error analysis method to prioritize improvement actions, the dedicated article is here:
My RAG isn't working: why error analysis changes everything

If you want to first understand why RAG remains useful despite large context windows, I have a dedicated article:
Is RAG really dead?

Here, we focus on the other question: why a RAG doesn't answer correctly, and how to improve it.