Prompt Tracer

Watch your library think.

Every passage in your library becomes a point on a map, placed by meaning, so related ideas settle into topic clusters. Here you're at the top, speaking a question to the model on the terminal below. Watch it reach out into the clusters, pull in the passages that fit, and answer you on screen — then read on for what happens at each step, and how it scales to your real library.

Ready when you are — press Start the Tour below
↗ Meet the maker · corbet.app

A guided, five-step walk-through — pick your own question or fine-tune it once it's running.

Ask the Prompt Tracer
Speak · 1 / 5

  1. By meaning Formally: vector search.
  2. By keyword Formally: BM25.
  3. Combined Formally: fused ranking.
  4. Reranked Formally: cross-encoder.
  5. Given to the AI Formally: cited answer.

↓  The same five stages, one at a time — no jargon left unexplained

Under the hood

Five stages, one at a time.

The animation moves quickly. Here's what each step is actually doing between the moment you ask and the moment the answer lands — the whole pipeline the Prompt Tracer lights up, unpacked.

01Vector search — retrieval by embedding similarity.

By meaning

Every passage was turned into a string of numbers — an embedding — that captures what it's about, not just its wording. Your question gets the same treatment, and the engine looks for the passages sitting closest to it. That's how it surfaces the right note even when it shares not one word with what you typed.

?
The numbers themselves — each strip is one embedding
Closest on the map = closest in meaning
02BM25 — a classic term-frequency keyword ranker.

By keyword

At the same time, a classic keyword search runs the old-fashioned way. It matches the exact words you used and rewards passages where those words are rare and telling. It's the safety net: if you searched for a specific name, term, or number, the literal hit is never quietly missed.

score
Exact-word hits — the rarer the word, the higher the score
03Fused ranking — reciprocal-rank fusion of the two lists.

Combined

Now there are two ranked lists — one by meaning, one by words. They're blended into a single order, so a passage both lists agree on rises to the top and a one-list fluke sinks. You can even lean the blend toward exact words or toward meaning — that's the knob you turn in the Prompt Lab →

A B C B D A B A C meaning keyword fused
Agreed-on passages (A, B) rise; the fluke (D) drops
04Cross-encoder — a slower model scoring question + passage together.

Reranked

The top handful gets a second, closer read. A slower model looks at your question and each passage together — not as two separate fingerprints — and re-sorts them by how well they actually answer you. It's expensive, so it only runs on the finalists, where it earns its keep.

1 2 3 4 3 1 4 2 first pass reranked
A closer read promotes the passage that truly answers you
05Cited answer — grounded generation with source citations.

Given to the AI

Only the best few passages are handed to the language model, along with your question. It writes an answer grounded in those passages — and every claim carries a citation you can click straight back to the source. Nothing is invented from thin air, and nothing ever leaves your machine.

passage passage passage MODEL [1] [2] answer
A grounded answer — every claim cited, nothing uploaded

At full size

From this miniature to your real library.

What you just drove is a scale model. The map above shows a small sample so the whole thing fits on screen and runs in a browser tab. Point Alambique Index at your own files and the very same machinery runs at full size — on your hardware, with nothing uploaded.

In this demo
  • 240sample passages on the map
  • 6topic clusters
  • 1shared demo library
  • 0installs — it runs in this tab
In your library
  • 1,000sof pages across your PDF documents and personal notes
  • 397of your own files
  • notes, eBooks & PDFs you add
  • 100%on your own machine

The full Prompt Tracer is the app's Observatory — the same living map, rendered from your real index instead of a sample. It's the whole idea of retrieval made visible, at the scale of everything you've saved. Every dot stays on your machine; nothing is ever uploaded.

Get it on GitHub Or drive the Prompt Lab yourself Runs entirely on your Mac or PC using free local AI models — no subscription or command line required