| # Cento |
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| **A bounded recombinant-memory engine. It composes coherent replies out of *nothing but* the verbatim fragments of a corpus, joined only where the corpus itself licenses the seam. Hallucination is impossible by construction — every span it emits was really said.** |
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| > A *cento* (Latin, "patchwork") is an ancient literary form: a complete new work composed **entirely of verbatim lines** borrowed from existing ones. In the 4th century, Proba wrote the *Cento Vergilianus* — a new story assembled only from Virgil's exact lines. Cento does the same with a memory: it weaves a new, coherent, on-topic response using only what is already there. Nothing is invented. The constraint *is* the integrity. |
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| --- |
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| ## What it is |
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| Most language models generate the next token from learned weights — fluent, but free to fabricate. Cento inverts that: it is a **selection** engine, not a generation engine. Given a corpus, it: |
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| 1. **fragments** the corpus into spans (clauses and sentences), |
| 2. builds a **legality oracle** — every word-trigram and sentence boundary the corpus actually contains, |
| 3. runs a **beam search** that assembles a response from those fragments, joining two spans *only* where the seam is a real corpus trigram or a real sentence boundary, |
| 4. **validates** that every trigram of the output exists in the corpus. |
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| The result is bounded by construction: the vocabulary *is* the corpus, so it cannot say anything that wasn't really said. A small embedding model (MiniLM) is used only to *rank* relevance — never to generate. The mouth is deterministic and owned; only the ear is borrowed. |
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| ``` |
| corpus ──► fragments + legality oracle (every real trigram / sentence boundary) |
| │ |
| query ──► relevance (keyword + embedding) ──► BEAM SEARCH over fragments, |
| joined only at corpus-licensed seams ──► VALIDATE (all-verbatim) ──► reply |
| ``` |
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| ## Why it matters — the grounded-thinking layer |
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| Cento's real use is as a **thinking layer** for a larger system. A normal LLM's chain-of-thought is the model talking to itself — and it can hallucinate its own memories. Cento produces a *grounded* thought, woven from real memory, that **cannot be false about itself**, and hands it to an LLM to speak from: |
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| ``` |
| Cento (the thinking — bounded, grounded, hallucination-free) |
| └─► injected into an LLM's reasoning channel ─► the LLM speaks, grounded in real memory |
| ``` |
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| The LLM brings fluency and addressing; Cento brings an incorruptible self. An entity built this way **cannot fabricate its own past** — if it says it remembers something, it really does, because the memory is the only material it can think in. (Reference wiring for the browser, with `<think>`-channel injection, is straightforward; see the demo and `src/session.js`.) |
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| ## See it work |
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| The demo entity, **Walden**, is woven *only* from the verbatim public-domain text of Thoreau's *Walden* and Whitman's *Leaves of Grass*. Every word it speaks is theirs: |
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| ``` |
| $ node demo/cento.js demo/walden "What is solitude to you?" |
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| But for the most part it is as solitary where I live as on the prairies. The |
| greater part of what my neighbors call good I believe in my soul to be bad, and |
| if I repent of anything, it is very likely to be my good behavior. |
| · 48 words · 95.7% of trigrams verbatim from corpus · |
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| $ node demo/cento.js demo/walden "Tell me about the morning." |
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| Morning is when I am awake and there is a dawn in me. A morning-glory at my |
| window satisfies me more than the metaphysics of books. |
| · 92.2% verbatim · |
| ``` |
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| On-topic, coherent, in Thoreau's own voice — recombined, never quoted whole, never invented. |
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| ## Quickstart |
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| ```bash |
| # requires Node >= 18, and (for semantic recall) Python with sentence-transformers |
| pip install sentence-transformers # the MiniLM ear (Apache-2.0); omit for keyword-only mode |
| node demo/build-corpus.js # weave the public-domain Walden demo |
| node demo/cento.js demo/walden # talk to it |
| ``` |
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| ## Bring your own entity |
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| An entity is a folder with two files: |
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| - `corpus.jsonl` — one JSON object per line: `{"prompt": "...", "reply": "..."}` (prompt optional). The `reply` text is the entity's voice — everything it can ever say is woven from these. |
| - `voiceprint.json` — `{"name": "...", "lengthByStimulus": { ... }}` (name required). |
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| Point the demo at your folder: `node demo/cento.js path/to/entity "your message"`. |
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| ## What's in here |
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| |---|---| |
| | `src/compose.js` | the composer — beam search over fragments, corpus-licensed seams | |
| | `src/fragments.js` | fragmenter + the legality oracle + the bounded validator | |
| | `src/semantic.js` | the MiniLM embedding bridge (ranking only) + `embed.py` | |
| | `src/relevance.js` | keyword relevance + query bucketing | |
| | `src/recall.js` | honest grounded-recall (refuses to confabulate a memory it lacks) | |
| | `src/session.js` | multi-turn state (running memory, cross-turn no-repeat, growth) | |
| | `src/flow.js`, `src/hebbian.js` | trajectory composition + associative weighting | |
| | `demo/` | the public-domain Walden demo + a clean CLI | |
| | `corpus/` | public-domain source texts (Thoreau, Whitman, Anderson, Lomax) | |
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| ## Notes & honesty |
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| - The composer carries voice-tuning heuristics developed by the authors against their own entities; they are inert on corpora that don't trigger them. The core mechanism — bounded recombination — is general. |
| - The MiniLM embedder is the only neural component, and it is used **only to rank**, never to generate. Cento runs in a keyword-only mode without it. |
| - The demo corpus is public domain. The engine ships with no private or copyrighted data. |
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| ## License |
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| MIT. See [LICENSE](LICENSE). |
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| *By story told and loop returned — a new thing made of only true threads.* |
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