Citation Sentinel

A source-grounded research assistant that employs cosine similarity scoring for LLM-generated query responses to provide a "groundedness" score. This is a metric in Retrieval-Augmented Generation (RAG) systems that quantifies how well an AI-generated answer is supported by retrieved context. It measures "faithfulness" to source documents, ensuring the answer is not hallucinated or pulled from the model's pre-training data.

Users upload source documents, or provide links to online sources including audio/video (i.e. links to youtube videos). Users may then ask questions and receive answers (with inline citations) verifiably grounded in the provided information sources.

Built with a React/Vite frontend and a Typescript/Node/Express backend, using Anthropic Claude for generation, OpenAI Whisper for video audio track transcription, Voyage AI for embeddings and response cosine similarity scoring (the "groundedness" score).

Query pipeline

Source Ingestion -> Parsing -> Chunking -> Embedding (using Voyage AI voyage-3 model) -> Storage (vector store) -> { user query submission } -> Evaluation of User Query -> Retrieval -> Ranking -> Response Generation (Using Anthopic's claude-opus-4-6 model) -> Response Groundedness Scoring (using Voyage AI rerank-r model)

Prerequisites

• Node.js (v18+)
• yt-dlp -- Required for YouTube video source support (brew install yt-dlp)

Getting Started

# clone and install
git clone <repo-url> && cd citation_sentinel
cd server && npm install && cd ..
cd client && npm install && cd ..

# configure
cp server/.env.example server/.env
# edit server/.env and add your ANTHROPIC_API_KEY, VOYAGE_API_KEY,
# and optionally OPENAI_API_KEY (only needed for audio source transcription via Whisper)

# run
make dev

Rationale

This app demonstrates the core source-grounded Q&A pattern with transparent retrieval, generation, and groundedness scoring (LLM response quality cosine scoring) -- all with swappable models and is fully open source.

Methodology

This is a RAG (Retrieval-Augmented Generation) and query-response source-groundedness assurance system allowing users to create a research knowledge corpus, including:

1. Documents — PDFs, DOCX files, plain text audio files.
2. Internet sources: via web URLs.
3. Audio sources: i.e. YouTube videos, audio from which is transcribed to text.

These are then parsed, split into ~2000-character overlapping chunks, and converted into vector embeddings using Voyage AI's voyage-3 model.

The embeddings are stored in an in-memory vector store.

When a user submits a query, the system enforces groundedness through a multi-layered strategy:

1. Retrieval constraint — The query is embedded (via Voyage AI voyage-3) and compared against stored chunk vectors using cosine similarity, returning the top 20 candidates.

2. Reranking for precision — Those 20 candidates are sent to Voyage AI's rerank-2 cross-encoder, which re-scores each query-chunk pair with deeper semantic analysis. Only the top 5 survive.

3. Prompt-level constraint — The top 5 chunks are passed to the "Primary LLM" (Claude opus-4-6) for natural language query response. The Primary LLM must cite sources using bracketed indices (e.g., [1], [2]) and admit when sources are insufficient.

4. Schema enforcement — The Primary LLM's response is constrained to a JSON schema requiring structured fields (answer, citedSourceIndices, followUpQuestions). Any cited source indices that do not correspond to real source groups are programmatically removed.

5. Post-generation groundedness scoring — The answer is split into individual sentences. Voyage AI voyage-3 embeds each sentence, and compares it (using cosine similarity) against the vectors of the cited chunks. The similarity is calibrated to a 0–1 scale and averaged, producing a single groundedness score that is surfaced to the user with a visual indicator (green/yellow/red).

Similarity Metrics for Semantic Understanding

Cosine similarity measures how closely two vectors (representing data like words, images, or preferences) are aligned in a multi-dimensional space by calculating the cosine of the angle between them.

Archetypical cosine scores range from -1 to 1.

1: Vectors point in the exact same direction (highly similar). 0: Vectors are at a 90-degree angle (orthogonal/unrelated). -1: Vectors point in opposite directions.

Cosine distance between high-dimensional text embeddings is compressed: unrelated notes sit close to orthogonal, so both the within-cluster and nearest-cluster distances land near 0.8. In this application, scores are normalized to a bounded range wherein unrelated query-response pair scores are nearly orthogonal.

Design

Two-package monorepo:

• server/ -- single Express backend with layered architecture (routes -> services -> stores). Routes orchestrate; services contain business logic; stores manage in-memory state.

• client/ -- React 19 SPA via Vite. Two-panel layout: sidebar for data sources, main area for LLM chat with explorable citations, groundedness badges (cosine similarity scoring of LLM responses), and follow-up question chips.

License

MIT. See LICENSE.

Author

@sjdev