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Architecture

Showcase

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Beyond Traditional RAG

Most RAG systems follow a simple pipeline: split text → embed → retrieve → generate. NexusRAG goes further at every stage:

Aspect	Traditional RAG	NexusRAG
Document Parsing	Plain text extraction, structure lost	Docling: preserves headings, page boundaries, formulas, layout
Images & Tables	Ignored entirely	Extracted, captioned by vision LLM, embedded as searchable vectors
Chunking	Fixed-size splits, breaks mid-sentence	Hybrid semantic + structural chunking (respects headings, tables)
Embeddings	Single model for everything	Dual-model: BAAI/bge-m3 (1024d, search) + KG embedding (Gemini 3072d / Ollama / sentence-transformers)
Retrieval	Vector similarity only	3-way parallel: Vector over-fetch + KG entity lookup + Cross-encoder rerank
Knowledge	No entity awareness	LightRAG graph: entity extraction, relationship mapping, multi-hop traversal
Context	Raw chunks dumped to LLM	Structured assembly: KG insights → cited chunks → related images/tables
Citations	None or manual	Auto-generated 4-char IDs with page number and heading path
Page awareness	Lost after chunking	Preserved end-to-end: chunk → citation → document viewer navigation

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Features

Deep Document Parsing (Docling)

NexusRAG uses Docling for structural document understanding — not just text extraction:

• Structural preservation — Heading hierarchy (H1 > H2 > H3), page boundaries, paragraph grouping
• Formula enrichment — LaTeX math notation preserved during conversion
• Multi-format — PDF, DOCX, PPTX, HTML, TXT with consistent output
• Hybrid chunking — HybridChunker(max_tokens=512, merge_peers=True) respects semantic AND structural boundaries — never splits mid-heading or mid-table
• Page-aware metadata — Every chunk carries its page number, heading path, and references to images/tables on the same page

Hybrid Retrieval Pipeline

Stage	Technology	Details
Vector Embedding	BAAI/bge-m3	1024-dim multilingual bi-encoder (100+ languages)
KG Embedding	Gemini / Ollama / sentence-transformers	Configurable: Gemini (3072d), Ollama, or local sentence-transformers (e.g. bge-m3 1024d)
Vector Search	ChromaDB	Cosine similarity, over-fetch top-20 candidates
Knowledge Graph	LightRAG	Entity/relationship extraction, keyword-to-entity matching
Reranking	BAAI/bge-reranker-v2-m3	Cross-encoder joint scoring — encodes (query, chunk) pairs together
Generation	Gemini / Ollama	Agentic streaming chat with function calling

Why two embedding models? Vector search needs speed (local bge-m3, 1024-dim). Knowledge graph extraction needs semantic richness for entity recognition — choose Gemini Embedding (3072-dim, cloud), Ollama, or sentence-transformers (fully local, no API needed). Each model is optimized for its role.

Retrieval flow:

1. Parallel retrieval — Vector over-fetch (top-20) + KG entity lookup run simultaneously
2. Cross-encoder reranking — All 20 candidates scored jointly with the query through a transformer (far more precise than cosine similarity alone)
3. Filtering — Keep top-8 above relevance threshold (0.15), with fallback to top-3 if all below
4. Media discovery — Find images and tables on the same pages as retrieved chunks

Visual Document Intelligence

Images and tables are embedded into chunk vectors — not stored separately. When Docling extracts an image on page 5, its LLM-generated caption is appended to the text chunks on that page before embedding. This means searching for "revenue chart" finds chunks that contain the chart description, without needing a separate image search index.

Image Pipeline

1. Docling extracts images from PDF/DOCX/PPTX (up to 50 per document, 2x resolution)
2. Vision LLM (Gemini Vision or Ollama multimodal) generates captions: specific numbers, labels, trends
3. Captions appended to page chunks: [Image on page 5]: Graph showing 12% revenue growth YoY
4. Chunk is embedded → image becomes vector-searchable through its description
5. During retrieval, images on matched pages are surfaced as [IMG-p4f2] references

Table Pipeline

1. Docling exports tables as structured Markdown (preserving rows, columns, dimensions)
2. Text LLM summarizes each table: purpose, key columns, notable values (max 500 chars)
3. Summaries appended to page chunks: [Table on page 5 (3x4)]: Annual sales by region
4. Table summaries injected back into document Markdown as blockquotes for the document viewer

Citation System

Every answer is grounded in source documents with 4-character citation IDs (e.g., [a3z1]):

• Inline citations — Clickable badges embedded directly in the answer text
• Source cards — Each citation shows filename, page number, heading path, and relevance score
• Cross-navigation — Click a citation to jump to the exact section in the document viewer
• Image references — Visual content cited separately as [IMG-p4f2] with page tracking
• Strict grounding — The LLM is instructed to only cite sources that directly support claims, max 3 per sentence

Knowledge Graph Visualization

Interactive force-directed graph built from extracted entities and relationships:

• Entity types — Person, Organization, Product, Location, Event, Technology, Financial Metric, Date, Regulation (configurable)
• Force simulation — Repulsion + spring forces + center gravity with real-time physics
• Pan & zoom — Mouse drag, scroll wheel (0.3x-3x), keyboard reset
• Node interaction — Click to select, hover to highlight connected edges, drag to reposition
• Entity scaling — Node radius proportional to connectivity (degree)
• Query modes — Naive, Local (multi-hop), Global (summary), Hybrid (default)
• No extra services — LightRAG uses file-based storage (NetworkX + NanoVectorDB), zero Docker overhead

Multi-Provider LLM

Switch between cloud and local models with a single environment variable:

Gemini (Cloud)

Model	Best For	Thinking
gemini-2.5-flash	General chat, fast responses	Budget-based (auto)
gemini-3.1-flash-lite	High throughput, cost-effective Recommended default	Level-based: minimal / low / medium / high

Extended thinking is automatically configured — Gemini 2.5 uses thinking_budget_tokens, Gemini 3.x uses thinking_level.

Ollama (Local / Self-hosted)

Model	Parameters	Recommendation
qwen3.5:9b	9B	Good multilingual support, solid tool calling Recommended default
qwen3.5:4b	4B	Lightweight, works on 8GB RAM. May miss some tool calls
gemma3:12b	12B	Best balance of quality and speed.

Tip: For Knowledge Graph extraction, larger models (12B+) produce significantly better entity/relationship quality. Smaller models (4B) may extract zero entities on complex documents.

Provider switching — Comment/uncomment blocks in .env:

# Cloud (Gemini)
LLM_PROVIDER=gemini
GOOGLE_AI_API_KEY=your-key

# Local (Ollama) — uncomment to switch
# LLM_PROVIDER=ollama
# OLLAMA_MODEL=gemma3:12b

KG Embedding Providers

The Knowledge Graph embedding model is configured separately from the chat LLM:

Provider	Config	API Required	Dimension
Gemini (default)	KG_EMBEDDING_PROVIDER=gemini	Google AI API key	3072
Ollama	KG_EMBEDDING_PROVIDER=ollama	Ollama server	Varies
sentence-transformers	KG_EMBEDDING_PROVIDER=sentence_transformers	None (fully local)	Model-dependent (e.g. 1024 for bge-m3)

# Fully local KG embeddings — no API or external service needed
KG_EMBEDDING_PROVIDER=sentence_transformers
KG_EMBEDDING_MODEL=BAAI/bge-m3
KG_EMBEDDING_DIMENSION=1024

Tip: sentence_transformers reuses the same BAAI/bge-m3 model already downloaded for vector search — zero extra disk space, zero API costs, fully offline.

Agentic Streaming Chat

The chat system uses a semi-agentic architecture with real-time SSE streaming:

• Agent steps — Visual timeline: Analyzing → Retrieving → Generating → Done (with live timers)
• Extended thinking — Gemini/Ollama reasoning displayed in a collapsible panel
• Function calling — Native (Gemini) or prompt-based (Ollama) search_documents tool
• Force-search mode — Pre-retrieval before LLM generation for guaranteed grounded answers
• Heartbeat — 15s SSE keepalive prevents TCP timeout on slow responses
• Fallback — If Ollama produces empty output, auto-triggers search + retry
• Chat history — Persistent per workspace with message ratings (thumbs up/down)

UI / UX

Theme & Layout

• Dark / Light mode with smooth transition, persisted preference
• Collapsible sidebar with workspace navigation (icon-only mode at narrow width)
• Responsive grid layouts — mobile to desktop

Chat Interface

• Streaming token rendering with memoized paragraph blocks (only active block re-renders)
• Inline citation badges with hover tooltips (source file, page, heading path, relevance %)
• Agent step timeline with spinner animations and elapsed timers
• Thinking panel — scrollable, auto-follow, collapsible after completion
• Code blocks with syntax highlighting (Python, JS, SQL, etc.) and one-click copy

Document Management

• Drag-and-drop upload (PDF, DOCX, PPTX, TXT, MD — up to 50MB)
• Status badges with shimmer animation during processing
• Per-document chips: pages, chunks, images, tables, file size, processing time

Search

• 4 query modes: Hybrid, Vector, Local KG, Global KG
• Adjustable result count (1-20) with slider + direct input
• Document scope filtering (multi-select)
• Relevance score bars with color coding (green / amber / red)

Analytics Dashboard

• Stat cards: documents, indexed, chunks, images, entities, relationships
• Entity type distribution bar with animated widths
• Top entities ranked by connectivity
• Per-document chunk breakdown chart

Micro-interactions

• Framer Motion animations throughout (staggered entrances, layout transitions)
• Loading skeletons, toast notifications, empty state illustrations
• Keyboard shortcuts: / to focus search, Enter to send, Escape to cancel

Workspace System

• Multiple isolated knowledge bases, each with its own documents, ChromaDB collection, and KG
• Custom system prompt per workspace (override default Q&A behavior)
• Independent chat history with message persistence and ratings

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Evaluation

NexusRAG was evaluated using two complementary methods: 16 hand-crafted tests (rule-based metrics) and 30 RAGAS synthetic tests (LLM-as-judge). Test corpus: TechVina Annual Report 2025 (Vietnamese, 26 chunks) + DeepSeek-V3.2 Technical Paper (English, 57 chunks).

Phase 1 — Hand-crafted Tests (Rule-based)

16 tests across 6 categories using 8 rule-based metrics (keyword coverage, refusal accuracy, citation format, language match, etc.) — no LLM judge involved.

Category	Pass Rate	Avg Score
Fact Extraction (VI + EN)	5/5	0.93
Table Data	2/3	0.83
Cross-Document Reasoning	2/2	0.89
Anti-Hallucination	3/3	1.00
Multi-turn History	2/2	0.87
Citation Accuracy	1/1	0.85
Overall	15/16	0.89 — EXCELLENT

Phase 3 — RAGAS Synthetic Tests (LLM Judge)

30 auto-generated Q&A pairs evaluated by Gemini 2.0 Flash as RAGAS judge. Same questions tested on both models:

Metric	gemma3:12b (local)	gemini-2.5-flash (cloud)	Winner
Overall score	0.832	0.846	Gemini
Pass rate	25/30 (83%)	26/30 (87%)	Gemini
Faithfulness	0.749	0.812	Gemini (+0.063)
Factual correctness	0.773	0.749	gemma3 (+0.024)
Context recall	0.833	0.833	Tie
Table extraction	0.697	0.905	Gemini (+0.208)
Avg latency	3076ms	3283ms	gemma3 (-207ms)

Strengths & Known Limitations

Aspect	Status	Detail
Anti-hallucination	:green_circle: Strong	Perfect refusal on out-of-scope questions
Citation format	:green_circle: Strong	100% correct format across all tests
Cross-doc reasoning	:green_circle: Strong	Successfully synthesizes across multiple sources
Table parsing	:yellow_circle: Model-dependent	gemma3 fails complex tables; Gemini handles well
Language consistency	:yellow_circle: Model-dependent	gemma3 occasionally responds in wrong language
Retrieval coverage	:red_circle: Weak	5 cases with context_recall = 0 (specific facts missed by retrieval)
Faithfulness	:red_circle: Weak	4 FAIL cases — LLM adds unsupported details when elaborating

Full evaluation methodology and per-sample results: rag_evaluation_report.md

Planned Evaluation

Upcoming model benchmarks on the same 30 RAGAS test suite:

Model	Type	Status
gemma3:12b	Local (Ollama)	:white_check_mark: Done
gemini-2.5-flash	Cloud (Google AI)	:white_check_mark: Done
qwen3.5:4b	Local (Ollama)	:hourglass: Planned
qwen3.5:9b	Local (Ollama)	:hourglass: Planned
gemini-3.1-flash-lite	Cloud (Google AI)	:hourglass: Planned

Goal: compare cost-efficiency (local 4B/9B) vs cloud quality across faithfulness, table extraction, and multilingual consistency.

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Tech Stack

Backend

Technology	Purpose
FastAPI	Async web framework with SSE streaming
SQLAlchemy 2.0	Async ORM with PostgreSQL (asyncpg)
ChromaDB	Vector store — cosine similarity, per-workspace collections
LightRAG	Knowledge graph — entity extraction, multi-hop queries
Docling	Document parsing — PDF, DOCX, PPTX, HTML with structural extraction
sentence-transformers	BAAI/bge-m3 embeddings + BAAI/bge-reranker-v2-m3 reranking
google-genai	Gemini API — chat, vision, function calling, extended thinking
ollama	Local LLM — tool calling via prompt tags, multimodal support

Frontend

Technology	Purpose
React 19 + TypeScript 5.9	UI framework with strict typing
Vite 7	Dev server and production bundler
TailwindCSS 4	Utility-first styling with dark / light theme
Zustand 5	Lightweight state management
React Query 5	Async data fetching, caching, and mutations
Framer Motion 12	Layout animations, transitions, staggered entrances
react-markdown + KaTeX	Rich markdown with LaTeX math rendering
Lucide React	Icon library

Infrastructure

Technology	Purpose
PostgreSQL 15	Document metadata, chat history, workspace config
ChromaDB	Vector embeddings (HTTP client, containerized)
LightRAG	File-based KG (NetworkX + NanoVectorDB — no extra services)
Docker Compose	Full-stack deployment (4 containers)
nginx	Production frontend serving + API/SSE reverse proxy

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Quick Start

Option A: Docker (Full Stack)

git clone https://github.com/LeDat98/NexusRAG.git
cd NexusRAG
cp .env.example .env
# Edit .env — set GOOGLE_AI_API_KEY (or switch to Ollama)
docker compose up -d

First build takes ~5-10 minutes (downloads ML models ~2.5GB). Open http://localhost:5174

Option B: Local Development

git clone https://github.com/LeDat98/NexusRAG.git
cd NexusRAG
./setup.sh

The script checks prerequisites, creates venv, installs deps, starts PostgreSQL + ChromaDB, and optionally downloads ML models.

# Terminal 1 — Backend (port 8080)
./run_bk.sh

# Terminal 2 — Frontend (port 5174)
./run_fe.sh

Open http://localhost:5174

System Requirements

Resource	Minimum	Recommended
RAM	4 GB	8 GB+
Disk	5 GB	10 GB+
Python	3.10+	3.11+
Node.js	18+	22 LTS
Docker	20+	Latest

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Configuration

Copy .env.example and configure:

cp .env.example .env

Required

Variable	Description
GOOGLE_AI_API_KEY	Google AI API key (required for Gemini provider)

LLM

Variable	Default	Description
LLM_PROVIDER	gemini	gemini or ollama
LLM_MODEL_FAST	gemini-2.5-flash	Model for chat and KG extraction
LLM_THINKING_LEVEL	medium	Gemini 3.x thinking: minimal / low / medium / high
LLM_MAX_OUTPUT_TOKENS	8192	Max output tokens (includes thinking)
OLLAMA_HOST	http://localhost:11434	Ollama server URL
OLLAMA_MODEL	gemma3:12b	Ollama model name

KG Embedding

Variable	Default	Description
KG_EMBEDDING_PROVIDER	gemini	gemini, ollama, or sentence_transformers
KG_EMBEDDING_MODEL	text-embedding-004	Model name (provider-specific)
KG_EMBEDDING_DIMENSION	3072	Embedding dimension (must match model)

RAG Pipeline

Variable	Default	Description
NEXUSRAG_EMBEDDING_MODEL	BAAI/bge-m3	Embedding model (1024-dim)
NEXUSRAG_RERANKER_MODEL	BAAI/bge-reranker-v2-m3	Cross-encoder reranker
NEXUSRAG_VECTOR_PREFETCH	20	Candidates before reranking
NEXUSRAG_RERANKER_TOP_K	8	Final results after reranking
NEXUSRAG_ENABLE_KG	true	Enable knowledge graph extraction
NEXUSRAG_ENABLE_IMAGE_EXTRACTION	true	Extract images from documents
NEXUSRAG_ENABLE_IMAGE_CAPTIONING	true	LLM-caption images for search
NEXUSRAG_KG_LANGUAGE	Vietnamese	KG extraction language

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Roadmap

• Multimodal Retrieval — Integrate Gemini Embedding 2 (multimodal) for audio and video input retrieval — ask questions about podcasts, lectures, or video content directly
• Marker PDF Parser — Add Marker as an alternative document parser with superior math/formula extraction (LaTeX via Surya), lighter GPU footprint (~2-4GB VRAM vs Docling's ~18-20GB), and switchable via NEXUSRAG_DOCUMENT_PARSER=marker env config

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API

All endpoints prefixed with /api/v1. Interactive docs at http://localhost:8080/docs

Workspaces

Method	Endpoint	Description
GET	/workspaces	List all workspaces
POST	/workspaces	Create workspace
PUT	/workspaces/{id}	Update workspace
DELETE	/workspaces/{id}	Delete workspace + all data

Documents

Method	Endpoint	Description
POST	/documents/upload/{workspace_id}	Upload file
GET	/documents/{id}/markdown	Get parsed content
GET	/documents/{id}/images	List extracted images
DELETE	/documents/{id}	Delete document

RAG — Search, Chat, Analytics

Method	Endpoint	Description
POST	/rag/query/{workspace_id}	Hybrid search
POST	/rag/chat/{workspace_id}/stream	Agentic streaming chat (SSE)
GET	/rag/chat/{workspace_id}/history	Chat history
POST	/rag/process/{document_id}	Process document
GET	/rag/graph/{workspace_id}	Knowledge graph data
GET	/rag/analytics/{workspace_id}	Full analytics

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Star History

Star History

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