Veritas — Real-Time Video Fact Checker

A Chrome extension that fact-checks YouTube videos in real time. Closed captions are streamed to a FastAPI backend where Google Gemma extracts check-worthy claims; a Fetch.ai uAgent gathers evidence from Wikipedia and Google Fact Check Tools, consults a semantic vector cache, and renders verdicts with citations. An integrated chat lets you ask questions about the video as you watch.

Features

• Live fact-checking — Claims are extracted from captions automatically and checked against real sources.
• Verdict cards — Color-coded results (true, false, misleading, needs_context) with confidence scores, rationale, and source links.
• Ask Veritas — Chat with an AI assistant that has context from the video transcript.
• Semantic cache — SQLite + Gemini embeddings so paraphrased claims are answered instantly.
• Video-aware — Scrapes video title, channel, description, and publish date to help the LLM resolve pronouns and understand context.
• Expandable UI — Draggable, collapsible panel with a resizable split between fact-check results and chat.

Quick Start

1. Backend

cd backend
cp ../.env.example .env          # fill in API keys
./scripts/dev-backend.sh

Health check: curl http://localhost:8787/health

2. Fact-check uAgent

In a separate terminal:

./scripts/dev-agent.sh

The first run prints an agent1q... address. Set it in backend/.env:

FACTCHECK_AGENT_SEED=any-stable-phrase
FACTCHECK_AGENT_ADDRESS=agent1q...

Then restart the agent. Smoke test:

backend/.venv/bin/python scripts/test_factcheck_agent.py "The Eiffel Tower is 330 meters tall"

3. Chrome Extension

1. Open chrome://extensions → enable Developer mode.
2. Load unpacked → select the extension/ folder.
3. Open a YouTube video. The Veritas panel appears.
4. Click Start.

Configuration

Set in backend/.env (see .env.example):

Variable	Purpose
GEMMA_API_KEY	Google API key for Gemma (claims + verdicts) and Gemini (embeddings)
GOOGLE_FACTCHECK_API_KEY	Google Fact Check Tools API (optional, falls back to GEMMA_API_KEY)
FACTCHECK_AGENT_SEED	Stable seed phrase for deterministic agent address
FACTCHECK_AGENT_ADDRESS	The agent1q... address printed on first agent run
AGENTVERSE_MAILBOX_KEY	JWT from agentverse.ai for auto-registration (optional)
HOST, PORT	Backend bind address (default 0.0.0.0:8787)

Repo Layout

veritas/
├── backend/                      # FastAPI service (Python)
│   └── app/
│       ├── main.py
│       ├── config.py             # pydantic-settings
│       ├── ws/                   # WebSocket endpoints
│       ├── pipeline/             # orchestrator, claim extraction, verdict prompts, chat
│       ├── agents/               # uAgent + client (Fetch.ai)
│       ├── rag/                  # SQLite vector cache
│       └── adapters/             # Gemma LLM, Gemini embeddings, Wikipedia, Google Fact Check
├── extension/                    # Chrome MV3 extension (vanilla JS, no build step)
│   ├── manifest.json
│   ├── background/               # service worker — WS management
│   ├── content/                  # YouTube caption observer + overlay UI + chat
│   ├── overlay/                  # CSS theme
│   ├── popup/                    # toolbar popup
│   └── lib/                      # config, message types
├── scripts/                      # dev scripts, smoke tests
├── PLAN.md                       # original design doc
└── DEVPOST.md                    # hackathon submission write-up

Built With

Python, JavaScript, FastAPI, Google Gemma, Google Gemini, Fetch.ai uAgents, Agentverse, Chrome Extensions (MV3), SQLite, Wikipedia API, Google Fact Check Tools API, WebSockets, Pydantic