BetBasket

Trade prediction-market baskets like ETFs — one click, multiple markets.

Built at TreeHacks 2026.

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The Idea

Prediction markets (like Kalshi) let you bet on real-world outcomes — elections, Fed policy, AI milestones, sports. But placing individual bets across many markets is tedious. What if you could:

• Pick a theme — e.g., "AI stagnation in 2026"
• Build a basket — 5–10 related markets with one click
• Trade the whole basket — set a budget, preview cost, execute

Think of it as an ETF for prediction markets: diversify across a thesis instead of one-off contracts.

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What We Built

Three Ways to Build a Basket

Source	How it works
Pre-defined theme	Curated trend baskets: AI Stagnation, Trump Economic Agenda, Climate Goals, Cannabis Policy
Generate from trend	Describe a belief in plain English → GPT-4o-mini picks markets and directions
Search events	Browse top events by volume, search by keyword, use any event as a basket

UX Features

• For / Against toggle — Flip the whole basket from betting on the trend to betting against it
• Yes / No per leg — Simple labels instead of BUY_YES/BUY_NO/SELL_YES/SELL_NO
• Preview before execute — See estimated cost, contracts, and orderbook before placing orders
• Weighted legs — Adjust allocation per market (default: equal weight)

Tech Highlights

• SQLite events DB — Searchable index of 50k+ Kalshi events by volume
• Keyword expansion — "AI" → OpenAI, xAI, ChatGPT, Anthropic for smarter search
• Structured output — LLM returns JSON with market tickers, directions, weights (validated against candidate set)

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Tech Stack

Layer	Tech
Backend	FastAPI, Pydantic
Frontend	Streamlit
Database	SQLite (events index)
LLM	OpenAI GPT-4o-mini (structured output)
API	Kalshi demo (RSA-signed requests)

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Technical Challenges & How We Solved Them

1. Matching natural language to markets

Problem: User says "AI progress will stall" — how do we find relevant markets among 50k+ events?

Solution: Keyword extraction + expansion. Short terms like "ai" expand to ["OpenAI", "xAI", "ChatGPT", "Anthropic"] so we search the events DB for each. We batch-fetch full market data from Kalshi and pass ~80 candidates to the LLM with tickers, titles, and rules.

2. LLM hallucinating tickers

Problem: The model might invent tickers that don't exist or are closed.

Solution: Strict schema + validation. We use response_format with a JSON schema so the model returns only market_ticker, direction, weight. We filter each leg: if the ticker isn't in our candidate set, we drop it. No hallucinated contracts reach the basket.

3. Unified direction UX (For/Against vs Yes/No)

Problem: BUY_YES, BUY_NO, SELL_YES, SELL_NO are confusing. Users think in terms of "I bet on this" or "I bet against this."

Solution: Two-level abstraction. A global For / Against toggle flips all legs (BUY_YES ↔ BUY_NO, SELL_YES ↔ SELL_NO). Per-leg we display Yes / No — betting the outcome happens or doesn't. Internally we still send Kalshi’s 4-direction enum.

4. Events DB vs live API

Problem: Kalshi’s API returns events with nested markets, but searching by keyword isn’t supported. We need volume-ordered, searchable events.

Solution: One-time init script fetches all open events, parses market tickers, stores in SQLite with title, volume, markets_json. Search uses SQL LIKE on title/series/category. Generate-from-trend and Search share the same event pool.

5. Batch orders and pricing

Problem: Each leg needs a price (ask for buy, bid for sell). Orders are GTC resting orders.

Solution: basket_service fetches markets in batches, applies overrides (direction, weight, enabled), computes per-leg budget and contract counts, builds Kalshi batch order payload. Preview shows est. cost before execute.

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How to Run

Prerequisites

• Python 3.9+
• Kalshi demo account (no real money)
• Optional: OpenAI API key for "Generate from trend"

1. Clone & install

git clone <your-repo-url>
cd treehacks
python -m venv .venv
source .venv/bin/activate   # Windows: .venv\Scripts\activate
pip install -r backend/requirements.txt
pip install -r frontend/requirements.txt

2. Configure

cp backend/.env.example backend/.env

Edit backend/.env:

Variable	Required for	Where to get
KALSHI_API_KEY_ID	All	Kalshi demo → Account & security → API Keys
KALSHI_PRIVATE_KEY_PATH	All	Same page — download PEM, save as backend/kalshi_private.key
OPENAI_API_KEY	Generate from trend	platform.openai.com

3. Initialize events DB (required for search & generate)

cd backend
python scripts/init_events_db.py

Creates events.db with open events indexed by volume. Run once after clone; re-run if markets change.

4. Start the app

Terminal 1 — API

cd backend
uvicorn app.main:app --reload

Terminal 2 — UI

cd frontend
streamlit run streamlit_app.py

Open http://localhost:8501.

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Project Structure

treehacks/
├── backend/
│   ├── app/
│   │   ├── main.py           # FastAPI routes
│   │   ├── basket_service.py # Preview & execute
│   │   ├── llm_basket_service.py  # Generate from trend (LLM)
│   │   ├── events_db.py      # SQLite search
│   │   ├── kalshi_client.py  # RSA auth, markets, orders
│   │   └── models.py
│   ├── scripts/
│   │   ├── init_events_db.py # Populate events DB
│   │   └── build_themes_from_events.py
│   ├── themes.json           # Pre-defined trend baskets
│   └── requirements.txt
├── frontend/
│   ├── streamlit_app.py
│   └── requirements.txt
└── README.md

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License

MIT.

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Uses Kalshi demo — no real money. Trade at your own risk.