# 밤사이 (Bamsai)

> 국내 주식시장이 닫힌 밤과 주말에도 하이퍼리퀴드(trade.xyz HIP-3)에서 거래되는 한국 주식 무기한 선물 가격을 업비트 원/USDC로 환산해, 다음 날 장 시작 가격의 상승 확률·예상 범위와 비용을 뺀 시세차익 기회를 보여주는 웹앱이에요.
> Bamsai shows Korean stocks' overnight and weekend prices from Hyperliquid perpetuals, converted to KRW with Upbit KRW-USDC, to forecast the next KRX opening price and the net spread after costs.

## What it answers
- "SK하이닉스 내일 장 시작하면 오를까?" — probability of an up open, expected opening price and the range it lands in 8 times out of 10 (80% band)
- "지금 해외 가격이랑 국내 가격 차이로 남는 돈이 있나?" — how far the premium sits from its usual level (median of the last 5 trading days' regular session), and what that leaves after fees, tax, FX and funding
- "이 예측 얼마나 맞았어?" — walk-forward backtest hit rate, band coverage and error per stock

## Assets
- SMSN 삼성전자 (005930), SKHX SK하이닉스 (000660), HYUNDAI 현대차 (005380): premium + next-open prediction
- SKHY SK하이닉스 ADR: compared with 0.1 common share, premium only
- KR200 코스피200, EWY MSCI Korea ETF, KORU 3x Korea ETF: Hyperliquid price only

## Method (short)
- Domestic market = KRX regular + Nextrade, 08:00–20:00 KST. Reference = last print at or before 20:00; target = 08:00–08:10 VWAP on the next trading day
- Re-open move = α + β × (Hyperliquid-implied move at 08:00 KST), β shrunk toward 1; σ split into weeknight vs weekend, plus closed-hours volatility × hours to open
- Main check: on nights with at least $1M traded on Hyperliquid while the domestic market is closed, did it re-open the way Hyperliquid moved? Since 2026-04-13 (moves within ±0.05% excluded): Samsung 88.2% (119 nights), SK hynix 85.4% (130); Hyundai undecided (7 such nights; 66.7% over all nights). Thin nights: 67.3% vs 86.3% pooled. Forecasts on thin nights carry `thin: true`
- Expected price (walk-forward): 80% band coverage 83–89%, mean error 1.1–1.3%p (plain Hyperliquid price as the guess: 1.2–1.4%p)
- Spread: net = |premium − usual premium| − costs; the usual premium drifts (Sep 2026 ≈ −0.5%, Oct +0.95%, Nov +0.5%), so a raw premium alone is not an opportunity
- Hyperliquid daily bars are re-cut to the domestic day (20:00 → 20:00 KST) so daily premiums compare the same moment

## API (no key for reads)
- [OpenAPI spec](/api/openapi.json)
- GET /api/v1/predict?asset=SKHX — next-open forecast
- GET /api/v1/arb — premium, usual premium (normalPremiumPct), deviation and net spread for all comparable assets
- GET /api/v1/convergence?asset=SMSN — per-open history: Hyperliquid move vs actual re-open move, follow, overnight Hyperliquid volume (nightUsd, nightKrw at that night's rate)
- GET /api/v1/series?asset=SKHX&interval=1h — overlaid candles (KRX + Hyperliquid in KRW), premium, funding, Hyperliquid listing time (listedAt)
- GET /api/v1/perps — Hyperliquid state for every asset
- MCP server: /api/mcp (Streamable HTTP)

## Pages
- [홈 (home)](/): next-open probability and spread opportunity for each stock
- [종목 상세 (stock detail)](/s/SKHX): chart | order book | order form in one screen; tomorrow's forecast and any spread opportunity are pinned on the chart at their prices; tabs for the forecast, prediction record (예측 기록) and investor flows
- [소개 (about)](/about): how every number is calculated, with a worked example and live hit rates
- [API](/developers): REST, OpenAPI and MCP usage

## Notes
- Reference information, not investment advice. Hyperliquid products are not covered by Korean investor protection.