# System Architecture

## Overview

Self-evolving AI trading agent for global stock markets via KIS (Korea Investment & Securities) API. The main loop in `src/main.py` orchestrates four components in a 60-second cycle per stock across multiple markets.

## Core Components

### 1. Broker (`src/broker/`)

**KISBroker** (`kis_api.py`) — Async KIS API client for domestic Korean market

- Automatic OAuth token refresh (valid for 24 hours)
- Leaky-bucket rate limiter (10 requests per second)
- POST body hash-key signing for order authentication
- Custom SSL context with disabled hostname verification for VTS (virtual trading) endpoint due to known certificate mismatch

**OverseasBroker** (`overseas.py`) — KIS overseas stock API wrapper

- Reuses KISBroker infrastructure (session, token, rate limiter) via composition
- Supports 9 global markets: US (NASDAQ/NYSE/AMEX), Japan, Hong Kong, China (Shanghai/Shenzhen), Vietnam (Hanoi/HCM)
- Different API endpoints for overseas price/balance/order operations

**Market Schedule** (`src/markets/schedule.py`) — Timezone-aware market management

- `MarketInfo` dataclass with timezone, trading hours, lunch breaks
- Automatic DST handling via `zoneinfo.ZoneInfo`
- `is_market_open()` checks weekends, trading hours, lunch breaks
- `get_open_markets()` returns currently active markets
- `get_next_market_open()` finds next market to open and when

### 2. Brain (`src/brain/gemini_client.py`)

**GeminiClient** — AI decision engine powered by Google Gemini

- Constructs structured prompts from market data
- Parses JSON responses into `TradeDecision` objects (`action`, `confidence`, `rationale`)
- Forces HOLD when confidence < threshold (default 80)
- Falls back to safe HOLD on any parse/API error
- Handles markdown-wrapped JSON, malformed responses, invalid actions

### 3. Risk Manager (`src/core/risk_manager.py`)

**RiskManager** — Safety circuit breaker and order validation

⚠️ **READ-ONLY by policy** (see [`docs/agents.md`](./agents.md))

- **Circuit Breaker**: Halts all trading via `SystemExit` when daily P&L drops below -3.0%
  - Threshold may only be made stricter, never relaxed
  - Calculated as `(total_eval - purchase_total) / purchase_total * 100`
- **Fat-Finger Protection**: Rejects orders exceeding 30% of available cash
  - Must always be enforced, cannot be disabled

### 4. Evolution (`src/evolution/optimizer.py`)

**StrategyOptimizer** — Self-improvement loop

- Analyzes high-confidence losing trades from SQLite
- Asks Gemini to generate new `BaseStrategy` subclasses
- Validates generated strategies by running full pytest suite
- Simulates PR creation for human review
- Only activates strategies that pass all tests

## Data Flow

```
┌─────────────────────────────────────────────────────────────┐
│ Main Loop (60s cycle per stock, per market)                │
└─────────────────────────────────────────────────────────────┘
                           │
                           ▼
        ┌──────────────────────────────────┐
        │ Market Schedule Check             │
        │ - Get open markets                │
        │ - Filter by enabled markets       │
        │ - Wait if all closed              │
        └──────────────────┬────────────────┘
                           │
                           ▼
        ┌──────────────────────────────────┐
        │ Broker: Fetch Market Data        │
        │ - Domestic: orderbook + balance  │
        │ - Overseas: price + balance      │
        └──────────────────┬────────────────┘
                           │
                           ▼
        ┌──────────────────────────────────┐
        │ Calculate P&L                     │
        │ pnl_pct = (eval - cost) / cost   │
        └──────────────────┬────────────────┘
                           │
                           ▼
        ┌──────────────────────────────────┐
        │ Brain: Get Decision               │
        │ - Build prompt with market data   │
        │ - Call Gemini API                 │
        │ - Parse JSON response             │
        │ - Return TradeDecision            │
        └──────────────────┬────────────────┘
                           │
                           ▼
        ┌──────────────────────────────────┐
        │ Risk Manager: Validate Order      │
        │ - Check circuit breaker           │
        │ - Check fat-finger limit          │
        │ - Raise if validation fails       │
        └──────────────────┬────────────────┘
                           │
                           ▼
        ┌──────────────────────────────────┐
        │ Broker: Execute Order             │
        │ - Domestic: send_order()          │
        │ - Overseas: send_overseas_order() │
        └──────────────────┬────────────────┘
                           │
                           ▼
        ┌──────────────────────────────────┐
        │ Database: Log Trade               │
        │ - SQLite (data/trades.db)         │
        │ - Track: action, confidence,      │
        │   rationale, market, exchange     │
        └───────────────────────────────────┘
```

## Database Schema

**SQLite** (`src/db.py`)

```sql
CREATE TABLE trades (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    timestamp TEXT NOT NULL,
    stock_code TEXT NOT NULL,
    action TEXT NOT NULL,          -- BUY | SELL | HOLD
    confidence INTEGER NOT NULL,   -- 0-100
    rationale TEXT,
    quantity INTEGER,
    price REAL,
    pnl REAL DEFAULT 0.0,
    market TEXT DEFAULT 'KR',       -- KR | US_NASDAQ | JP | etc.
    exchange_code TEXT DEFAULT 'KRX' -- KRX | NASD | NYSE | etc.
);
```

Auto-migration: Adds `market` and `exchange_code` columns if missing for backward compatibility.

## Configuration

**Pydantic Settings** (`src/config.py`)

Loaded from `.env` file:

```bash
# Required
KIS_APP_KEY=your_app_key
KIS_APP_SECRET=your_app_secret
KIS_ACCOUNT_NO=XXXXXXXX-XX
GEMINI_API_KEY=your_gemini_key

# Optional
MODE=paper                    # paper | live
DB_PATH=data/trades.db
CONFIDENCE_THRESHOLD=80
MAX_LOSS_PCT=3.0
MAX_ORDER_PCT=30.0
ENABLED_MARKETS=KR,US_NASDAQ  # Comma-separated market codes
```

Tests use in-memory SQLite (`DB_PATH=":memory:"`) and dummy credentials via `tests/conftest.py`.

## Error Handling

### Connection Errors (Broker API)
- Retry with exponential backoff (2^attempt seconds)
- Max 3 retries per stock
- After exhaustion, skip stock and continue with next

### API Quota Errors (Gemini)
- Return safe HOLD decision with confidence=0
- Log error but don't crash
- Agent continues trading on next cycle

### Circuit Breaker Tripped
- Immediately halt via `SystemExit`
- Log critical message
- Requires manual intervention to restart

### Market Closed
- Wait until next market opens
- Use `get_next_market_open()` to calculate wait time
- Sleep until market open time