TqSdk (天勤量化) is a comprehensive Python SDK for quantitative trading in Chinese futures, options, and stock markets. It provides real-time market data via WebSocket, multi-broker account management (CTP, simulation, backtest), order execution, position management, and a full backtesting engine with replay capabilities. The architecture follows a client-server diff protocol: the SDK maintains an in-memory snapshot of business data (quotes, orders, positions) and processes incremental updates delivered via an async event loop. Users write strategies as Python scripts using `TqApi`, `wait_update()`, and helper classes like `TargetPosTask`. The SDK includes a rich set of demo strategies, technical indicators (60+), options pricing (Black-Scholes Greeks), risk management rules, scenario trials, and a web GUI for visualization. It also provides AI skill packs for integration with coding assistants. While primarily an application library, it contains strong data engineering components for time-series handling and backtesting.