StockSharp/StockSharp

StockSharp is a powerhouse in the retail and professional C# quantitative trading space. With a decade of development and nearly 10,000 stars, it has built a significant moat through its vast library of 70+ broker and exchange connectors. In trading, the 'integration surface' is the ultimate defensibility factor; maintaining connections to evolving APIs (FIX, WebSockets, REST) for diverse entities like Interactive Brokers, Binance, and various Russian/European exchanges is an immense task that discourages new entrants. It competes directly with QuantConnect (Lean) and MetaTrader, but remains a preferred choice for developers deeply embedded in the .NET ecosystem. Frontier labs pose almost zero risk here as the domain is highly regulated, specialized, and requires manual maintenance of legacy financial protocols that do not align with LLM scaling laws. The main risk is the broader industry shift toward Python (Pandas/VectorBT) for research, but for high-performance execution and specialized UI (WPF-based terminals), StockSharp remains a category leader with high switching costs.