Semantic Kernel (SK) provided a plugin-based architecture for connecting LLMs to application code, data, and services. Core concepts: Kernel (orchestrator + DI container), Plugins (collections of native C# functions or semantic string templates), Memory (vector storage connectors), Planners (auto-generate step-by-step execution plans from goals), and Process Framework for LangGraph-style stateful workflows. It integrated natively with Azure OpenAI and OpenAI and supported .NET best practices (dependency injection, async/await). In 2025 Microsoft merged SK with AutoGen into Microsoft Agent Framework (GA 1.0 April 2026); SK is now in maintenance mode (bug and security fixes only), and Microsoft Agent Framework is the recommended choice for new .NET and Python agentic development.
What it means in practice
Semantic Kernel is not just vocabulary; it is a design handle. Across agentic systems and .NET backend systems, this term connects implementation details with the bigger system decision being made. It is most useful when search quality, context selection, recall, latency, and answer grounding need to be measured together.
Why engineers care
- It gives teams a shared name for the behaviour, risk, or architecture choice being discussed.
- It helps separate the goal from the implementation detail, so you can compare alternatives instead of copying a tool pattern blindly.
- It creates a useful checklist for reviews: inputs, outputs, failure modes, ownership, cost, latency, and measurement.
Production watch-outs
Do not judge it by demo relevance alone. Track recall, precision, source freshness, chunk quality, failure cases, and the cost of retrieval plus generation.
Related context
Useful neighbouring concepts: Agent, Tool USE, RAG, Planning Loop.