A deep dive into the architecture and implementation of JetBrains AI – the backbone of AI Assistant in JetBrains IDEs, Grazie, and other JetBrains products. The JetBrains AI platform covers a broad range of functionality, from coding to writing assistance. We will discuss both JetBrains’s own models and the caveats of integration with some well-known LLM providers. We will also shed light on inference techniques used in JetBrains AI products.