Conversation Prefix Completion, FIM, and JSON Output Development Details
Jing Dai · 2025
This chapter focuses on advanced prompt engineering techniques in DeepSeek-V3, including prefix-based dialogue continuation, Fill-in-the-Middle (FIM) generation, and structured JSON output. It explains how to guide the model to generate coherent and context-aware continuations based on partial inputs, a critical feature for chatbots and story generation. This chapter also demonstrates the use of FIM for code and document editing tasks, enabling flexible content insertion. Furthermore, it outlines methods for constraining model outputs to valid JSON formats, supporting structured data extraction and API interaction. These techniques empower developers to build intelligent applications with higher controllability, enhanced context sensitivity, and structured output reliability.