arXiv:2610.29758v1 Announce Type: new Abstract: The use of AI-based tools in software development is rapidly changing how software is produced, enabling large volumes of code to be generated with limited human implementation effort. However, this raises fundamental challenges for ensuring that generated artifacts are aligned with developer intent and have been appropriately validated. In this work, we propose the use of structured argumentation in driving AI-assisted software development. Inspired by techniques from assurance engineering for safety-critical systems, we define a language of justification rationales that explicitly relate informal natural language prompts, formal specifications, assumptions about developer intentions, and program analysis evidence in a structured and verifiable format. We then describe AssureCode, a tool-supported methodology for creating such rationales as part of agentic code generation. We provide an empirical analysis of our implementation where we investigate its capacity to contribute towards justified assurance of correctness for AI-generated code.