BALI: Branch-Aware Loop Invariant Inference with Large Language Models

Abstract: Loop invariants are fundamental for reasoning about the correctness of iterative algorithms. However, deriving suitable invariants remains a challenging and often manual task, particularly for complex programs. In this paper, we introduce BALI, a branch-aware framework that integrates LLMs to enhance the inference and verification of loop invariants. Our approach combines automated reasoning with branch-aware static program analysis to improve both precision and scalability. Specifically, unlike prior LLM-only guess-and-check methods, BALI first verifies branch-sequence-level (path-level) clauses with SMT and then composes them into program-level invariants. We outline its key components, present preliminary results, and discuss future directions toward fully automated invariant discovery.