Blockchain technology is widely regarded as a transformative approach for strengthening food safety governance. However, inherent product attributes such as perishability and low standardization create incentives for production nodes to upload false information, substantially limiting the practical efficacy of blockchain in food supply chain management. Adopting a perspective that emphasizes the interaction between supply chain complexity and consensus mechanisms, this study develops a revenue model for production nodes to analyze the underlying profit formation mechanisms and applies evolutionary game theory to investigate their decision-making behavior concerning whether to autonomously improve product quality or upload high-quality information during the pre-chain stage. The results indicate that: (1) Supply chain complexity has a dual effect on node revenue, with the direction of impact determined by the net loss from blockchain adoption (defined as the difference between consensus cost and platform data effect value). Lower net loss enhances revenue, whereas higher net loss diminishes it. (2) Through its role in modulating risk exposure scale and interacting with the consensus mechanism, supply chain complexity exerts a threshold-dependent nonlinear influence on nodes' pre-chain autonomous behavior. The system achieves a stable equilibrium in which nodes voluntarily enhance product quality only when complexity surpasses a critical level and they cannot benefit from uploading false information. This research offers theoretical foundations and actionable pathways for redesigning food supply chain structures to address the challenge of pre-chain integrity.