<p>Plant protein–polyphenol systems are increasingly explored for functional foods, but their performance cannot be predicted from ingredient identity or binding strength alone. Plant proteins differ in solubility, conformation, interfacial behavior, and processing sensitivity, while polyphenols differ in molecular size, hydroxylation, oxidation behavior, hydrophobicity, and capacity for multivalent association. This review examines plant protein–polyphenol interactions through a process-structure–function lens, with emphasis on food matrices rather than isolated model solutions. It covers non-covalent binding, oxidation-mediated conjugation, processing-induced assembly, storage stability, digestive disassembly, phenolic bioaccessibility, antioxidant interpretation, sensory consequences, and foodomics-supported mechanism validation. The main synthesis is that protein–polyphenol complexation can support emulsion protection, gel structuring, encapsulation, and phenolic retention under defined conditions, but the same interactions may also cause turbidity, precipitation, poor reconstitution, reduced proteolysis, limited phenolic release, astringency, or color instability. Stronger binding and higher chemical antioxidant capacity therefore should not be treated as direct evidence of improved nutritional or technological performance. Future studies should report formulation metadata more consistently, compare systems under matrix-relevant processing and storage conditions, connect molecular evidence with digestion and sensory endpoints, and use targeted foodomics to verify transformation products rather than infer mechanisms from indirect assays alone.</p> Graphical Abstract <p>Interaction trade-offs in plant protein–polyphenol functional food systems. Plant protein–polyphenol interactions are process-sensitive assemblies whose outcomes depend on protein source, polyphenol chemistry, and processing conditions. The same interactions may generate useful structures (soluble complexes, interfacial films, gels, encapsulates) or performance limitations (haze, sedimentation, excessive cross-linking, poor reconstitution). Key interpretive risks are highlighted: retained phenolics are not automatically bioaccessible, stronger binding does not guarantee better functionality, and chemical antioxidant capacity is not evidence of physiological relevance. Functional claims therefore require matrix-specific validation, digestion data and translational testing</p> <p></p>