File upload capability is one of the most underestimated constraints in professional AI workflows, because it determines not only what can be analyzed , but also how work must be structured , how often context must be rebuilt , and where hidden bottlenecks emerge  in real usage. The comparison between Gemini 3  and ChatGPT 5.2  reveals two very different philosophies in how file ingestion, format handling, and scale limits are designed and exposed to users. ····· File upload