Users may leave the page after uploading a file while processing continues. Design that lifecycle as part of modernization.
Define visible states
Separate received, validated, processing and failed. Identify who can view the file and its results. Avoid showing completion before required processing finishes.
Test interruptions
Check a lost connection, duplicate submission and a rejected file. The user needs a safe way to understand or resume work. Server-side validation remains necessary.
Prepare support
Give operators a record of the processing outcome without unnecessary sensitive content. Ask the partner to demonstrate recovery from a failed attempt. A smoother upload interface only helps if the application can account for what happened to the submitted file after the browser closes.
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