A provisional application can be filed and up to a year later converted to a full patent application with the proviso that no claims are made not supported by the disclosures in the provisional application.
There are risks to this approach, but if for whatever reason a full patent cannot be filed, e.g. before a conference disclosing information, then a provisional application is a way to allow such public disclosures and secure a priority date potentially before anyone else files similar disclosures.
Can be a justified approach, which I have used in the past myself.
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