If I enter a long content on a page, it will fail to save

If you enter the text of an entire book on a page, such as tens of thousands of words, an error will occur when saving

Failed to save entry: Form validation failed, please check your input

The issue names no file, test, or entry point. First reproduce the failure by saving a page containing tens of thousands of words, then trace the page-save validation path; done means the long content saves without the reported validation error.

Written by the indexing model from the issue text.