Content that does not fit its type is refused instead of stored

Every node type declares the shape of its content: which fields exist and what each one holds. Until now nothing checked a write against that declaration. A write that put a whole object into a field declared as text — or whose field names matched nothing the type knows — was accepted, given a new version, and stored exactly as sent.

Nothing failed at that moment. The damage showed up later, and somewhere else: the record could no longer be read back as its own type, so every view of it came up empty. A page would show "No content yet" over a document that was still there in full, and the person who could have fixed the write in one retry was long gone.

Such a write is now refused at the point it is made, with a message in your language naming the field, what that field was declared to hold, and what was sent instead — so it can be corrected immediately.

The check is deliberately narrow, so that writes which were never the problem keep working. Content carrying an extra field alongside real ones still lands, as it always did: that is what an older or newer version of the same record looks like, and dropping such a field is already reported. Only two things are refused — a field whose value contradicts its declaration, and content in which not one field matches the type at all.