Why "copy ... from stdio" does not return immediately when reading invalid data?

Hello,

I am importing gigabytes of data into PostgreSQL, and I don't want to wait
10 minutes just to discover an error in the 10th line of my input file.

I tried the command "\copy ... from stdio" in psql and it looks like psql
has to read the entire input before returning a potential error, even if the
invalid value is in one of the first rows.

Is it a limitation of PostgreSQL protocol, of the library lipq, or of the
tool psql?

Is the copy protocol (aka PQputCopyData and PQputCopyEnd) designed to send
gigabytes of data with just one "copy ... from stdio" query, and is there a
way to be notified of a potential error before calling PQputCopyEnd? Or do I
have to send my data in small chunks (for example batch of 10000
rows), issue a PQputCopyEnd, check for errors, and continue with the next
chunk?

Thanks for your help and advice.

Regards,

Nicolas Grilly