source_too_large_for_model
What happened
Each turn sends the conversation and the source to the assistant, and the text has a size limit. A turn over it is refused with 413 before anything is reserved, so nothing is charged.
What to do
Start a new chat with a smaller or simpler source.
Example
json
{
"error": "This conversation is too long for a single turn \u2014 start a new chat.",
"code": "source_too_large_for_model"
}