Function message_image_summary 

pub fn message_image_summary(message: &ChatMessage) -> ImageMarkerSummary

Byte count of the text a message contributes and the number of images it contributes, following preparation. A tool-result carrier counts its declared IMAGE attachments and is never body-scanned, so marker syntax quoted in a carrier body is text, and a legacy carrier (nothing declared at the fixed position) contributes no images at all. A carrier’s text_bytes is its retained body length: the envelope’s content string for a native carrier, and the carrier text with its image attachment lines lifted (non-image lines retained) for a prompt carrier. That is what a current-turn dispatch delivers; a stale carrier is priced as its bytes by the estimator instead (see ImageMarkerDisposition::Stripped). Every other message falls back to the text-level image_marker_summary scan of its content.