downgradeUnsupportedImages function

List<Message> downgradeUnsupportedImages(List<Message> messages, Model model)

Replaces image blocks with explicit placeholder text when model has no image input, so nothing is dropped silently at request time.

Ported from the downgradeUnsupportedImages half of pi's transformMessages pre-pass (transform-messages.ts): user messages and tool results get distinct placeholders; the image bytes stay in the session transcript, only the request payload is rewritten. Each adapter runs this at the top of its message conversion.

Implementation

List<Message> downgradeUnsupportedImages(List<Message> messages, Model model) {
  if (model.input.contains('image')) {
    return messages;
  }
  var dropped = 0;
  final out = _replaceImages(
    messages,
    nonVisionUserImagePlaceholder,
    nonVisionToolImagePlaceholder,
    onImage: () => dropped++,
  );
  if (dropped > 0) textOnlyImageDropNotice?.call(dropped);
  return out;
}