The Anthropic provider had no Image variant in NativeContentOut, so
[IMAGE:data:image/jpeg;base64,...] markers produced by the multimodal
pipeline were sent to the API as plain text. The API counted every
base64 character as a token, reliably exceeding the 200k token limit
for any real image (a typical Telegram-compressed photo produced
~130k tokens of base64 text alone).
Fix:
- Add ImageSource struct and Image variant to NativeContentOut that
serializes to the Anthropic Messages API image content block format
- Add parse_inline_image() to decode data URI markers into Image blocks
- Add build_user_content_blocks() to split user message content into
Text and Image blocks using the existing parse_image_markers helper
- Update convert_messages() user arm to use build_user_content_blocks()
- Handle Image in the apply_cache_to_last_message no-op arm
Fixes#1626
d9c6dc4e04