langchain

d8996810 - feat(core): add XML format option for `get_buffer_string` (#34802)

feat(core): add XML format option for `get_buffer_string` (#34802) ## Summary Add XML format option for `get_buffer_string()` to provide unambiguous message serialization. This fixes role prefix ambiguity when message content contains strings like "Human:" or "AI:". Fixes #34786 ## Changes - Add `format="xml"` parameter with proper XML escaping using `quoteattr()` for attributes - Add explicit validation for format parameter (raises `ValueError` for invalid values) - Add comprehensive tests for XML format edge cases <img width="1952" height="706" alt="image" src="https://github.com/user-attachments/assets/1cd6f887-9365-43cf-a532-72d7addd8bad" /> <img width="2786" height="776" alt="image" src="https://github.com/user-attachments/assets/a07b0db0-519c-46d7-b34b-b404237d812b" /> --------- Co-authored-by: Mason Daugherty <github@mdrxy.com> Co-authored-by: Mason Daugherty <mason@langchain.dev>