Build an interaction carrying a single text message.
The content is the backend-neutral {role, content: [text part]} envelope,
so a plain text turn stays portable across a mid-conversation model switch.
content and system_instructions contain Chunk values. Building
those chunks uses the asynchronous serialization registry, equivalent to
a11.to_chunk in Python.
Build an interaction carrying a single text message.
The content is the backend-neutral
{role, content: [text part]}envelope, so a plain text turn stays portable across a mid-conversation model switch.contentandsystem_instructionscontain Chunk values. Building those chunks uses the asynchronous serialization registry, equivalent toa11.to_chunkin Python.