State: TypeAlias = str | BaseMessage | Sequence[_StateValue] | MappingRoot state accepted by decision models.
State is a string, JSON object, or JSON array. LangChain BaseMessage objects and
message sequences can appear at the root or at any depth inside objects and arrays.
LangChain standard media blocks (for example {"type": "image", "base64": ..., "mime_type": ...}) may appear anywhere in the state. Each provider documents which
media it supports and how it sends state its API cannot accept natively.