Module message 

Conversation message model: Message, its block enums, and the SystemPrompt / CacheControl support types.

Structs

SystemBlock

One entry inside a SystemPrompt::Blocks sequence.

ToolResultContent

Body of a tool reply sent back to the model in a UserBlock::ToolResult.

Enums

AssistantBlock

One block inside a Message::Assistant turn.

CacheControl

Cache breakpoint placed on a content block, system prompt block, or tool definition. Providers that support prompt caching (Anthropic today) read these to decide which prefix is cacheable and at what TTL; providers without explicit caching ignore the field. The presence of cache_control only declares intent — the actual cache hit/miss is reported via crate::Usage::cached_input_tokens and the cache-creation counters.

Message

One turn in the conversation history exchanged with a provider.

Source

Source of an image or document content block.

SystemPrompt

System prompt passed to the provider. Plain(String) matches the pre-caching API and is what From<String> / From<&str> produce — callers that don’t care about prompt caching keep using strings. Blocks(...) opts in to per-block cache breakpoints (Anthropic emits the system field as an array; other providers concatenate the block texts).

ToolResultBlock

One block inside a ToolResultContent::blocks list.

UserBlock

One block inside a Message::User turn.