Type Alias ContentBlockStartEvent 

pub type ContentBlockStartEvent = MessageStreamEvent;

Aliased Type

pub enum ContentBlockStartEvent {
    MessageStart {
        message: Message,
    },
    MessageDelta {
        delta: MessageDelta,
        usage: MessageDeltaUsage,
    },
    MessageStop,
    ContentBlockStart {
        content_block: ContentBlock,
        index: usize,
    },
    ContentBlockDelta {
        delta: ContentBlockDelta,
        index: usize,
    },
    ContentBlockStop {
        index: usize,
    },
}

Variants

MessageStart

Initial event when a message starts being generated.

Contains the initial message structure with metadata but no content yet.

Fields

message: Message

The initial message structure

MessageDelta

Event when the message metadata is updated during generation.

Contains updates to stop reason, stop sequence, and usage information.

Fields

delta: MessageDelta

The delta containing updated fields

usage: MessageDeltaUsage

Current usage statistics

MessageStop

Final event when message generation is complete.

ContentBlockStart

Event when a new content block starts being generated.

This occurs when Claude begins generating a new piece of content (text, tool use, etc.).

Fields

content_block: ContentBlock

The content block being started

index: usize

Index of this content block in the message

ContentBlockDelta

Event containing incremental updates to a content block.

This is where you’ll receive the actual text being generated, tool input being parsed, etc.

Fields

delta: ContentBlockDelta

The incremental update

index: usize

Index of the content block being updated

ContentBlockStop

Event when a content block finishes generation.

Fields

index: usize

Index of the content block that finished