Callbacks

React to streaming events for logging, UI updates, and integrations

Stream events let you react to agent activity – update UI, log activity, or integrate with other systems.

Quick Start

1. Create Stream Events

   use praisonai::{StreamEvent, StreamEventType};
   
   // Create a text delta event
   let event = StreamEvent::delta_text("Hello, ");
   
   // Create events for different stages
   let start = StreamEvent::request_start();
   let first = StreamEvent::first_token("The");
   let end = StreamEvent::stream_end();

2. Handle Events

   use praisonai::{StreamEvent, StreamEventType};
   
   fn handle_event(event: &StreamEvent) {
       match event.event_type {
           StreamEventType::RequestStart => println!("Starting..."),
           StreamEventType::FirstToken => println!("First token: {:?}", event.content),
           StreamEventType::DeltaText => print!("{}", event.content.as_deref().unwrap_or("")),
           StreamEventType::ToolCallEnd => println!("Tool complete"),
           StreamEventType::StreamEnd => println!("\nDone!"),
           StreamEventType::Error => eprintln!("Error: {:?}", event.error),
           _ => {}
       }
   }

3. Track Metrics

   use praisonai::StreamMetrics;
   
   let mut metrics = StreamMetrics::new();
   metrics.start();
   
   // ... process stream ...
   
   metrics.end();
   println!("Time to First Token: {:?}ms", metrics.time_to_first_token());
   println!("Total Tokens: {}", metrics.total_tokens());

StreamEventType

Events emitted during streaming.

pub enum StreamEventType {
    RequestStart,    // Before API call
    HeadersReceived, // HTTP headers arrived
    FirstToken,      // First content (TTFT marker)
    DeltaText,       // Text content chunk
    DeltaToolCall,   // Tool call in progress
    ToolCallEnd,     // Tool call complete
    LastToken,       // Final content chunk
    StreamEnd,       // Stream completed
    Error,           // Error occurred
}

StreamEvent

Structure for streaming events.

pub struct StreamEvent {
    pub event_type: StreamEventType,
    pub content: Option<String>,
    pub tool_call: Option<ToolCallData>,
    pub error: Option<String>,
    pub timestamp: DateTime<Utc>,
    // ... more fields
}

Factory Methods

Builder Methods

Best Practices

Related