Events - PraisonAI

Events notify you when important things happen during agent execution. Use the StreamEvent system to track agent progress.

Quick Start

1

Create and Handle Events

use praisonai::{StreamEvent, StreamEventType};

fn handle_event(event: &StreamEvent) {
    match event.event_type {
        StreamEventType::RequestStart => println!("🚀 Starting..."),
        StreamEventType::FirstToken => println!("💬 First response"),
        StreamEventType::DeltaText => {
            if let Some(content) = &event.content {
                print!("{}", content);
            }
        }
        StreamEventType::DeltaToolCall => println!("🔧 Tool call"),
        StreamEventType::ToolCallEnd => println!("✅ Tool done"),
        StreamEventType::StreamEnd => println!("\n🏁 Complete"),
        StreamEventType::Error => {
            if let Some(err) = &event.error {
                eprintln!("❌ Error: {}", err);
            }
        }
        _ => {}
    }
}

2

Create Events

use praisonai::StreamEvent;

// Factory methods for common events
let start = StreamEvent::request_start();
let text = StreamEvent::delta_text("Hello, world!");
let end = StreamEvent::stream_end();
let error = StreamEvent::error_event("Something went wrong");

StreamEventType

Event	When
`RequestStart`	Before API call
`HeadersReceived`	HTTP headers arrive
`FirstToken`	First content received
`DeltaText`	Text content chunk
`DeltaToolCall`	Tool call in progress
`ToolCallEnd`	Tool finished executing
`LastToken`	Final content chunk
`StreamEnd`	Stream completed
`Error`	Error occurred

StreamEvent Structure

pub struct StreamEvent {
    pub event_type: StreamEventType,
    pub content: Option<String>,
    pub tool_call: Option<ToolCallData>,
    pub error: Option<String>,
    pub timestamp: DateTime<Utc>,
    pub is_reasoning: bool,
    pub agent_id: Option<String>,
    pub session_id: Option<String>,
}

Streaming

Enable streaming responses

Callbacks

React to stream events