Display Callbacks - PraisonAI

from praisonaiagents import Agent

agent = Agent(name="assistant", instructions="Be helpful.", output=True)
agent.start("Summarise this log file.")

Display callbacks let you react to agent events — tool calls, LLM turns, errors — without changing agent logic. The user runs the agent; display callbacks fire on tool calls, LLM turns, and errors for custom terminals or dashboards.

How It Works

Quick Start

from praisonaiagents import Agent, register_display_callback

def on_interaction(message=None, response=None, **kwargs):
    print(f"User: {message}")
    print(f"Agent: {response}")

register_display_callback("interaction", on_interaction)

agent = Agent(name="assistant", instructions="Be concise.")
agent.start("Say hello in one sentence.")

Log tool calls

from praisonaiagents import Agent, register_display_callback

def on_tool_call(tool_name=None, **kwargs):
    print(f"Tool: {tool_name}")

register_display_callback("tool_call", on_tool_call)

agent = Agent(
    name="researcher",
    instructions="Use tools when helpful.",
    tools=["web_search"],
)
agent.start("Latest Python release version?")

Async callback for dashboards

import asyncio
from praisonaiagents import Agent, register_display_callback

async def push_to_ui(message=None, response=None, **kwargs):
    await asyncio.sleep(0)  # replace with your WebSocket / HTTP call
    print({"message": message, "response": response})

register_display_callback("interaction", push_to_ui, is_async=True)

agent = Agent(name="assistant", instructions="Be helpful.")
agent.start("Summarise loop detection in one line.")

Callback Types

Type	When it fires
`interaction`	User message and agent response
`tool_call`	Before or during a tool invocation
`error`	Agent or tool error
`llm_start` / `llm_end`	LLM request lifecycle
`llm_content`	Streaming token chunks
`autonomy_iteration`	Autonomous loop iteration
`autonomy_doom_loop`	Doom loop detected in autonomy mode
`retry`	Retry after transient failure

Configuration Options

Option	Type	Default	Description
`display_type`	`str`	—	One of the supported callback types above
`callback_fn`	`callable`	—	Sync or async handler
`is_async`	`bool`	`False`	Store in the async registry when `True`

Callbacks receive keyword arguments matching the event (for example message, response, tool_name, agent_name). Extra kwargs are filtered to the function signature automatically.

Best Practices

Keep handlers lightweight

Display callbacks run on the hot path. Log or enqueue work — avoid heavy I/O in sync handlers.

Use async for network and UI

Set is_async=True when writing to WebSockets, Slack, or dashboards so the agent loop stays responsive.

Wrap custom logic in try/except

A failing callback should not crash the agent. Catch, log, and return.

Compose with hooks for fine control

Use display callbacks for output formatting; use hooks when you need to allow, block, or mutate tool calls.

Display System

TaskOutput, terminal rendering, and global registries

Callbacks

Broader callback patterns for agents and tasks

Per-Platform Display Policy

Output Styles

​How It Works

​Quick Start

​Callback Types

​Configuration Options

​Best Practices

​Related