---
title: "Lifecycle Hooks"
description: "Customize agent behavior with lifecycle hooks"
icon: "Wrench"
mode: "wide"
---

OpenBrowser provides lifecycle hooks that allow you to execute custom code at specific points during the agent's execution.
Hook functions can be used to read and modify agent state while running, implement custom logic, change configuration, integrate the Agent with external applications.

## Available Hooks

Currently, OpenBrowser provides the following hooks:

| Hook            | Description                                  | When it's called                                                                                  |
| --------------- | -------------------------------------------- | ------------------------------------------------------------------------------------------------- |
| `on_step_start` | Executed at the beginning of each agent step | Before the agent processes the current state and decides on the next action                       |
| `on_step_end`   | Executed at the end of each agent step       | After the agent has executed all the actions for the current step, before it starts the next step |

```python
await agent.run(on_step_start=..., on_step_end=...)
```

Each hook should be an `async` callable function that accepts the `agent` instance as its only parameter.

### Basic Example

```python
import asyncio
from pathlib import Path

from openbrowser import Agent, ChatOpenAI
from openbrowser.browser.events import ScreenshotEvent


async def my_step_hook(agent: Agent):
	# inside a hook you can access all the state and methods under the Agent object:
	#   agent.settings, agent.state, agent.task
	#   agent.tools, agent.llm, agent.browser_session
	#   agent.pause(), agent.resume(), agent.add_new_task(...), etc.

	# You also have direct access to the browser state
	state = await agent.browser_session.get_browser_state_summary()

	current_url = state.url
	visit_log = agent.history.urls()
	previous_url = visit_log[-2] if len(visit_log) >= 2 else None
	print(f'Agent was last on URL: {previous_url} and is now on {current_url}')
	cdp_session = await agent.browser_session.get_or_create_cdp_session()

	# Example: Get page HTML content
	doc = await cdp_session.cdp_client.send.DOM.getDocument(session_id=cdp_session.session_id)
	html_result = await cdp_session.cdp_client.send.DOM.getOuterHTML(
		params={'nodeId': doc['root']['nodeId']}, session_id=cdp_session.session_id
	)
	page_html = html_result['outerHTML']

	# Example: Take a screenshot using the event system
	screenshot_event = agent.browser_session.event_bus.dispatch(ScreenshotEvent(full_page=False))
	await screenshot_event
	result = await screenshot_event.event_result(raise_if_any=True, raise_if_none=True)

	# Example: pause agent execution and resume it based on some custom code
	if '/finished' in current_url:
		agent.pause()
		Path('result.txt').write_text(page_html)
		input('Saved "finished" page content to result.txt, press [Enter] to resume...')
		agent.resume()


async def main():
	agent = Agent(
		task='Search for the latest news about AI',
		llm=ChatOpenAI(model='gpt-5-mini'),
	)

	await agent.run(
		on_step_start=my_step_hook,
		# on_step_end=...
		max_steps=10,
	)


if __name__ == '__main__':
	asyncio.run(main())
```

## Data Available in Hooks

When working with agent hooks, you have access to the entire `Agent` instance. Here are some useful data points you can access:

- `agent.task` lets you see what the main task is, `agent.add_new_task(...)` lets you queue up a new one
- `agent.tools` give access to the `Tools()` object and `Registry()` containing the available actions
  - `agent.tools.registry.execute_action('click', {'index': 123}, browser_session=agent.browser_session)`
- `agent.context` lets you access any user-provided context object passed in to `Agent(context=...)`
- `agent.sensitive_data` contains the sensitive data dict, which can be updated in-place to add/remove/modify items
- `agent.settings` contains all the configuration options passed to the `Agent(...)` at init time
- `agent.llm` gives direct access to the main LLM object (e.g. `ChatOpenAI`)
- `agent.state` gives access to lots of internal state, including agent thoughts, outputs, actions, etc.
- `agent.history` gives access to historical data from the agent's execution:
  - `agent.history.model_thoughts()`: Reasoning from the model.
  - `agent.history.model_outputs()`: Raw outputs from the model.
  - `agent.history.model_actions()`: Actions taken by the agent
  - `agent.history.extracted_content()`: Content extracted from web pages
  - `agent.history.urls()`: URLs visited by the agent
- `agent.browser_session` gives direct access to the `BrowserSession` and CDP interface
  - `agent.browser_session.agent_focus`: Get the current CDP session the agent is focused on
  - `agent.browser_session.get_or_create_cdp_session()`: Get the current CDP session for browser interaction
  - `agent.browser_session.get_tabs()`: Get all tabs currently open
  - `agent.browser_session.get_current_page_url()`: Get the URL of the current active tab
  - `agent.browser_session.get_current_page_title()`: Get the title of the current active tab

## Tips for Using Hooks

- **Avoid blocking operations**: Since hooks run in the same execution thread as the agent, keep them efficient and avoid blocking operations.
- **Use custom tools instead**: hooks are fairly advanced, most things can be implemented with [custom tools](/customize/tools/basics) instead
- **Increase step_timeout**: If your hook is doing something that takes a long time, you can increase the `step_timeout` parameter in the `Agent(...)` constructor.

---
