Session Replay and Tracing

​

Browser Agent Observability

One of the most powerful features of using Index is its built-in tracing and observability. Both in the open source package and in the Index API, you get:

1. Full Browser Session Replay: Watch exactly what the browser agent saw and did during execution
2. Synchronized Traces: See the agent’s internal reasoning process alongside browser actions
3. Performance Metrics: Track duration, token usage, and other performance indicators
4. Error Analysis: Easily identify and debug failures or unexpected behaviors

​

Setup

To enable browser agent observability, you simply need to initialize Laminar tracing before running the agent. You can do this by calling Laminar.initialize() at the start of your application. You can also set the LMNR_PROJECT_API_KEY environment variable instead of passing it directly.

import { Laminar } from '@lmnr-ai/lmnr';

// Initialize Laminar with your project API key
Laminar.initialize({ projectApiKey: "YOUR_PROJECT_API_KEY" });

import { Laminar } from '@lmnr-ai/lmnr';

// Initialize Laminar with your project API key
Laminar.initialize({ projectApiKey: "YOUR_PROJECT_API_KEY" });

from lmnr import Laminar

# Initialize tracing with your project API key
Laminar.initialize(project_api_key="YOUR_PROJECT_API_KEY")

All browser agent activities will automatically be traced and recorded in the Laminar platform, where you can access the session replays and analysis. You can access session recordings in the traces tab of the Laminar platform.

​

Visualizing Browser Agent Sessions

The Laminar platform provides a comprehensive visualization interface where you can:

• Watch time-synced recordings of what the browser agent saw and interacted with
• Follow the agent’s thought process and decision-making
• Review extracted data and final outcomes
• Debug issues by identifying exactly where and why things went wrong
• Speed up session replays up to 8x for faster debugging

This visual replay gives you unprecedented insight into how the browser agent interprets and executes your instructions, making it easier to refine your prompts and build robust web automation workflows.

​

Learn More

Learn more about tracing on Laminar here.