Jev Ultrafast (Browser Use)

What is Jev Ultrafast?

Jev Ultrafast is an ultra-high-speed autonomous web agent framework created through a collaboration between Browser Use (the creators of the popular open-source browser automation agent) and TypeSafe. Engineered to resolve the notorious latency and fragility of traditional vision-based browser agents, Jev Ultrafast introduces a dynamic, indexed action space combined with a dual-head decision policy. In live real-world benchmarks, the agent completes an end-to-end flight search workflow on Google Flights (Zürich to London) in just 7.07 seconds at 1× real-time speed, including live text generation, dynamic dropdown selection, and full page loading waits.

Key Features & Technical Innovations

• Dynamic Indexed Action Space: Converts real-time DOM observations into structured, numbered element tables (e.g. [1] button, [2] combobox, [3] textbox), ensuring the model only acts upon valid, actionable targets.
• Single-Round-Trip Dual-Head Decisions: Powered by TypeSafe Jev. A single model request predicts both the operation (CLICK, TYPE_TEXT, SELECT, SCROLL_UP, SCROLL_DOWN, WAIT, DONE, BLOCKED) and the speculative target index simultaneously, cutting network round trips in half.
• Decoupled Asynchronous Text Generation: Text input is generated only when the chosen operation is TYPE_TEXT, using an ultra-fast compact LLM (such as Mercury 2.5, DeepSeek, GLM, or Gemini), eliminating heavy token generation overhead during click navigation.
• 90.7% Reduction in Protocol Overhead: Optimized DOM snapshotting and event-driven combobox waiting reduces browser protocol calls from 1,092 down to just 101 per task, slashing median Jev decision latency to 178 ms.
• Visual Inspector & Debugging UI: Built-in local web dashboard at http://127.0.0.1:8766 displaying element tables, operation probabilities, target distributions, and step-by-step action replays.
• Robust Chrome CDP Connection: Connects natively via Browser Harness with full remote debugging support, cookie persistence, and headless or headed browser execution.

Benchmark: Live Google Flights Workflow Performance

Quickstart & Local Setup

1. Clone & Install Dependencies:

   git clone https://github.com/browser-use/jev-ultrafast.git
   cd jev-ultrafast
   uv sync

2. Configure Credentials: Copy .env.example to .env and add your TYPESAFE_API_KEY and TEXT_MODEL_API_KEY (OpenRouter, Gemini, or DeepSeek).
3. Launch the Visual Inspector:

   uv run jev

   Open http://127.0.0.1:8766 to watch autonomous navigation in real time.

Python Library Integration

from jev_ultrafast import Agent

with Agent(
    "https://www.google.com/travel/flights?hl=en",
    "Find one-way flights from Zurich to London on September 20, 2026, for one adult in economy."
) as agent:
    agent.run()

Technical Specifications

Frequently Asked Questions