Headful Mode Crashes on Windows Due to Xvfb Invocation ([WinError 2] file not found)

[danielkornev]

Headful Mode Crashes on Windows Due to Xvfb Invocation ([WinError 2] file not found)

Description

When running FARA in headful mode on Windows, the agent crashes immediately with repeating errors:

[WinError 2] The system cannot find the file specified
INFO:main:Closing browser...

The crash occurs before the browser opens, and the script attempts to close the browser multiple times.

Steps to Reproduce

1. Clone the repo on a Windows machine
2. Run:

python test_fara_agent.py --headful --task "how many pages does wikipedia have" --start_page "https://www.bing.com/
" --endpoint_config "endpoint_configs/azure_foundry_config.json"

3. Observe crash

Expected Behavior

• Browser should launch in a visible headful window on Windows
• Agent should proceed with normal page navigation and task execution

Actual Behavior

• Script attempts to start Xvfb, which does not exist on Windows
• Raises:

[WinError 2] The system cannot find the file specified

• Cleanup then repeatedly tries (and fails) to stop Xvfb

Root Cause

The browser initialization logic always attempts to launch Xvfb, even on Windows.
Xvfb is a Unix-only virtual framebuffer and is not available on Windows systems.

Proposed Fix (Implemented Locally)

• Detect OS using platform.system()
• Only start Xvfb on Linux/macOS
• On Windows:
• Skip Xvfb entirely
• Allow Playwright to use native Windows display for headful mode
• Cleanup logic should only attempt to stop Xvfb on non-Windows systems

Impact

• Headful mode is currently broken on all Windows devices
• Makes debugging agent behavior impossible on Windows

Environment

• OS: Windows 10/11
• Python: 3.x
• Playwright: current version bundled with repo
• FARA version: latest main branch

Additional Notes

Here's a PR with the working fix: #19

[husseinmozannar]

Fixed now, please see windows install instructions