freema/firefox-devtools-mcp

v0.9.2 Breaking

This release includes 1 breaking change for platform teams planning a safe upgrade.

Published 1mo MCP Browser & Automation

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✓ No known CVEs patched

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✓ No known CVEs patched in this version

Topics

claude-code firefox mcp mcp-server

Affected surfaces

auth breaking_upgrade

Summary

AI summary

Removed the --marionette-host CLI parameter and switched connect‑existing mode to use Selenium's native --connect-existing feature.

Full changelog

Added

evaluate_privileged_script now detects const/let/var statements and rejects them with a helpful error message suggesting IIFE workaround
BiDi console and network events now degrade gracefully when Firefox Remote Agent is not running, instead of crashing
Comprehensive e2e scenario integration tests covering the full FirefoxClient API
Unit tests for privileged context state consistency and statement detection
Testing documentation (docs/testing.md)

Fixed

Privileged context state not preserved across tool calls: set_firefox_prefs and list_extensions no longer silently revert a privileged context selection
Session cleanup on connection failure: getFirefox() now closes the failed instance to prevent zombie geckodriver processes and Marionette session locks

Changed

Breaking: Removed --marionette-host CLI parameter (connect-existing mode now uses localhost only)
Rewrote connect-existing mode to use Selenium's native --connect-existing feature via ServiceBuilder, replacing the custom GeckodriverHttpDriver HTTP client (~530 lines removed)
Replaced custom IDriver/IElement/IBiDi interfaces with native WebDriver/WebElement from selenium-webdriver
Improved error messages for BiDi-dependent features (console/network) to suggest --remote-debugging-port
Pinned all dependency versions for build reproducibility
Updated dependencies: @modelcontextprotocol/sdk 1.29.0, tsup 8.5.0, tsx 4.21.0, typescript-eslint 8.58.0

Full Changelog: https://github.com/mozilla/firefox-devtools-mcp/compare/0.9.1...0.9.2

Breaking Changes

Removed `--marionette-host` CLI parameter; connect‑existing mode now binds to localhost only.

View diff on GitHub

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About freema/firefox-devtools-mcp

Firefox browser automation via WebDriver BiDi for testing, scraping, and browser control. Supports snapshot/UID-based interactions, network monitoring, console capture, and screenshots.

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