Firefox CDP↔BiDi Bridge

Problem

Firefox 151+ uses BiDi (not Chrome CDP) for remote debugging. The Hermes browser_* tools call agent-browser (a Node.js CLI built on Playwright), which is a Chrome CDP client — it can't speak BiDi.

Setting browser.cdp_url: http://localhost:9222 does NOT work because:

• Firefox 151 serves BiDi on port 9222, not Chrome CDP
• /json/version and /json/list Chrome endpoints return 404
• agent-browser expects Chrome CDP WebSocket protocol

Architecture

Hermes → browser_navigate → agent-browser --cdp ws://127.0.0.1:19222
                                          ↓
                    FirefoxBridge (port 19222)
                      ├── HTTP: /json/version, /json/list (Chrome CDP compat)
                      └── WebSocket: translates CDP → BiDi for Firefox
                                           ↓
                    Firefox BiDi WebSocket (port 9222)

Plugin Location

~/.hermes/plugins/browser/firefox/ contains:

• __init__.py — package marker
• provider.py — FirefoxBrowserProvider + FirefoxBridge

Prerequisites

1. Firefox must be running with --remote-debugging-port 9222
2. Hermes must have the plugin loaded

Usage

# In config.yaml:
browser:
  cloud_provider: firefox

Current Limitations

• WebSocket forwarding is echo-only (no CDP↔BiDi translation)
• To fully support all agent-browser CDP commands, the WebSocket needs a proper run_translation_loop() that maps:
  • Page.navigate → browsingContext.navigate
  • Runtime.evaluate → script.evaluate
  • Input.dispatchMouseEvent → input.performActions
  • Page.captureScreenshot → browsingContext.captureScreenshot
  • and 15+ other CDP methods to their BiDi equivalents
• See __init__.py _TRANSLATION_MAP for the starting point

Alternative: Use MCP Firefox Tools Directly

The ultimate-firefox-mcp, git-stars, and personal-intelligence MCP servers already provide Firefox-based navigate/click/type/screenshot tools. Until the CDP bridge is complete, use those MCP tools for Firefox operations.