hermes - 💡(How to fix) Fix [Bug]: browser_console crashes with CDP "Object reference chain is too long" when returning DOM Elements [1 pull requests]

Bug Description

When the LLM uses the browser_console tool and its injected JavaScript returns a raw DOM Node or NodeList (e.g., return document.body), it causes a fatal CDP serialization crash instead of returning a graceful tool error. Proposed Fix: Update _browser_eval in tools/browser_tool.py to wrap the incoming expression in an IIFE that explicitly checks if the returned result is an instance of Node or Window. If it is, it should return a clean string like "TOOL_ERROR: Extract primitive values instead" to guide the LLM back on track. Proposed Fix (Tested Locally): In tools/browser_tool.py, update the _browser_eval function to wrap the incoming expression in an IIFE that safely checks the result before returning it to the CDP protocol: safe_expression = f""" (() => {{ const result = (function() {{ {expression} }})(); if (result instanceof Node || result instanceof NodeList || (typeof Window !== 'undefined' && result instanceof Window)) {{ return "TOOL_ERROR: You cannot return raw DOM Elements. Please extract and return primitive values like .innerText or .href instead."; }} return result; }})() """

Steps to Reproduce

. Start an active Hermes agent session with the browser tools enabled. 2. Tell the agent to run the following exact command: browser_console(expression="document.body") 3. Observe the output. Instead of getting a graceful TOOL_ERROR, the underlying CDP connection will crash completely, throwing a raw "Object reference chain is too long" exception back to the agent.

Expected Behavior

When the LLM uses the browser_console tool and its injected JavaScript returns a raw DOM Node or NodeList (e.g., return document.body), it causes a fatal CDP serialization crash instead of returning a graceful tool error

Actual Behavior

. Start an active Hermes agent session with the browser tools enabled. 2. Tell the agent to run the following exact command: browser_console(expression="document.body") 3. Observe the output. Instead of getting a graceful TOOL_ERROR, the underlying CDP connection will crash completely, throwing a raw "Object reference chain is too long" exception back to the agent.

Affected Component

Tools (terminal, file ops, web, code execution, etc.)

Messaging Platform (if gateway-related)

No response

Debug Report

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  • Recent log lines (agent.log, errors.log, gateway.log — may contain
    conversation fragments and file paths)
  • Full agent.log and gateway.log (up to 512 KB each — likely contains
    conversation content, tool outputs, and file paths)

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Operating System

Windows

Python Version

3.11

Hermes Version

0.15.0

Additional Logs / Traceback (optional)

Root Cause Analysis (optional)

No response

Proposed Fix (optional)

No response

Are you willing to submit a PR for this?

• I'd like to fix this myself and submit a PR