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[0w0-dot]

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Currently, when using MCP on the Claude desktop, an error like "Error executing code: Cannot convert undefined or null to object" occurs, and a solution is needed.

claude say :

Error Occurrence Situation

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Currently Detected Error: Error executing code: Cannot convert undefined or null to object Error Occurrence Patterns:

✅ edit-file-lines:get_file_lines - Working normally
❌ terminal:execute_command - Error occurred
❌ git:git_status - Error occurred
❌ edit-file-lines:search_file - Error occurred

Suspected Root Causes:

MCP tool initialization issues
Permission or path access problems
Windows path handling complications
Null/undefined parameter passing in MCP protocol
Command execution environment misconfiguration

Error Pattern Analysis:

File reading operations: Functional
System command execution: Failing
Git operations: Failing
File search operations: Failing

Technical Details:

Error Type: JavaScript TypeError
Location: MCP tool parameter processing
Impact: Limited to system-level operations
Workaround: Use file-based operations only

I don't really know what's going on

[0w0-dot]

Thank you so much! If it's okay, would you mind sharing your kind answer with other friends in Korea? Thanks again for your reply. 2025년 7월 23일 (수) 오후 5:23, johnavgeros ***@***.***>님이 작성:

…

I've got the same issue... — Reply to this email directly, view it on GitHub <#167221 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BUSUSCD6ITUEFWF76EQMP633J5BA7AVCNFSM6AAAAACCE3QZYCVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTGOBWGAZTMMI> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[bureaucreative]

what was the solution ? please share :)

[cakebake]

Currently, when using MCP on the Claude desktop, an error like "Error executing code: Cannot convert undefined or null to object" occurs, and a solution is needed.
...
I don't really know what's going on

The same in Claude.ai (web). Same error message. I wasted my time in debugging my MCP server for 2 hours, but it is definitely with Claude. ^^

10% success at MCP Call each inference - 90% fail. Local MCP client: 100% success.

It´s something about the tool parameters...

[jcmullwh]

For me, first tool call after MCP server startup works fine then subsequent calls then "Error executing code: Cannot convert undefined or null to object" for all after the first. This is for both my custom mcp server and an unmodified open source server. Both run locally w/STDIO.

[SobieskiCodes]

It depends on the command I'm running. For example, ls -la seems to work every time, but ls -la resources/ fails every time.

[Kvintus]

Same error happening here

[SobieskiCodes]

also getting it using
https://github.com/steipete/claude-code-mcp
with claude desktop Cannot read properties of undefined (reading 'replaceAll') seems to be my root cause.

[TheChesireCat]

I think there's a service disruption at Anthropic (I get the same error with opus and sonnet)

[Shtono]

I am using Claude Desktop connected to Webstorm via MCP server, I am having the same issues in the past hour, couldn't solve the problem , but found out that Claude is having issues reading files of my project, which could be solved by opening that file in editor and asking it to try again. It is a nasty solution, but I have nothing better at the moment, hopefully this get's resolved quickly.

[Mycosystema]

I got the same thing with the Notion API : Error executing code: Cannot convert undefined or null to object.

[soonjune]

Getting the same error for a response well defined in json.

[CharlesTBetz]

confirming this is an issue affecting most/all of my MCP use.

[MirkoSon]

same here, glad I'm not alone.

[redmorestudio]

solidarity! I thought I was going crazy. I've tried installing new mcp servers, different models - it works once then dies.

Ok, I'm on a Mac. I'm running sequoia 15.4. I'm using mac silicon. How about y'all?

[redmorestudio]

Ok, this is what anthropic support has to say. I'm not loving the "configuration error" part - it's like, no, my configuration didn't just die overnight...

The "Cannot convert undefined or null to object" error with MCP server filesystem operations is a known issue affecting several users. While I don't have full information about the specific root cause, this appears to be related to connection stability and state management issues in Claude Desktop.
Immediate troubleshooting steps:
Restart Claude Desktop completely - Don't just close the window, fully quit and restart the application
Check your MCP configuration - Verify commands and paths in your configuration file for syntax errors
Review connection stability - Long-running operations (>10 seconds) can cause timeouts and disconnections
Check logs for detailed error information:
• macOS: ~/Library/Logs/Claude/mcp*.log
• Windows: %APPDATA%\Claude\Logs\mcp*.log
Workaround for critical work:
Make git commits between messages when working on important code, as MCP connection failures can cause Claude Desktop to revert conversations to previous states, potentially losing your work.
Additional considerations:
Ensure all required dependencies are installed
Check for conflicts between multiple MCP servers
Verify the server process can start correctly
The system status shows no current incidents affecting MCP functionality, suggesting this is likely a configuration or local environment issue rather than a service-wide problem.

[MirkoSon]

local environment my ass :D
I didn't change anything and I'm on Windows 11 - Claude Desktop. Same config as always. Are we all visionaries?

[redmorestudio]

ok, so, in the space of me jamming information down their throats - this happened - it's moved to being a "system-wide" issue:

Since this is an active system-wide incident rather than a local configuration issue, the problem should resolve once we complete our investigation. You can track the status at https://stspg.io/b4zv4jzkltpd for updates.

[TimePoor]

Based on utc-9, July 23
I was confronted with this issue from around 4 p.m. and spent about eight hours debugging, complaining to Claude's support team, but it was almost 2 a.m. and we went into investigation
I even reinstalled windows to fix this problem, but it didn't work out.
I hope it's resolved soon

[redmorestudio]

"Identified
The issue has been identified and a fix is being implemented.
Posted 14 minutes ago. Jul 23, 2025 - 17:16 UTC"

[redmorestudio]

So, since we're all here - I'd just like to say that we all hit anthropic support and say "look, if multiple users, across multiple time zones, with multiple different systems are reporting the same issue - don't call it 'configuration error' or 'local problem' or 'pilot error' - this should be a clue that something is wrong on your side, not ours." I know that I'm going to say something - and I'd encourage all of you to do so as well.

[redmorestudio]

"this issue has been resolved". Ok, then, back on the horse. :)