bug: MCP Connection Closed Error After Upgrading to v0.27.3

[paulreijnierse]

Description

The Taskmaster MCP server connection is consistently closing/failing after upgrading to version 0.27.3, resulting in "{"error":"MCP error -32000: Connection closed"}" and "Not connected" errors for all MCP tools. When I disable and enable the mcp in Cursor settings it shows all the toolcalls, but when Cursor executes one I only get the error. On a second toolcall after this I see "{"error":"Not connected"}"

This did not happen for me on previous versions (I ran 0.27.2 before). I updated the mcp.json to follow the latest setup (without the --package setup). I restarted Cursor and even my machine but the behaviour remains consistent.

The cli works just fine.

Steps to Reproduce

1. Open Cursor IDE with Taskmaster MCP server configured
2. Attempt to use any Taskmaster MCP tool (e.g., get_task, add_subtask, set_task_status)
3. Error occurs consistently across all MCP tool calls

Expected Behavior

MCP tools should work reliably without connection drops. Expected commands like mcp_taskmaster-ai_get_task, mcp_taskmaster-ai_add_subtask, etc. should execute successfully and return proper responses.

Actual Behavior

All MCP tool calls fail with one of these errors:
MCP error -32000: Connection closed Not connected
The connection appears to drop after any operation.

Screenshots or Logs

{"error":"MCP error -32000: Connection closed"}
{"error":"Not connected"}

Environment

• Task Master version: 0.27.3
• Node.js version: v22.12.0
• Operating system: macOS (darwin 23.6.0)
• IDE (if applicable): Cursor version: 1.7.33

[github-actions]

Found 1 possible duplicate issue:

1. feedback: Odd MCP behaviour in Cursor with TM #984

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[Crunchyman-ralph]

Mind giving me more context for this, can you give me what your mcp.JSON looks like?

Did you try any other IDEs or tools with the same mcp config ?

[Crunchyman-ralph]

Can you get the logs of the mcp somehow (output tab on cursor)

[paulreijnierse]

Alright this is very strange, I used another mcp that was configured through Cursor and it worked instantly. After that the mcp for taskmaster also worked again. Would you like me to investigate this a bit further or just treat it as a weird combination of circumstances @Crunchyman-ralph ?

[paulreijnierse]

Alright, so I was a bit too quick there, the update_task worked, but when add_subtask runs it immediately fails again. The only response Cursor shows is:
{"error":"MCP error -32000: Connection closed"}

I tried some more and it seems to be happening with some of the tools and not with others. The connection gets closed with add_subtask and remove_subtask. But not with get_tasks, get_task, update_subtask, set_task_status.

The add_subtask and remove_subtask do get executed, but the only response I get from those is {"error":"MCP error -32000: Connection closed"} after which I need to manually enable the mcp again to make it work again.

I dug into the logs and I see the following:

2025-10-04 10:43:32.198 [info] Handling CallTool action for tool 'add_subtask'
2025-10-04 10:43:32.198 [info] Calling tool 'add_subtask' with toolCallId: tool_75d99fdd-dde9-4ae5-98a4-a488312e3d3
2025-10-04 10:43:32.210 [error] Error generating task files: Cannot read properties of null (reading 'toString')

2025-10-04 10:43:32.210 [error] Error generating task files: Cannot read properties of null (reading 'toString')

2025-10-04 10:43:32.219 [info] Client closed for command
2025-10-04 10:43:32.219 [error] Error calling tool 'add_subtask': MCP error -32000: Connection closed

And for the remove_subtask:

2025-10-04 10:59:39.211 [info] Calling tool 'remove_subtask' with toolCallId: tool_a31a1bbf-eb8f-4bf6-8b55-0f6424b6a81
2025-10-04 10:59:39.224 [error] Error generating task files: Cannot read properties of null (reading 'toString')

2025-10-04 10:59:39.224 [error] Error generating task files: Cannot read properties of null (reading 'toString')

2025-10-04 10:59:39.234 [info] Client closed for command
2025-10-04 10:59:39.234 [error] Error calling tool 'remove_subtask': MCP error -32000: Connection closed

[Crunchyman-ralph]

alright, may I ask if its just add_subtask that breaks, how does add_task work in terms of tooling ?

What I think is happenning is that there is a console log thats being logged in one of the tools which breaks the stdio mcp server, and so the next tool call will fail.

So if I can just get that answer from you like, which tools are causing the next tool to fail, it would be much appreciated

[Crunchyman-ralph]

@claude seems like we're trying to generate task files, but we no longer support that (no longer call that function) so maybe wherever this is being called, you can just remove that call from the code.

Please apply to all commands and all mcp tools calls, scripts/modules/... and mcp-server/src/...

[claude]

Claude finished @Crunchyman-ralph's task —— View job • claude/issue-1271-20251005-1915 • Create PR ➔

---

Fixed MCP Connection Issues ✅

Successfully identified and removed deprecated task file generation calls that were causing MCP connection drops with add_subtask and remove_subtask tools.

Todo List:

• Search for "generate task files" functionality in the codebase
• Identify specific calls in MCP server code (mcp-server/src/)
• Search for related calls in scripts/modules/
• Remove deprecated calls from add_subtask functionality
• Remove deprecated calls from remove_subtask functionality
• Remove deprecated calls from move_task functionality
• Verify other MCP tools aren't affected
• Test changes and commit fixes

Root Cause Found & Fixed:

The error Cannot read properties of null (reading 'toString') was occurring in /scripts/modules/task-manager/generate-task-files.js:36 where the code tried to access rawData[tag] with a null/undefined tag parameter.

Changes Made:

• scripts/modules/task-manager/add-subtask.js: Removed generateTaskFiles() call and import
• scripts/modules/task-manager/remove-subtask.js: Removed generateTaskFiles() call and import
• scripts/modules/task-manager/move-task.js: Removed generateTaskFiles() calls and import

The generateTaskFiles() functionality is no longer supported as mentioned by @Crunchyman-ralph, so these calls have been replaced with explanatory comments.

Testing:

With these changes, the add_subtask and remove_subtask MCP tools should no longer cause "MCP error -32000: Connection closed" errors. The tools will continue to function normally for task manipulation, just without the deprecated file generation step.

---

[paulreijnierse]

alright, may I ask if its just add_subtask that breaks, how does add_task work in terms of tooling ?

What I think is happenning is that there is a console log thats being logged in one of the tools which breaks the stdio mcp server, and so the next tool call will fail.

So if I can just get that answer from you like, which tools are causing the next tool to fail, it would be much appreciated

I can confirm that add_task, expand_task, update_task, clear_subtasks work as expected. So far I've only seen the issue with add_subtask and remove_subtask. So could be that the fix provided by Claude is exactly what is needed here.