Unable to open the requested feature

[RichardEuler]

I am continuously getting this error, once I ask Claude to test the MATLAB extension. I already tried to change to existing MATLAB Session Mode, I emptied the MATLAB Installation Path and processed in MATLAB command window:

>> matlab.engine.shareEngine
>> matlab.engine.isEngineShared (logical as 1)
>> matlab.engine.engineName (output as MATLAB_12345)

Even this did not work, after I quit Claude, restart PC.
I have no proxy servers or VPN on PC active.

The error started on MATLAB 2025b. I did not know how to solve it, so I uninstalled it and installed the new MATLAB 2026a. Nothing. Always the same error.

[sylvain-mw]

Taking Claude and the MATLAB MCP Core Server out of the equation, can you start MATLAB?

[RichardEuler]

Taking Claude and the MATLAB MCP Core Server out of the equation, can you start MATLAB?

Yes, I can start and run MATLAB normally without any issues.

[sylvain-mw]

OK, great.

So I assume that when you try to use Claude with MATLAB MCP Core Server, and --matlab-session-mode=new (the default), when MATLAB tries to start, you get the error above. Is that correct (apologies if that obvious, I just want to be sure)?

Can you then try again using --matlab-session-mode=existing, but running:

shareMATLABSession()

After having ran --setup-matlab, if you haven't already, and let me know what happens? If it doesn't work, what's the failure mode, what does the LLM report?

---

The code you mention in the issue body:

>> matlab.engine.shareEngine
>> matlab.engine.isEngineShared (logical as 1)
>> matlab.engine.engineName (output as MATLAB_12345)

Is for MATLAB Engine, and we don't make use of that.

[RichardEuler]

Here what I was basically doing.
From the last release v0.9.0 I downloaded matlab-mcp-core-server.mcpb and I uploaded to the extensions to Claude Desktop.
Then I downloaded MATLABMCPCoreServerToolbox.mltbx and then installed the toolbox on MATLAB

Inside the extension settings I set MATLAB Session Mode to new and specified the MATLAB Installation Path to C:\Program Files\MATLAB\R2025b.
It worked without any issues. I even specified the Initial Working Folder.

The first day it worked without problems and now I am still getting the error "Unable to open the requested feature".

I tried to uninstall R2025b and install R2026a, but nothing.

Now I downloaded matlab-mcp-core-server-win64.exe and through cmd I ran:

.\matlab-mcp-core-server-win64.exe --matlab-session-mode=new

I got:

{"jsonrpc":"2.0","method":"notifications/resources/list_changed","params":{}}
{"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}}

So it looks like it works.

I also ran inside MATLAB type shareMATLABSession:

function shareMATLABSession()
    %shareMATLABSession Share the current MATLAB session via MCP server
    %   This function enables sharing of the MATLAB session through the
    %   Model Context Protocol (MCP) server.

    % Copyright 2026 The MathWorks, Inc.

    mcpcoreserver.internal.shareMATLABSession();
end

So it reads the function correctly.

On Claude with the existing option I constantly seeing:

And on the extension setting with existing option:

By myself I am not a genuine programmer, so I am not really sure how to proceed.
However I really appreciate your fast reaction to the issue.

[sylvain-mw]

OK, great, thanks.

One more ask, can you run in your cmd:

.\matlab-mcp-core-server-win64.exe --matlab-session-mode=existing

And put the output here?

IMPORTANT: Please carefully review the text you would post, and remove any sensitive information there. If you see an obvious error or warning in there, you can also just post that, and cut away the rest.

[RichardEuler]

After running your code:

.\matlab-mcp-core-server-win64.exe --matlab-session-mode=existing

I got the following output:

{"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}}
{"jsonrpc":"2.0","method":"notifications/resources/list_changed","params":{}}

[sylvain-mw]

Ah, my bad, apologies, I forgot we already shipped the log suppression.

Can you run:

.\matlab-mcp-core-server-win64.exe --duplicate-logs-to-stderr --matlab-session-mode=existing

[RichardEuler]

Yes, of course. I got:

{"time":"2026-05-07T13:14:25.1904694+02:00","level":"INFO","msg":"Initiating application startup","version":"github.com/matlab/matlab-mcp-core-server v0.9.0"}
{"time":"2026-05-07T13:14:25.1915869+02:00","level":"INFO","msg":"Configuration state","LogLevel":"info","DuplicateLogsToStderr":true,"DisableTelemetry":false,"TelemetryCollectorEndpoint":"","TelemetryCollectionInterval":60000000000,"TelemetryCollectorEndpointInsecure":false,"PreferredLocalMATLABRoot":"","PreferredMATLABStartingDirectory":"","UseSingleMATLABSession":true,"InitializeMATLABOnStartup":false,"MATLABDisplayMode":"desktop","MATLABSessionMode":"existing","MATLABSessionConnectionTimeout":5000000000,"MATLABSessionDiscoveryTimeout":30000000000,"ExtensionFile":""}
{"time":"2026-05-07T13:14:25.200058+02:00","level":"INFO","msg":"Application directory state","log-dir":"C:\\Users\\<User>\\AppData\\Local\\Temp\\matlab-mcp-core-server-914472675","id":"1551000229"}
{"time":"2026-05-07T13:14:25.8620326+02:00","level":"INFO","msg":"Application startup complete"}
{"time":"2026-05-07T13:14:25.86669+02:00","level":"INFO","msg":"Added tools to MCP SDK server","count":5}
{"time":"2026-05-07T13:14:25.8678094+02:00","level":"INFO","msg":"Added additional tools to MCP SDK server","count":0}
{"time":"2026-05-07T13:14:25.8678094+02:00","level":"INFO","msg":"Added resources to MCP SDK server","count":2}
{"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}}
{"jsonrpc":"2.0","method":"notifications/resources/list_changed","params":{}}

[sylvain-mw]

OK, I'm at a loss here, nothing shows any errors. I'll need to talk with the team and circle back to you, sorry.

[RichardEuler]

I think I should apology from lack of information from my side in this regard.

[agoldsbo]

Hi, can you possibly provide the coding agent that you are using. Is it Claude Desktop (not Claude Code)? If it is, have you installed the Filesystem extension? We have experienced unexpected behaviour when this is not installed.