[BUG] Desktop Extension MCP servers not passed to Cowork VM despite being enabled in session config

[Klizzy]

Bug Report

Product: Claude Desktop (macOS)
Version: 1.1.3189 (1b7b58) — 2026-02-14T00:09:46.000Z
Related Issues: #20377 (closed as completed on Feb 14, but issue persists)

Description

Desktop Extension MCP servers (Filesystem, Context7, Control your Mac) are enabled and running correctly in Claude Desktop Chat mode, but are not forwarded to Cowork VM sessions. The --mcp-config argument passed to the Claude process inside the VM only includes SDK-type servers (Claude in Chrome), completely omitting all desktop extension MCP servers.

The session metadata (enabledMcpTools in the session JSON) correctly lists all local MCP tools as enabled, but the VM process spawner ignores them when constructing the --mcp-config and --allowedTools arguments.

Steps to Reproduce

1. Install desktop extension MCP servers (e.g., Filesystem, Context7, Control your Mac) via Claude Desktop Extensions
2. Verify they show as "status": "running" in ~/Library/Logs/Claude/mcp-info.json
3. Verify tools work correctly in Claude Desktop Chat mode (they do)
4. Open a new Cowork session
5. Ask Claude to list its available MCP tools

Result: Only mcp__Claude_in_Chrome__* tools are available. No Filesystem, Context7, or Control your Mac tools.

Expected Behavior

All enabled desktop extension MCP servers should be available to the Cowork VM, matching the enabledMcpTools configuration in the session JSON. The --mcp-config passed to the VM Claude process should include entries for Filesystem, Context7, and Control your Mac alongside the SDK-type servers.

Actual Behavior

The --mcp-config argument passed to the VM process only includes SDK-type servers:

{"mcpServers":{"Claude in Chrome":{"type":"sdk","name":"Claude in Chrome"}}}

Desktop extension servers are completely absent. Evidence from cowork_vm_node.log:

Current sessions (Feb 17, build 3189):

--allowedTools Task,Bash,Glob,Grep,Read,Edit,Write,NotebookEdit,WebFetch,TodoWrite,WebSearch,Skill,
mcp__mcp-registry__search_mcp_registry,mcp__mcp-registry__suggest_connectors,
mcp__plugins__search_plugins,mcp__plugins__suggest_plugin_install,
mcp__scheduled-tasks__list_scheduled_tasks,mcp__Claude_in_Chrome

--mcp-config {"mcpServers":{"Claude in Chrome":{"type":"sdk","name":"Claude in Chrome"}}}

No mcp__Filesystem__*, mcp__Context7__*, or mcp__Control_your_Mac__* in --allowedTools.
No Filesystem, Context7, or Control your Mac entries in --mcp-config.

Meanwhile, the session JSON correctly has them all enabled:

"enabledMcpTools": {
    "local:Filesystem:edit_file": true,
    "local:Filesystem:read_file": true,
    "local:Filesystem:write_file": true,
    "local:Context7:get-library-docs": true,
    "local:Context7:resolve-library-id": true,
    "local:Control your Mac:osascript": true
    // ... all set to true
}

Additionally, the situation has regressed over successive builds. Older sessions (pre-Feb 13) at least included mcp-registry and cowork SDK servers in the config:

// Pre-Feb 13:
{"mcpServers":{"Claude in Chrome":...,"mcp-registry":...,"cowork":...}}

// Feb 17 (current):
{"mcpServers":{"Claude in Chrome":...}}

Troubleshooting Attempted

• Confirmed all 3 MCP servers show "status": "running" in mcp-info.json
• Confirmed all 3 servers initialize successfully in mcp.log (handshake, tool listing, no errors)
• Confirmed tools work correctly in Claude Desktop Chat mode
• Fully quit (Cmd+Q) and relaunched Claude Desktop
• Opened fresh Cowork sessions — same result
• Checked cowork_vm_node.log — confirmed --mcp-config never includes desktop extension servers

Environment

• OS: macOS ARM (Apple Silicon)
• Claude Desktop: 1.1.3189 (1b7b58) — built 2026-02-14
• MCP Server Transport: stdio (via desktop extensions)
• Affected Servers:
  • Filesystem (ant.dir.ant.anthropic.filesystem) — Node-based
  • Context7 (context7) — Node-based
  • Control your Mac (ant.dir.gh.k6l3.osascript) — Node-based
• Works in: Claude Desktop Chat mode
• Broken in: Cowork mode (all sessions)

Additional Context

• Issue [BUG] COWORK || Local / desktop MCP tools not exposed to claude cowork, all the tools work properly in claude chat #20377 was closed as completed on Feb 14, 2026, but this build (also from Feb 14) still exhibits the exact same problem.
• The mcp-info.json config and mcp.log confirm all servers are running and healthy on the host side — the issue is exclusively in how the Cowork VM spawner constructs the --mcp-config argument.
• The enabledMcpTools session metadata proves the Desktop app knows about these tools and marks them as enabled — it just doesn't pass them through to the VM process.
• All affected servers are Node-based desktop extensions using stdio transport. The only server that works in Cowork (Claude in Chrome) uses type: "sdk" (internal IPC bridge).

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] COWORK || Local / desktop MCP tools not exposed to claude cowork, all the tools work properly in claude chat #20377
2. [BUG] Local MCP Servers Still Not Working in Cowork Mode (v1.1.2102) #23424
3. [BUG] Local MCP servers still unavailable in Cowork as of 1.1.1093 (5a5517) #21440

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
• To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

[Klizzy]

Those are related issues, but it seems they still persist or were introduced again. Here are some additional logs:

mcp.log
session-enabledMcpTools.json
cowork-vm-node-spawn.log
mcp-info.json

[dgelman1]

I believe I'm dealing with a related issue on Windows 11.

Installed Metabase MCP from the Claude extension library and it works just fine in Claude Chat, but I'm getting the error:
Missing user:mcp_servers scope and the current Cowork session only has user:inference scope.

Version: Claude 1.1.3363 (ee4247) 2026-02-17T15:55:21.000Z

[Klizzy]

After the recent update to Claude 1.1.4328 (d8e391) 2026-02-25T17:04:36.000Z , the build in chrome and newly added scheduled tasks are working within cowork, but custom node based local one still don't work within cowork.

The custom one listed above, so context7 and Control your Mac seem not to be passed / bridged into the cowork VM.

MCP Server	Status	Notes
Claude in Chrome	✅ Working	Full tool access — tabs, navigation, screenshots, etc.
Filesystem	✅ Working	Can mount directories and read/write files via mcp__cowork__ tools
Context7	❌ No tools exposed	Not available in Cowork
Control your Mac	❌ No tools exposed	Not available in Cowork

[francoios]

ey @Klizzy,

I’m currently working on a Unity server MCP. It’s been working fine on my end (it’s actually been working since I started building it about four days ago). It was originally set up in Node, but I migrated it to MCPB following your latest message.

Unfortunately, I can’t get it to work for the rest of my team. Claude doesn’t detect it on their side and it doesn’t appear in the list of available connectors. However, on my end, it shows up correctly under Extensions → Developer.

Do you have any idea what might be causing this discrepancy?

[Klizzy]

Hello @francoios ,

was your MCP server running locally successfully within a cowork session, or only inside regular claude desktop chats- and code?

Remote MCP servers seems to work for some users, based on some related GH issues comments.

[francoios]

Actually i found out the issue with most of the MCP that weren't working.

It's related to maximum amount of tools, which is approx 40 within an MCP, so if you experience the same issue, it's mostly because of that.

Implementing a Proxy + lazy loading fix the thing !

[Klizzy]

Actually i found out the issue with most of the MCP that weren't working.

It's related to maximum amount of tools, which is approx 40 within an MCP, so if you experience the same issue, it's mostly because of that.

Implementing a Proxy + lazy loading fix the thing !
@francoios

That's nice to hear and good to know. In my case the total tool amount is ~6, so it seam that is related to something else - at least for my case.

[freeformz]

I'm running into this on Claude Desktop on MacOS (Claude 1.1.5368 (d12d02) 2026-03-05T17:29:33.000Z) and a bunch of the stuff I want to do requires mcps :-(

[freeformz]

After the session starts -- I can say "no really the is installed and running" and it's like "oh! you're right".

This obv doesn't work for scheduled tasks to behave properly though when those tasks rely on the mcp. I've even adjusted the prompts to add: IMPORTANT: The <mcp server> is installed, use it.