Claude Desktop: MCP servers fail with Protocol instance reuse error
Resolved 💬 22 comments Opened Feb 21, 2026 by cpinto Closed Feb 24, 2026
Bug Description
Claude Desktop v1.1.3918 on macOS shows error toasts on every launch:
- "Could not connect to MCP server mcp-registry"
- "Could not connect to MCP server Claude in Chrome"
Root Cause
The actual error from claude.ai-web.log is identical for both servers:
[MCP] Could not connect to MCP server mcp-registry Error: Error invoking remote method 'connect-to-mcp-server': Error: Already connected to a transport. Call close() before connecting to a new transport, or use a separate Protocol instance per connection.[MCP] Could not connect to MCP server Claude in Chrome Error: Error invoking remote method 'connect-to-mcp-server': Error: Already connected to a transport. Call close() before connecting to a new transport, or use a separate Protocol instance per connection.The app connects three MCP servers on startup (Filesystem, mcp-registry, Claude in Chrome). The Filesystem extension connects successfully, but the other two fail because the Protocol instance is being reused instead of creating separate instances per connection.
This is a race condition — all three connection requests fire at the same timestamp, and the shared Protocol instance can only handle one.
Steps to Reproduce
- Install Claude Desktop v1.1.3918 on macOS
- Have the Filesystem extension installed (from the extension registry)
- Launch the app
- Observe error toasts for mcp-registry and Claude in Chrome
Environment
- App version: 1.1.3918 (commit a4b368d308b05c425b74c1c19ed47a572d3a90f6)
- Platform: macOS (darwin arm64, Apple M2)
- OS: Darwin 25.2.0
Notes
- The errors are not caused by misconfiguration —
mcpServersinclaude_desktop_config.jsonis empty. Both mcp-registry and Claude in Chrome are built-in servers. - Disabling the Chrome extension in settings and removing the
chromeExtensionpairing data from config does not fix it. - The Filesystem MCP server works correctly despite the errors.
- The errors reproduce on every single launch and on every new conversation.
22 Comments
FYI happening on Windows as welllll. Getting it everywhere
Another here with it on MacOS
ditto on mac
Hey everyone, we are currently investigating. The mcp-registry is an internal MCP and it is still functional even though the error pops up. Will be gone in the next release on Monday. Appreciate your patience!
<img width="792" height="234" alt="Image" src="https://github.com/user-attachments/assets/9236f6e3-6b23-43de-9752-20527bbc373e" />
The same issue — I even thought it was caused by my own VPN.
I've been having this since forever. I think it also breaks other stuff because as soon as this error pops up, the top center tab selector where Cowork and Claude Code can be selected disappears. So this breaks Claude Desktop quite a bit for me.
Same issue in Windows 10 with Claude Desktop 1.1.40 installed today via official website.
same issue on Win11 with Claude Desktop 1.1.4010
Same issue here.
MacOS 15.7.4 (24G517)
Claude 1.1.4010 (da63f3) 2026-02-22T18:53:52.000Z
Same here, macOS v26.3. Macbook and Mac mini. Claude 1.1.4010 (da63f3) 2026-02-22T18:53:52.000Z and a few earlier versions.
In some instances I also get "This conversation is too long to continue. Start a new chat, or remove some tools to free up space." when I shouldn't. If I switch to web/iOS, I can continue.
Web and iOS version works fine.
Seeing the same issue on Windows 11 Pro, Version 25H2, OS Build 26200.7840 (installed 2026-02-18). Claude Desktop v1.1.4010 (da63f3). Config is empty — no user-defined mcpServers, only sidebarMode: "code" in claude_desktop_config.json. Both error toasts ("Could not connect to MCP server mcp-registry" and "Could not connect to MCP server Claude in Chrome") appear on every new conversation. Sustained high CPU usage on a single core even when idle, causing excessive fan activity.
Possibly related to CF issues today?
Experiencing the same issue on the latest version.
Steps taken:
The issue persists across app restarts. Happy to provide logs if needed.
Experiencing same issue on Windows 11.
Claude Desktop latest version. Tried to integrate with DockerDesktop MCPs and constantly getting this error. I have tried :
1 : Reinstalling claude.
2 : Adding node paths in env variables.
3 : Added all mcp servers in claude config file in AppData -> Roaming.
I've been using Claude Desktop on Mac for several months and have never seen this error before. Today I switched to installing Claude from Homebrew and this error appeared for the first time. I'm not sure if that's coincidence or causal. I did try restarting with all related config/data dirs deleted (
~/Library/Application Support/Claude,~/Library/Logs/Claude,~/.claude), but the issue remains.Still having this issue on Mac. Reinstalled Chrome Claude Extension and Reinstalled Claude Desktop App (CoWork). Didn't help. On the latest version of Claude Desktop for Mac.
+1 — experiencing the same issue on macOS with a Teams account. Subscribed for updates on the fix.
Hey everyone, we just released a new version of desktop, it should be fixed if you upgrade to the latest Claude 1.1.4088 (7e63fd) 2026-02-23T21:25:53.000Z.
Thanks for the reports! Please tag me if you see the error again and I can re-open the issue to investigate
@alicelovescake The error is gone on my end, but the Cowork tab still isn’t visible. I only see the Cowork settings screen.
My build: Claude 1.1.4173 (12766c) 2026-02-24T15:04:14.000Z
Hey @royguillaum hopefully you can see your cowork tab now? We had a temporary glitch yesterday with rendering the tabs that should be resolved.
Working!
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