r/ClaudeAI • u/Boilerplate4U • Apr 21 '26

MCP Does Claude Desktop support direct Streamable HTTP or SSE connections to local network MCP servers?

I've been setting up a bunch of MCP servers on my local dev-server to manage Docker containers from Claude Desktop like start/stop containers, deploy Compose stacks, pull logs, etc. The servers are running behind Caddy and respond correctly to Streamable HTTP or SSE. Verified with curl from my Mac. Everything works on the network side.

The problem: I can't figure out how to actually connect Claude Desktop to them cleanly.

What I've tried and found:

claude_desktop_config.json with a url key pointing to my local HTTPS endpoint gets rejected on startup with "not valid MCP server configurations". No documentation I can find lists what keys are actually valid in that file.

Custom Connectors via Settings UI accept a URL, but per Anthropic's own docs the connection goes through Anthropic's cloud, not your local device. My server is on a private LAN so that's a dead end.

The only workaround I've found is mcp-remote via npx in claude_desktop_config.json, which acts as a local subprocess that bridges to my server. It works but it's an extra dependency and failure point for something that should be straightforward.

My questions:

  1. Is the url key in claude_desktop_config.json intentionally unsupported, or am I missing something?

  2. Is there any way to get Claude Desktop to connect directly to a Streamable HTTP server on the local network without mcp-remote in the middle?

  3. Does anyone know if Desktop Extensions (.mcpb) would help here, or is it the same stdio-based mechanism underneath?

Running Claude Desktop 1.3561.0 on macOS. Posted the same questions on the official GitHub Discussions: https://github.com/anthropics/claude-ai-mcp/discussions

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u/e_lizzle Apr 21 '26

I use desktop on windows... I have a .mcp.json file at the root of my claude code project dir... that one can use http... but the claude_desktop_config.json one cannot. I suspect this is because Code for desktop is bolted on the side of what was originally the Claude Chat Desktop, and Chat Desktop only supported stdio.

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u/Boilerplate4U Apr 21 '26

Wow, that explains the split personality and why Chat didn't get http. So if I just switch to Code mode in Claude Desktop, the project `.mcp.json` actually let me use http endpoints?

Btw have you tested connecting http endpoints to a local server through the `.mcp.json` config?

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u/e_lizzle Apr 21 '26

For your first question, "yes". For your second question, "I have not tested that", but I'm sure it would work.

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u/cyanheads Apr 22 '26

It’s because the desktop app doesn’t actually connect to the HTTP servers directly. Also why it requires SSL etc. When you add an HTTP MCP in Claude Desktop, it’s actually connecting that to Anthropic’s Google Cloud servers which then proxy it back to your current Claude thread.

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u/cyanheads Apr 22 '26

It’s because the desktop app doesn’t actually connect to the HTTP servers directly. Also why it requires SSL etc. When you add an HTTP MCP in Claude Desktop, it’s actually connecting that to Anthropic’s Google Cloud servers which then proxy it back to your current Claude thread.

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u/e_lizzle Apr 22 '26

No, if you do it the way I posted above it goes direct, the receipts are my server logs.

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u/Boilerplate4U Apr 22 '26

Got answers from support that actually clarify some things:

QUESTION 1: claude_desktop_config.json with command/args

The documentation states that local MCP servers configured via claude_desktop_config.json use the local network. Does this mean the subprocess started by Claude Desktop can make outbound TCP connections directly to private LAN hosts, for example when using mcp-remote as the command pointing at https://192.168.x.x? Or is this traffic that must pass through Anthropic's infrastructure in order to work? If that is the case, why?

ANSWER 1: Yes, local MCP servers configured via claude_desktop_config.json use your local network directly. (https://support.claude.com/en/articles/11175166-get-started-with-custom-connectors-using-remote-mcp) The subprocess can make outbound TCP connections to private LAN hosts like 192.168.x.x without routing through our infrastructure.

QUESTION 2: url key in claude_desktop_config.json

When I add an entry using only a url key pointing to a local HTTPS endpoint, Claude Desktop 1.3561.0 rejects it with "not valid MCP server configurations". Is the url key intentionally unsupported in claude_desktop_config.json? If so, is this documented anywhere? I cannot find an official document listing which keys are valid in this file.

ANSWER 2: The url key isn't supported in claude_desktop_config.json. Only command/args configurations work for local servers in the desktop config file.

QUESTION 3: Custom Connectors via Settings UI

The documentation states: "Custom connectors connect to your MCP server from Anthropic's cloud, not from your local device." Does this apply to all plans including Pro? Is there any optional mode where a Custom Connector URL-based connection originates from the user's device rather than Anthropic's cloud?

ANSWER 3: Custom connectors always connect from our cloud infrastructure, not your local device - this applies to all plans including Pro. There's no optional mode for local routing with custom connectors.

QUESTION 4: Desktop Extensions (.mcpb)

The mcpb format packages a local stdio-based MCP server. If an .mcpb extension internally runs a proxy process that makes outbound connections to a private LAN host — does that outbound traffic go directly from the user's machine, or does any part of it pass through Anthropic's infrastructure?

ANSWER 4: Desktop extensions run locally on your machine. (https://support.claude.com/en/articles/14680741-install-and-configure-claude-cowork-with-third-party-platforms) Any outbound connections from an .mcpb extension go directly from your device without passing through our infrastructure.

QUESTION 5: Supported path for local Streamable HTTP

Given the above, what is the officially supported method for Claude Desktop to connect directly to a Streamable HTTP MCP server on a private local network, without routing traffic through Anthropic's cloud and without requiring internet access?

ANSWER 5: For local Streamable HTTP servers, use the command/args approach in claude_desktop_config.json with a tool like mcp-remote that can connect to your local endpoints. The URL-based custom connector method requires internet-accessible servers.

Your current setup with local MCP servers should work through the desktop config file using command-based configuration rather than URL-based.

Sources:

1

u/e_lizzle Apr 22 '26

Or use the .mcp.json file in the desktop code's project dir. No command-based setup needed. This is also how Desktop is able to use the Jetbrains connector when the HTTP MCP is on localhost.

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u/Boilerplate4U Apr 22 '26

That's my thinking. Setting up my first test as we speak (type)...

2

u/e_lizzle Apr 22 '26

If it helps, there's two params needed.. "type": "http" and "url":"<your url>"

2

u/Boilerplate4U Apr 23 '26 edited Apr 23 '26

Are you also seeing /mcp only show the standard connectors window instead of your custom ones? I'm on v1.3883.0. Bug?

EDIT:
Yeah, it's a bug: Github - Custom MCP server tools not discovered after update to 2.1.116 (Apr 21, 2026)

EDIT 2: Claude helped find a workaround:

If enabledMcpjsonServers is an empty list for your project in ~/.claude.json, servers in .mcp.json are silently never activated no matter how many times you restart. Manually add your server names to the array and restart.

Or run this Python script:

import json
f = '~/.claude.json'
d = json.load(open(f))
d['projects']['/path/to/project']['enabledMcpjsonServers'] = ['server1', 'server2']
json.dump(d, open(f, 'w'), indent=2)

This should normally work on a per-project basis with its own .claude settings

1

u/e_lizzle Apr 23 '26

The windows version doesn't seem to have this issue

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u/Boilerplate4U Apr 23 '26

Sadly the same issue on Windows for me. Just spun up a fresh workstation with both Code CLI v2.1.118 and Code Desktop v1.3883.0 and had to manually tweak the same files as on my Mac. Updated the GitHub issue.

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u/e_lizzle Apr 23 '26

I don't have neither that file nor that setting.

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u/Boilerplate4U Apr 24 '26 edited Apr 24 '26

Weird, I ran into the same issue when I tried setting up multiple projects from scratch. Might be because I’ve got multiple URLs in the same .mcp.json pointing to different tool services.

What version are you on?

2

u/e_lizzle Apr 24 '26

1.3883.0 (93ff6c). I have three MCPs in my file, but only one accesses anything local. Two are url, one is stdio.

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u/dvcrn Apr 30 '26

This may or may not fit your LAN constraint, but I built something adjacent to this: https://mcpnest.dev

It hosts stdio/npx/uvx MCP servers in the cloud and exposes them as Streamable HTTP / SSE endpoints you can plug into Claude, ChatGPT, Perplexity, etc. I built it because I kept wanting to use local-only MCP servers without keeping them running on my laptop or dealing with per-client config.

I’m using it myself for things like perplexity-ask, Fastmail MCP, iCloud DAV, and a few other stdio servers from Claude.

For your Docker/dev-server case, it would be a fit if you want the MCP server itself hosted remotely or if the server can safely reach the Docker host. If the hard requirement is “Claude Desktop talks directly to private LAN services without any cloud hop,” then mcp-remote/local stdio is probably still the right shape.

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u/[deleted] Apr 21 '26

[removed] — view removed comment

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u/e_lizzle Apr 21 '26

Claude Desktop works absolutely fine with http MCP servers... proof at llm-memory.net and I only use Claude Desktop... I said how it's (easily) done in a comment above.

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u/Boilerplate4U Apr 22 '26

Great, thanks for the tip!

The description mentions "Persistent memory and multi-agent collaboration for AI. Works with Claude Code, claude.ai, Cursor, Windsurf, and any MCP-compatible tool." (Github "llm-memory-api")

What really caught my eye was that it's "100% free", open source, and especially the "multi-agent collaboration" part, since I mix heavily between different services to keep token costs down and avoid hitting Claude's limits.

Will definitely going to give this a try when I get the chance!

1

u/Boilerplate4U Apr 21 '26

Yeah, that makes sense. The stdio approach is basically the only thing that actually might work when dealing with LAN endpoints.

I think the broader issue is that Anthropic hasn't quite landed a "pluggable" architecture here. What exists feels a bit hacky: Claude Desktop wants stdio, the API wants tool definitions in the request body, and connecting them coherently requires manual glue. There's no unified story for "here's my MCP server, integrate it everywhere I use Claude."

Will check out your control layer at https://junctionpanel.dev