[BUG]: Remote MCP servers crash in Docker — Node 18 + undici 7.x incompatible

[miraculix95]

How are you running AnythingLLM?

Docker (mintplexlabs/anythingllm:1.12.1, also reproduces on 1.11.1)

What happened?

Configuring any remote MCP via the mcp-remote bridge (the documented pattern, e.g. for Linear) results in immediate child-process crash on AnythingLLM trying to spawn the MCP server:

/app/.npm/_npx/.../node_modules/undici/lib/web/webidl/index.js:537
webidl.is.File = webidl.util.MakeTypeAssertion(File)
                                                ^
ReferenceError: File is not defined
    at Object.<anonymous> (/app/.npm/_npx/.../node_modules/undici/lib/web/webidl/index.js:537:48)
    ...
Node.js v18.20.8

In the MCPHypervisor logs this surfaces as Transport closed / MCP error -32000: Connection closed for every mcp-remote-based server entry.

Root cause

• AnythingLLM Docker pins node_18.x in docker/Dockerfile (both v1.11.1 and v1.12.1, NodeSource repository).
• mcp-remote@0.1.38 (the bridge package recommended in the docs for remote MCP servers) depends on undici@^7.12.0.
• undici 7.x npm-manifest declares "engines": { "node": ">=20.18.1" }.
• undici 7.x references the File global at module-load time; that global only exists in Node 20+. In Node 18 it is undefined, so the module import itself crashes — before any AnythingLLM code can recover.

The crash is not endpoint-specific: it reproduces identically against Linear's hosted MCP, a self-hosted FastMCP endpoint, and any other URL passed to mcp-remote.

Affected MCPs

Any remote MCP server reached via the mcp-remote bridge:

• Linear (https://mcp.linear.app/mcp)
• Anthropic / cloud-hosted MCPs
• Custom self-hosted remote MCPs (Streamable HTTP / SSE)

Local stdio MCPs (npx @modelcontextprotocol/server-X, uvx ...) that do not transitively depend on undici 7.x still work — that's why the breakage is invisible until users try a remote MCP.

Reproduction (60 seconds)

docker exec <your-anythingllm-container> sh -c \
  'npx -y mcp-remote https://mcp.linear.app/mcp'
# → crashes with the stacktrace above

Suggested fix

Update the NodeSource repository in docker/Dockerfile from node_18.x to node_20.x (or node_22.x LTS).

• Node 20.x is in LTS since Oct 2023.
• Node 18 reached End-of-Life on 2025-04-30.
• Node 22.x is LTS since Oct 2024.

This unblocks the entire remote-MCP feature surface in Docker with a one-line change.

Related

• [FEAT]: remote mcp server support for docker AnythingLLM #5051 (open) — "remote mcp server support for docker AnythingLLM". That request is actually a symptom of this root cause, not a separate feature: remote MCP via mcp-remote is already supposed to work, it just crashes immediately due to the Node version pin.

Environment

• Image: mintplexlabs/anythingllm:1.11.1 (also tested with v1.12.1)
• Host: Ubuntu / Docker, x86_64
• Node inside container: v18.20.8