MCP Transport error "SSE stream disconnected: AbortError: This operation was aborted"

[francescom-zenity]

What happened?

I configured a streamable-HTTP MCP server and I get continuous logs in LibreChat container

Version Information

I tried both v0.8.2 and v0.8.3-rc1

Steps to Reproduce

1. Add to your librechat.yaml a section like

mcpServers:
  test-mcp-server-local:
    type: "streamable-http"
    requiresOAuth: false
    url: http://10.211.55.3:7000/mcp
    timeout: 6000
    headers:
      X-User-ID: "{{LIBRECHAT_USER_ID}}"
      X-User-Email: "{{LIBRECHAT_USER_EMAIL}}"
      X-User-Role: "{{LIBRECHAT_USER_ROLE}}"
      Authorization: "Bearer YourSecretTokenHere"

2. Restart Librechat container

3. View Librechat logs

What browsers are you seeing the problem on?

No response

Relevant log output

2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] -------------------------------------------------┐
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] URL: http://10.211.55.3:7000/mcp
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] OAuth Required: false
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] Capabilities: {"experimental":{},"prompts":{"listChanged":true},"resources":{"subscribe":false,"listChanged":true},"tools":{"listChanged":true}}
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] Tools: get_current_weather, get_forecast
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] Server Instructions: undefined
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] Initialized in: 149ms
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] -------------------------------------------------┘
2026-02-18 05:17:16 error: [MCP][test-mcp-server-local] Transport error (may require manual intervention): SSE stream disconnected: AbortError: This operation was aborted
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] Reconnecting 1/3 (delay: 2000ms)
2026-02-18 05:17:16 error: [MCP][test-mcp-server-local] Transport error (may require manual intervention): SSE stream disconnected: AbortError: This operation was aborted
2026-02-18 05:17:18 info: [MCP][test-mcp-server-local] Creating streamable-http transport: http://10.211.55.3:7000/mcp
2026-02-18 05:17:24 error: [MCP][test-mcp-server-local] Transport error (may require manual intervention): SSE stream disconnected: TypeError: terminated
[... same messages repeated forever every 2sec ...]

Screenshots

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[francescom-zenity]

A couple more notes: the MCP server is actually a test project I created here: https://github.com/f18m/test-mcp-server
It was originally using the FastMCP Python library v1.26.0 from modelcontextprotocol.io (and LibreChat was emitting the same errors).
I then decided to switch over to the FastMCP 3.0.0 from https://gofastmcp.com/, but the problem persists.

[francescom-zenity]

Also note that on the MCP server side, I only see successful requests coming from LibreChat:

INFO:     172.18.0.1:49714 - "GET /mcp HTTP/1.1" 200 OK
INFO:     172.18.0.1:49720 - "POST /mcp HTTP/1.1" 200 OK
INFO:     172.18.0.1:49742 - "POST /mcp HTTP/1.1" 202 Accepted
INFO:     172.18.0.1:49758 - "GET /mcp HTTP/1.1" 200 OK

[alexhermida]

Any additional info on this? It's happening to me testing the new v0.8.3-rc1, I can only see the errors during LibreChat startup, testing Librechat and the tools everything seems to work fine.

thanks!

[francescom-zenity]

hey @alexhermida ,
if you check the logs of Librechat you don't see continuous (every 2 sec) streams of errors like

2026-02-18 05:17:16 error: [MCP][test-mcp-server-local] Transport error (may require manual intervention): SSE stream disconnected: AbortError: This operation was aborted
2026-02-18 05:17:16 info: [MCP][test-mcp-server-local] Reconnecting 1/3 (delay: 2000ms)
2026-02-18 05:17:16 error: [MCP][test-mcp-server-local] Transport error (may require manual intervention): SSE stream disconnected: AbortError: This operation was aborted
2026-02-18 05:17:18 info: [MCP][test-mcp-server-local] Creating streamable-http transport: http://10.211.55.3:7000/mcp
2026-02-18 05:17:24 error: [MCP][test-mcp-server-local] Transport error (may require manual intervention): SSE stream disconnected: TypeError: terminated
[... same messages repeated forever every 2sec ...]

?

[alexhermida]

Hi @francescom-zenity not in my case, I have the error just during LibreChat startup (v0.8.3-rc1). I'm using a custom header for authorization like X-API-Key: "my-key" and requiresOAuth: false

I assume you also setup for your domain/ip-address:

mcpSettings:
  allowedDomains:

[danny-avila]

Should be resolved here: #11936

[alexhermida]

Thanks @danny-avila ! 🙏🏽

[francescom-zenity]

Thanks @danny-avila I just tested the latest -dev build and I confirm the bug is fixed!