Custom MCP with Streamable HTTP is completely broken

[emi-dm]

Describe the bug

When I try to connect my MCP with cagent and DMR model (gpt-oss), the CLI stopped.

Version affected

Latest version of cagent released for MacOS

How To Reproduce

Detailed steps to reproduce the behavior:

1. Create agent.yml file :

version: "2"

agents:
  root:
    model: local-oai
    description: Un asistente útil para la investigación científica
    instruction: |
      Eres un asistente amistoso que ayuda en investigación científica.
    toolsets:
      - type: mcp
        ref: docker:duckduckgo # stdio transport
      - type: mcp # Model Context Protocol
        remote:
          url: "https://google-scholar-mcp-main.onrender.com/mcp" # Base URL to connect to
          transport_type: "streamable" # Type of MCP transport (sse or streamable

models:
  local-oai:
    provider: dmr
    model: ai/gpt-oss:latest
    max_tokens: 64000

2. Run cagent agent.yml and type "Hola"

Expectation

The model call the MCP functions.

OS and Terminal type

MacOS

[rumpl]

@emi-dm is the “fetch_content” tool from the streamable server or duckduckgo?

[emi-dm]

Hi @rumpl ! I think that the problem is related to the use of custom MCP server. I think it because I tried it without duckduckgo mcp (screenshot is attached)!

The custom MCP is implemented with fastmcp and it works with other MCP clients such as VSCode or Cursor.

[krissetto]

Should work now! Tested with gpt-oss and qwen3 models on DMR

[emi-dm]

Wow, thank you so much for the quick response and patch @krissetto @rumpl Do you have any group or chat to talk about cagent or docker ai updates?

[rumpl]

Find us on slack :)

https://github.com/docker/cagent?tab=readme-ov-file#share-your-feedback

[emi-dm]

I can't join without @docker mail :(

[rumpl]

Hm… We’ll fix the link. In the meantime, there is a link to the docker’s community slack on this page: https://www.docker.com/support/

Find us in the #cagent channel