SSE based MCP servers are non-configurable

Resolved 💬 7 comments Opened Aug 14, 2025 by Shaurya-Sethi Closed Sep 3, 2025

💡 Likely answer: A maintainer (cpjet64, contributor) responded on this thread — see the highlighted reply below.

What version of Codex is running?

0.19.0

Which model were you using?

What platform is your computer?

Linux 6.6.87.2-microsoft-standard-WSL2 x86_64 x86_64

What steps can reproduce the bug?

On trying to add a new MCP server to config.toml inside the .codex folder as instructed in the documentation, codex is unable to recognize the MCP server and shows the following log when starting up:
MCP client for zep-docs failed to start: No such file or directory (os error 2)

This only happens for servers like zep that make use of sse as their transport and have url but no commands or args like stdio or http servers that run via npm/npx/docker, etc.

What is the expected behavior?

Codex, like any other coding agent (Claude, copilot, etc) should be able to recognize SSE based mcp servers when configured in config.toml

What do you see instead?

Additional information

This same server works when added to gemini-cli, copilot, and cline.

View original on GitHub ↗

7 Comments

nerdneilsfield · 11 months ago

I have a relative issue, when I use the http MCP, it doesnt work!

[mcp_servers.grep]
type = "http"
url = "https://mcp.grep.app"

When I start codex, it shows:

Δ codex
Error loading configuration: missing field `command`
in `mcp_servers.grep`

aysuio · 11 months ago

same issue. Does anyone have workaround currently? I see some repo having local mcp, but not sure if they are trustworthy

wiiiimm · 11 months ago

According to https://github.com/openai/codex/blob/main/codex-rs/config.md#mcp_servers, only local servers

Defines the list of MCP servers that Codex can consult for tool use. Currently, only servers that are launched by executing a program that communicate over stdio are supported. For servers that use the SSE transport, consider an adapter like mcp-proxy.

@aysuio Hopefully, they will support HTTP and SSE soon, till then, you can try mcp-proxy and mcm-remote might be a good workaround.

UPDATE:
During my research, I stumbled upon Docker MCP Toolkit. It allows you to run lots of remote MCP as through their local docker cli -> docker (docker mcp gateway run) -> mcp servers.

# ~/.codex/config.toml

[mcp_servers.MCP_DOCKER]
command = "docker"
args    = ["mcp", "gateway", "run"]
type    = "stdio"


[mcp_servers.linear-mcp]
type    = "stdio"
command = "npx"
args    = ["-y", "mcp-remote", "https://mcp.linear.app/sse"]

With Docker's MCP Toolkit and mcp-remote, I am able to call the GitHub and Linear via MCP:

cpjet64 contributor · 10 months ago

@wiiiimm I have been using Docker MCP with Claude Code for a hot minute now but have never been able to get it to work with Codex. I have tried every method different AI have suggested and just tried the method you showed as well but still nothing. What version of Codex are you running? I am on 23 and am starting to think it might be a bug.

MCP client for MCP_DOCKER failed to start: request timed out

Artein · 10 months ago

@Shaurya-Sethi, here is how Codex added Attlasian as mcp. Hope it helps

/.codex/config.toml:

[mcp_servers.atlassian]
command = "npx"
args = ["-y", "mcp-remote", "https://mcp.atlassian.com/v1/sse"]
env = { }

25May2025 · 10 months ago

In commit:
https://github.com/openai/codex/commit/014562eef0ec1a496951c5a8d6b08e2de9fb59d7
it is added:
"feat: enable Streamable HTTP MCP servers & lazy loading of tools"
by an OpenAI dev
so it seems like it will be soon supported naturally

Edit 9/11/2025 the pull request was closed without being merged

gpeal contributor · 10 months ago

Duplicate of #2129