Cannot use Streamable HTTP MCP on Windows codex CLI (missing field command error)

Resolved 💬 9 comments Opened Sep 30, 2025 by bobobo-7 Closed Oct 6, 2025

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

What version of Codex is running?

codex-cli 0.42.0

Which model were you using?

gpt-5-codex

What platform is your computer?

windows11

What steps can reproduce the bug?

When trying to configure codex CLI to use a Streamable HTTP MCP server on Windows, I encounter a configuration loading error.
Config source: config.md example

experimental_use_rmcp_client = true
[mcp_servers.figma]
url = "http://127.0.0.1:3845/mcp"

When I start the codex CLI, Codex fails to load configuration with the following error:
Error loading configuration: missing field command in mcp_servers.figma

What is the expected behavior?

_No response_

What do you see instead?

_No response_

Additional information

_No response_

View original on GitHub ↗

9 Comments

realyn · 9 months ago

same question

ignatremizov · 9 months ago

Same here

experimental_use_rmcp_client = true
[mcp_servers.github]
url  = "https://api.githubcopilot.com/mcp/"
bearer_token = "ghp_ABC..."
startup_timeout_sec = 20
tool_timeout_sec = 90

$ codex
Error loading configuration: missing field `command`
in `mcp_servers.github`

zpv · 9 months ago

Y'all need to use the alpha builds of Codex. 0.42.0 does not have the experimental client.

npm install -g @openai/codex@0.43.0-alpha.10

r-sniper · 9 months ago

Y'all need to use the alpha builds of Codex. 0.42.0 does not have the experimental client. npm install -g @openai/codex@0.43.0-alpha.10

But its nowhere mentioned in doc, its only available in alpha release

https://github.com/openai/codex/blob/main/docs/config.md#streamable-http

r-sniper · 9 months ago

Also, I switched to >_ OpenAI Codex (v0.43.0-alpha.18)

Now the error goes away, but it says,

```/mcp

🔌 MCP Tools

• No MCP tools available.

jakeleventhal · 9 months ago

with 0.44.0 i still have issues
when i run /mcp it says

  • Server: figma
    • URL: http://127.0.0.1:3845/mcp
    • Tools: (none)

projects = { "/Users/jakeleventhal/Developer/rip-technologies" = { trust_level = "trusted" } }
model = "gpt-5-codex"
model_reasoning_effort = "high"

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

experimental_use_rmcp_client = true
[mcp_servers.figma]
url = "http://127.0.0.1:3845/mcp"

cant get it to work with the remote figma mcp either

hkfires · 9 months ago

with 0.44.0 i still have issues when i run /mcp it says `` • Server: figma • URL: http://127.0.0.1:3845/mcp • Tools: (none) `` projects = { "/Users/jakeleventhal/Developer/rip-technologies" = { trust_level = "trusted" } } model = "gpt-5-codex" model_reasoning_effort = "high" [mcp_servers.linear] command = "npx" args = ["-y", "mcp-remote", "https://mcp.linear.app/sse"] experimental_use_rmcp_client = true [mcp_servers.figma] url = "http://127.0.0.1:3845/mcp" cant get it to work with the remote figma mcp either

You should move the experimental_use_rmcp_client = true to the top level, for example

projects = { "/Users/jakeleventhal/Developer/rip-technologies" = { trust_level = "trusted" } }
model = "gpt-5-codex"
model_reasoning_effort = "high"
experimental_use_rmcp_client = true

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

[mcp_servers.figma]
url = "http://127.0.0.1:3845/mcp"

jakeleventhal · 9 months ago

great that worked @hkfires, now just waiting on the ability to auth (like with the remote figma MCP)

gpeal contributor · 9 months ago

0.45.0-alpha.6 now supports streamable http with oauth. Run codex mcp login figma with the alpa or wait for the final release which should be out in the next day or two.