[Bug]: Codex Desktop does not expose MCP tools from MCP for Unity HTTP server on Windows 11

[AmberY1618]

What happened?

I am using MCP for Unity with Codex Desktop on Windows. The Unity MCP server starts correctly and responds at http://127.0.0.1:8080/mcp, but Codex Desktop does not expose any Unity MCP tools when I configure it directly as an HTTP MCP server.

Environment:

• OS: Windows
• Machine: Lenovo Windows PC
• Unity version: 2022.3.44f1 (c3ae09b9f03c)
• MCP for Unity server package: mcpforunityserver==9.7.1
• Unity MCP URL: http://127.0.0.1:8080/mcp
• Codex Desktop version: 26.602.40724
• Codex config has rmcp_client = true
• Windows sandbox setting: elevated

Original Codex MCP config:

[mcp_servers.unityMCP]
url = "http://127.0.0.1:8080/mcp"

The Unity MCP server appears healthy. A direct request to the endpoint returns a protocol-level response, not a connection failure:

  "jsonrpc": "2.0",
  "id": "server-error",
  "error": {
    "code": -32600,
    "message": "Not Acceptable: Client must accept text/event-stream"}

However, after restarting Codex Desktop, no Unity MCP tools are exposed. Tools such as read_console, manage_gameobject, find_gameobjects, and manage_scene are not available.

As a workaround, I created a local stdio bridge using the Python MCP SDK. The bridge connects to the same Unity MCP HTTP endpoint using streamable_http_client. Through that stdio bridge, Codex can see the Unity MCP server correctly. The bridge reports:

43 tools
19 resources
6 resource templates
Calling read_console through the stdio bridge succeeds and returns Unity console logs.

So the Unity MCP server itself seems to work. The issue appears to be that Codex Desktop does not expose the tools when connecting directly to the Unity MCP HTTP/streamable endpoint.

Reproduction steps

1.Open the Unity project on Windows.

2.Start MCP for Unity from inside Unity.

3.Confirm that Unity reports the MCP server is running at:
http://127.0.0.1:8080/mcp

4.Open Codex Desktop.

5.Configure Codex to use the Unity MCP server directly:

[mcp_servers.unityMCP]
url = "http://127.0.0.1:8080/mcp"

6.Make sure remote MCP support is enabled:

[features]
rmcp_client = true

7.Restart Codex Desktop.

8.Ask Codex to detect or use the Unity MCP server.

9.Observe that Codex fails to detect/connect to the Unity MCP server and does not expose any Unity MCP tools.

10.Expected result: Codex should expose Unity MCP tools such as read_console, find_gameobjects, manage_gameobject, and manage_scene.

11.Actual result: Codex does not expose any Unity MCP tools when using the direct HTTP MCP config.

Unity version

2022.3.44f1

MCP for Unity package version

9.7.1

Python server version

No response

MCP client

Codex

Transport

HTTP (default)

OS

Windows

Relevant logs / console output

Checks

• I searched existing issues and did not find a duplicate
• I included logs / steps to reproduce

[BBigBei]

Same here

[DDLC-theyzs]

same here, and thank you for your temporal solution, works for me