MCP connection failing with the (supposedly) newly-supported SSE process #5634

What version of Codex is running?

0.48.0

What subscription do you have?

API

Which model were you using?

gpt-5-codex high

What platform is your computer?

Windows 11

What issue are you seeing?

The connection is giving me a 404 error after a successful OAUTH login.

in my config.toml file:

[mcp_servers.atlassian]
url = "https://mcp.atlassian.com/v1/sse"

I also have experimental_use_rmcp_client = true enabled, as if I disable this it doesn't even let me login.

Then when I try and run the login flow:

PS H:\Projects\Ark Backup\dev> codex mcp login atlassian

Authorize atlassian by opening this URL in your browser:
https://mcp.atlassian.com/v1/authorize?...

Successfully logged in to MCP server 'atlassian'.

PS H:\Projects\Ark Backup\dev> codex
╭────────────────────────────────────────────────╮
│ >_ OpenAI Codex (v0.48.0) │
│ │
│ model: gpt-5-codex high /model to change │
│ directory: H:\Projects\Ark Backup\dev │
╰────────────────────────────────────────────────╯

To get started, describe a task or try one of these commands:

/init - create an AGENTS.md file with instructions for Codex
/status - show current session configuration
/approvals - choose what Codex can do without approval
/model - choose what model and reasoning effort to use
/review - review any changes and find issues

■ MCP client for atlassian failed to start: handshaking with MCP server failed: Send message error Transport
[rmcp::transport::worker::WorkerTransport<rmcp::transport::streamable_http_client::StreamableHttpClientWorker<rmcp::transport::auth::AuthClient<reqwest::asy
nc_impl::client::Client>>>] error: Client error: HTTP status client error (404 Not Found) for url (https://mcp.atlassian.com/v1/sse), when send initialize
request

What steps can reproduce the bug?

Connect to the Atlassian (or any other SSE protocol MCP server, although I have not checked others). It will let you login, the web page pops up to give consent, and then returns you to the CLI window successfully. Then starting codex will give an error immediately.

What is the expected behavior?

It logs in and connects successfully

Additional information

No response