Codex CLI requests return HTTP 404 from /backend-api/codex/responses across versions and models

What version of Codex CLI is running?

codex-cli 0.150.0

What subscription do you have?

Plus

Which model were you using?

gpt-5.6-sol, gpt-5.6-terra, gpt-5.6-luna

What platform is your computer?

Linux fedora 7.1.12-100.fc43.x86_64 #1 SMP PREEMPT_DYNAMIC Fri Aug 28 14:08:18 UTC 2026 x86_64 GNU/Linux

What terminal emulator and version are you using (if applicable)?

No response

Codex doctor report

What issue are you seeing?

Thread ID: 01a067d5-2a38-7dd2-9820-38a54283f1ee

Codex CLI is currently unusable because requests to the ChatGPT Codex backend return HTTP 404.

Environment:

• Fedora Linux, x86_64
• ChatGPT Plus
• Codex CLI 0.150.0 and 0.153.0 both tested
• 0.153.0 was also downloaded directly from the official openai/codex GitHub release and executed independently

Models tested:

• gpt-5.6-sol
• gpt-5.6-terra
• gpt-5.6-luna

All tested models and both CLI versions reproduce the same failure.

Minimal reproduction:

1. Start Codex.
2. Submit a trivial read-only request such as:
   Read-only check only: run git status --short --branch and report the result. Do not modify anything.
3. Request fails with:
   unexpected status 404 Not Found: Unknown error, url: https://chatgpt.com/backend-api/codex/responses

WebSocket transport also fails:
Falling back from WebSockets to HTTPS transport. unexpected status 404 Not Found: Unknown error, url: wss://chatgpt.com/backend-api/codex/responses

Example Cloudflare Ray IDs:

• a355b42a3b2645f2-MIA
• a355b4575cf0c294-MIA
• a355b6438c4af372-MIA
• a355b6a6e98535b7-MIA

Additional potentially related symptoms:

• /status repeatedly reports:
  Limits: refresh requested; run /status again shortly.

• codex_apps MCP initialization fails with HTTP 404 during initialization.

• Codex 0.150.0 offered an update to 0.153.0 using:
  https://chatgpt.com/codex/install.sh

  That endpoint itself returns HTTP 404.

• The updater nevertheless reports:
  Update ran successfully! Please restart Codex.

• Direct verification:
  curl -I https://chatgpt.com/codex/install.sh
  returns HTTP/2 404.

• GitHub connectivity works normally. https://github.com/openai/codex/releases/latest redirects successfully to rust-v0.153.0, and the official 0.153.0 Linux x86_64 release downloaded successfully.

• Running that independently downloaded 0.153.0 binary reproduces the same /backend-api/codex/responses HTTP 404.

The failure therefore does not appear specific to:

• CLI 0.150.0
• a particular model
• the existing Codex thread/session
• the repository
• the local Codex installation

The problem appeared after an earlier Codex conversation was interrupted around usage/credit-window exhaustion. After the usage window should have refreshed, requests began returning these HTTP 404 responses.

Please investigate account/backend/CDN routing for the ChatGPT Codex endpoints, particularly /backend-api/codex/responses, and potentially /codex/install.sh.

The Codex /feedback command recorded feedback but reported (no logs) and directed me to create this GitHub issue and reference the thread ID above.

What steps can reproduce the bug?

Uploaded thread: 01a067d5-2a38-7dd2-9820-38a54283f1ee

What is the expected behavior?

No response

Additional information

No response

Start by reproducing the failure with the Codex CLI commands and the documented endpoints: /backend-api/codex/responses, its WebSocket form, /status, and /codex/install.sh. Compare CLI versions 0.150.0 and 0.153.0 and the independently downloaded release; done means identifying the cause of the 404 responses or documenting the backend routing issue with a verified expected response.