Codex returns 404 on /backend-api/codex/responses across all chats and multiple PCs, including brand-new chats (AKX)

What subscription do you have?

ChatGPT Pro

What platform is your computer?

Windows desktop. Reproduced on multiple computers using the same account.

What issue are you seeing?

Starting on 2026-09-03, every Codex prompt fails after repeated reconnect attempts:

Reconnecting 1/5
...
Reconnecting 5/5

unexpected status 404 Not Found: Unknown error,
url: https://chatgpt.com/backend-api/codex/responses

This is not limited to one conversation or one machine:

• Reproduces on multiple PCs.
• Reproduces in all existing Codex chats.
• Reproduces in a brand-new empty chat with a trivial prompt.
• Existing chats show red error/exclamation indicators after failed requests.
• Earlier in the same session, automatic remote compaction also failed with a 404, but the main blocker now is the regular /backend-api/codex/responses endpoint itself.

Observed Cloudflare Ray IDs:

a355911a9b813f34-AKX
a355911fecf4e4ca-AKX
a355938a0b43984c-AKX
a35597590fe58a3a-AKX
a3559ea0c806b7e6-AKX

Because the failure reproduces on multiple computers and in a completely new chat, it does not appear to be caused by conversation length, local project state, or a single corrupted thread.

What steps can reproduce the bug?

1. Open Codex Desktop.
2. Open any existing conversation, or create a brand-new empty conversation.
3. Send any prompt (even a trivial one).
4. Codex enters Reconnecting 1/5 through Reconnecting 5/5.
5. Request fails with 404 Not Found from https://chatgpt.com/backend-api/codex/responses.
6. Repeat on another computer with the same account: same result.

What is the expected behavior?

Codex should accept prompts and return responses normally in both existing and newly created chats.

Additional information

This appears to be part of the same current outage/regression as other reports filed today, including #42551, #42549, #42545, #42544, #42548 and #42546, but this report adds an AKX edge/region case and confirms the failure across multiple PCs and brand-new chats on a Pro account.

The only named entry point is the /backend-api/codex/responses endpoint; start by checking how this endpoint is reached and whether the related reports (#42551, #42549, #42545, #42544, #42548, and #42546) identify an owning component. Done means prompts succeed in existing and brand-new chats across the reported PCs instead of returning 404 after reconnect attempts.