Codex CLI: gpt-5.5 returns 404 on first message (Brazil/GIG region)

Resolved 💬 12 comments Opened Jun 7, 2026 by arkmetal98 Closed Jun 12, 2026

💡 Likely answer: A maintainer (github-actions[bot], contributor) responded on this thread — see the highlighted reply below.

Bug Report: gpt-5.5 returns 404 on Codex CLI (Brazil region)
Environment
Codex CLI version: 0.137.0
OS: Windows 11 Home Single Language
PowerShell: 5.1.26100.8457
Region: Brazil (timezone: E. South America Standard Time)
Account type: ChatGPT Plus/Pro (OAuth login)
Expected Behavior
codex --model gpt-5.5 should work the same as gpt-5.4, since gpt-5.5 is already available in the ChatGPT web interface for the same account.
Actual Behavior
Codex CLI initializes successfully with gpt-5.5 xhigh, but the first message triggers a 404:
\
unexpected status 404 Not Found: Model not found gpt-5.5-codex-1p-exp-p-0604-811f2f-ev3-text-control
url: https://chatgpt.com/backend-api/codex/responses
cf-ray: a082c44deb241fa0-GIG
request id: 308fe07b-0020-4d3d-93f9-9eeb9d9957fb
\\
Steps to Reproduce
Run codex --model gpt-5.5
Type any message (e.g., hello)
Observe 404 error before any response is generated
Additional Evidence
gpt-5.4 works perfectly on the same CLI installation
ChatGPT web interface has full access to gpt-5.5 with the same account
Endpoint https://chatgpt.com/backend-api/codex/responses responds to OPTIONS (405) — endpoint is online
CF-Ray suffix GIG indicates Cloudflare datacenter in Brazil (Galeão/RJ)
No OPENAI_* environment variables interfering
Hypothesis
The model gpt-5.5-codex-1p-exp-p-0604-811f2f-ev3-text-control has not been propagated to the Codex backend serving the GIG (Brazil) region, while the ChatGPT web frontend already has it.
Workaround
Use gpt-5.4 in Codex CLI until the rollout reaches the GIG datacenter.

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12 Comments

github-actions[bot] contributor · 1 month ago

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

#26910
#26892
#26902

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arkmetal98 · 1 month ago

I checked the potential duplicates (#26910, #26892, #26902). All report the same 404, but in different regions (MAA = India, NRT = Japan). My issue adds the GIG (Brazil) datacenter to the pattern. This confirms it's a global rollout desync across multiple Cloudflare regions, not an isolated account issue.

ax-openai · 1 month ago

Hi everyone! Sorry, we are looking into this. Will report back here shortly.

ntrjusti · 1 month ago

I'm having the same problem with the Codex extension for VS Code.
unexpected status 404 Not Found: Model not found gpt-5.5, url: https://chatgpt.com/backend-api/codex/responses, cf-ray: a08a99e57aa564a9-GIG, request id: 9cbe45b3-2e44-4758-8bd4-efb36682f8da

ax-openai · 1 month ago

Thanks for your patience. The backend issue causing gpt-5.5 requests to return 404 Model not found is now resolved.

Please try again. If it still fails, share a fresh request ID and timestamp.

ntrjusti · 1 month ago

Thanks for the feedback, it worked after your corrections.

On Tue, Jun 9, 2026 at 6:24 PM Ax @.***> wrote:

ax-openai left a comment (openai/codex#26916) <https://github.com/openai/codex/issues/26916#issuecomment-4664629185> Thanks for your patience. The backend issue causing gpt-5.5 requests to return 404 Model not found is now resolved. Please try again. If it still fails, share a fresh request ID and timestamp. — Reply to this email directly, view it on GitHub <https://github.com/openai/codex/issues/26916?email_source=notifications&email_token=CEZGI5SMBHBXZDSZA4X5V7L47CFCJA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINRWGQ3DEOJRHA22M4TFMFZW63VHMNXW23LFNZ2KKZLWMVXHJLDGN5XXIZLSL5RWY2LDNM#issuecomment-4664629185>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/CEZGI5RMJ26UN6OBGFBP7LL47CFCJAVCNFSM6AAAAACZ6HJBUWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DMNRUGYZDSMJYGU> . Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/CEZGI5VVC5VF3DOPA5R2DOD47CFCJA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINRWGQ3DEOJRHA22M4TFMFZW63VHMNXW23LFNZ2KKZLWMVXHJKTGN5XXIZLSL5UW64Y> and Android <https://github.com/notifications/mobile/android/CEZGI5RZQJJPIUI44BW5ZB347CFCJA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINRWGQ3DEOJRHA22M4TFMFZW63VHMNXW23LFNZ2KKZLWMVXHJLTGN5XXIZLSL5QW4ZDSN5UWI>. Download it today! You are receiving this because you commented.Message ID: @.***>

ax-openai · 1 month ago

Closing as resolved. If this recurs, please open a new issue with a fresh request ID and timestamp.

ccaiolopes · 1 month ago

unexpected status 404 Not Found: Unknown error, url: https://chatgpt.com/backend-api/codex/responses, cf-ray: a0d3a9cb6f67a46c-GRU

BuenoSintax · 1 month ago

me too unexpected status 404 Not Found: Unknown error, url: https://chatgpt.com/backend-api/codex/responses, cf-ray: a0d3ac802f87e1ab-GRU

tc-rmachado · 1 month ago

unexpected status 404 Not Found: Unknown error, url: https://chatgpt.com/backend-api/codex/responses, cf-ray: a0d3b0792aefad09-GRU

carubbi · 1 month ago

unexpected status 404 Not Found: Unknown error, url: https://chatgpt.com/backend-api/codex/responses, cf-ray: a0d3b540582f480d-GRU

juanvmerces-dev · 27 days ago

Closing as resolved. If this recurs, please open a new issue with a fresh request ID and timestamp.

unexpected status 404 Not Found: Model not found gpt-5.5, url: https://chatgpt.com/backend-api/codex/responses, cf-ray: a103ba488a3c125c-GIG