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gpt-5.3-codex fails with 404 when authenticated via OpenAI API key #12839
Description
Description
When a user authenticates with a standard OpenAI API key via opencode auth login → "Manually enter API Key", gpt-5.3-codex appears as an available model but fails with a 404 error at runtime.
Root Cause
gpt-5.3-codex is only available via the ChatGPT Codex endpoint (chatgpt.com/backend-api/codex/responses), which requires OAuth authentication. It is not listed on the OpenAI API platform.
The codex plugin (src/plugin/codex.ts) rewrites the request URL to the ChatGPT endpoint for OAuth users, but for API key users it returns early without any filtering:
if (auth.type !== "oauth") return {}
This means gpt-5.3-codex (from models.dev) remains in the available model list, but requests go to api.openai.com/v1/responses where the model does not exist → 404.
Note: Other codex models like gpt-5.2-codex are available on the OpenAI API platform and work correctly with API keys.
Steps to Reproduce
- Run opencode auth login
- Select OpenAI → "Manually enter API Key"
- Enter a valid OpenAI API key
- Select gpt-5.3-codex as the model
- Send a message → 404 error
Expected Behavior
gpt-5.3-codex should not appear as available for API key users, or a clear error should explain that OAuth is required.
Activity
github-actions commentedon Feb 9, 2026
I've searched for potential duplicates and found several related GPT-5.3-Codex issues, but no exact duplicates:
Related (but different issues):
This issue appears to be unique regarding the authentication-based availability filtering and 404 error when using API keys with GPT-5.3-Codex.
github-actions commentedon Feb 9, 2026
No exact duplicates found. This issue appears to be unique regarding the authentication-based model availability filtering for GPT-5.3-Codex with API keys.
fix: filter gpt-5.3-codex from API key users
R44VC0RP commentedon Feb 9, 2026
Confirmed — gpt-5.3-codex is OAuth-only and shouldn't be visible for API key users.
Your PR #12837 looks good, filtering it out for non-OAuth users is the right fix. We'll review and merge it.
For now, if you're using an API key, stick with gpt-5.2-codex or other models that are available on the OpenAI API platform.
iyoda commentedon Feb 15, 2026
Thanks for the confirmation! Sounds good — using gpt-5.2-codex for now.
felixzieger commentedon Feb 25, 2026
The model is available via API now and works with opencode.
jomach commentedon Feb 27, 2026
install opencode -> /connect -> Github Copilot -> /models -> GPT-5.2-Codex