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The 'deepseek-v4-flash' model is not supported - Codex

Quick fix

Enable the keep-official-login option in cc-switch, confirm local route takeover is on, then restart Codex desktop.

Symptom

Section titled “Symptom”
Error output
The 'deepseek-v4-flash' model is not supported when using Codex with a ChatGPT account.

Cause

Section titled “Cause”

Codex desktop (the upstream client) has a limitation: its model picker decides whether to show third-party custom models based on whether you signed in with an official ChatGPT identity. Without that identity it forcibly reverts to the official default model and blocks third-party model requests. Early versions may also have had endpoint format compatibility problems, though newer cc-switch supports the format conversion.

Fix

Section titled “Fix”

  1. Sign in to an official ChatGPT account once in Codex desktop, so official credentials are stored in ~/.codex/auth.json.

  2. In cc-switch settings, enable "Keep official login when switching third-party providers".

  3. Make sure local route-takeover is enabled for the third-party provider you use.

  4. Quit Codex desktop completely, restart it, and open the model picker.

Affected Versions

Section titled “Affected Versions”
ToolCodex
VersionUnknown
PlatformsWindowsmacOS

Source Issues

Section titled “Source Issues”

This page is distilled from 3 real issues

FAQ

Section titled “FAQ”
Why does the model disappear again after a while?
The preserved official credentials may have expired. Sign in to an official ChatGPT account once more in Codex to restore it.
I can see third-party models in the terminal but not in the desktop app. What now?
That means the data layer is fine and it is purely a desktop UI limitation. Sign in to the official account in the desktop app and enable the cc-switch keep-login option as described.
Can I sign in to Codex with a DeepSeek API directly?
Yes — users report signing in to Codex with a DeepSeek API directly works fine. But to relay through cc-switch, follow the steps above to preserve the official login state.
Section titled “Related problems”
CC Switch local proxy failed while handlingUpgrade CC Switch to the latest version and start a new Codex conversation; invalid schema or image blocks left in old session history will keep triggering 400.43 issues mergedAbsolutePathBuf deserialized without a base pathOn Codex for macOS, relative paths written by cc-switch cause this error. Change `model_catalog_json` in `~/.codex/config.toml` to an absolute path.2 issues mergedCodex provider API keys overwrite each other after a restart or switchEnable CC Switch local proxy takeover, or use experimental_bearer_token in config.toml, to bypass the auth.json sync defect.7 issues merged

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