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Unexpected status 503 Service Unavailable: Codex

Quick fix

When using v2ray, configure its routing to bypass LAN and mainland China domains, then access through CC Switch local routing again.

Symptom

Section titled “Symptom”
Error output
Unexpected status 503 Service Unavailable: Unknown error, url: http://127.0.0.1:15721/v1/responses

Cause

Section titled “Cause”

In closed issue #3673, Codex returned 503 when accessing DeepSeek through CC Switch local routing. The reporter confirmed that v2ray routing caused the problem; bypassing LAN and mainland China domains resolved it.

Open issue #6315 reports the same local `/v1/responses` 503 with NVIDIA NIM and custom models, but no fix has been confirmed. The same thread also contains an upstream HTTP 404 variant, so this case may not have the same root cause as v2ray.

Fix

Section titled “Fix”

  1. If you are using v2ray, open its routing settings.

  2. Configure v2ray routing to bypass LAN and mainland China domains.

  3. Run Codex again through CC Switch local routing and check whether the 503 disappears.

  4. If it still fails with NVIDIA NIM, check whether the error has changed to an upstream HTTP 404. No confirmed solution for this variant exists in the current issue.

Affected Versions

Section titled “Affected Versions”
ToolCodex
Version受影响：3.16.1 - 3.19.2
PlatformsmacOSWindows

Source Issues

Section titled “Source Issues”

This page is distilled from 2 real issues

FAQ

Section titled “FAQ”
Why does curl work with v2ray enabled while Codex returns 503?
The reporter in issue #3673 confirmed that v2ray routing settings caused the problem. Configuring the route to bypass LAN and mainland China domains resolved it.
Why can Codex still not connect after configuring the NVIDIA API and local routing?
Issue #6315 has no confirmed answer yet. The thread contains both 503 and upstream HTTP 404 errors; the latter also includes specific Provider and model information, so it may have a different cause.
What should I do if the model name appears as custom and cannot be switched?
Issue #6315 reports this behavior, but the current thread provides no confirmed fix.
Section titled “Related problems”
maximum context length is 1048565 tokens.Reduce PDF or message input. If the DeepSeek-compatible endpoint does not support PDF, stop uploading it, update CC Switch, and retry.1 issues mergedCodex auth.json overwritten, KEY mix-up, or official login lostUpgrade cc-switch to the latest version (v3.16.1 fixes the v3.16.0 KEY mix-up regression; v3.20.1/4.0 fix logout overwriting auth.json and losing… (Codex)30 issues mergedModel list is empty; Codex cannot select the DeepSeek modelUpgrade to CC Switch 4.0 and reapply the DeepSeek preset; model list display in the Codex desktop app also depends on its version support.5 issues merged

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