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level "max" not supported, Codex Desktop

Quick fix

Select max for gpt-5.6-sol in Codex Desktop; ultra is not a separate reasoning effort.

Symptom

Section titled “Symptom”
Error output
CC Switch local proxy failed while handling Codex endpoint /responses.
Provider: <redacted>; model: gpt-5.6-sol;
upstream_status: HTTP 400;
cause: level "max" not supported, valid levels: low, medium, high, xhigh

Cause

Section titled “Cause”

In the report, Codex Desktop shows ultra on the native slider for gpt-5.6-sol, while a /responses request through the cc-switch local proxy returns level "max" not supported at the highest setting. The reporter suspected ultra may be mapped or normalized to max in the request path, but the original post provides no verifiable root-cause conclusion.

The maintainer explains that ultra is not a separate reasoning effort; it is max plus additional prompt injection. max is currently selectable, so there are no plans to implement ultra as a separate capability. This explains product semantics; it does not indicate that the proxy HTTP 400 in the original report was separately fixed.

Fix

Section titled “Fix”

  1. Select `max` for gpt-5.6-sol in Codex Desktop; do not configure `ultra` as a separate reasoning effort.

  2. If `max` does not produce the same behavior as `ultra`, reopen the source issue as requested by the maintainer and provide a comparison with the official model directory.

Affected Versions

Section titled “Affected Versions”
ToolCodex Desktop
Version26.707.x（报告环境，非确认受影响范围）
PlatformsWindows

Source Issues

Section titled “Source Issues”

This page is distilled from 1 real issues

FAQ

Section titled “FAQ”
Can I select max?
Yes. The maintainer states that `max` is currently selectable.
Is ultra a separate reasoning effort?
No. The maintainer states that `ultra` is `max` plus additional prompt injection and will not be implemented separately.
Section titled “Related problems”
unexpected status 404 Not FoundUpgrade cc-switch to v3.16.4+ and set the upstream format explicitly to Chat Completions on the Codex provider form.4 issues mergedapi failed deserialize json body intoDepending on the error: roll Claude Code back, upgrade cc-switch, turn the local proxy off, or stop sending unsupported fields.8 issues mergedInvalid schema for function — CodexUpgrade CC Switch to a version including the v3.18.0 fix for `parameters.type:null`; track the original issues for other `null` schema variants.13 issues merged

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