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Warmup request downgraded to model: gpt-5-mini - Claude Code

Quick fix

Turn the Copilot warmupDowngrade option off in CC Switch so requests are not silently replaced with gpt-5-mini.

Symptom

Section titled “Symptom”
Error output
[Copilot] Warmup request downgraded to model: gpt-5-mini

Cause

Section titled “Cause”

The CC Switch Copilot optimiser enables warmup downgrading by default (`warmup_downgrade: true`) with `gpt-5-mini` as the default replacement model. When the system classifies a sub-agent request as a warmup probe, it ignores the model you explicitly selected (`claude-opus-4.8-1m`, for example) and silently substitutes before the request reaches GitHub Copilot.

The cluster also holds other Copilot proxy anomalies: deeply indented code in a streaming response being misread as the "infinite whitespace bug" and the tool call discarded (#2646), and model mapping config not applying in proxy mode (#3231). Both stem from the proxy layer intervening too much or from logic defects, but this page addresses the model being downgraded unexpectedly.

Fix

Section titled “Fix”

  1. Edit the Copilot optimizer config by hand and set `warmupDowngrade` to `false` to disable the downgrade: `{"warmupDowngrade": false}`.

Affected Versions

Section titled “Affected Versions”
ToolClaude Code
Versioncc-switch 3.18.0
PlatformsmacOS

Source Issues

Section titled “Source Issues”

This page is distilled from 5 real issues

FAQ

Section titled “FAQ”
Why are main window requests fine while sub-agent requests get downgraded?
CC Switch classifies certain sub-agent requests as warmup probes, which triggers the default downgrade substitution. Main window requests are not classified that way.
Is a lost tool call from writing indented code through the Copilot proxy the same cause?
No. That comes from the infinite-whitespace detection threshold being too low (20) and catching legitimate output — a separate bug (#2646) that needs a cc-switch upgrade.
Section titled “Related problems”
EGL_BAD_PARAMETER white screen error - cc-switchInstall the native .deb or AUR package instead, or run the AppImage with LD_PRELOAD pointing at the system library, to resolve the ABI conflict.6 issues merged"event handler is re-entrant" error or startup crashUninstall Windows update KB5081263 or wait for cc-switch upgrade to avoid crashes and UI rendering failures caused by TAO EventLoop re-entry.2 issues mergedAtomic replace failed os error 50Change the Claude Code configuration directory from a WSL path back to a Windows local path, or roll back to v3.19.0.1 issues merged

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