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API Error: 400 Invalid request Error - Claude Code

Quick fix

Roll the Claude Code CLI or VSCode plugin back to an older version (2.1.150 or 145) and disable auto-update to resolve the 400.

Symptom

Section titled “Symptom”
Error output
API Error: 400 Invalid request Error

Cause

Section titled “Cause”

Specific Claude Code versions (2.1.69 and 152) changed or broke the request format — missing reasoning_content in thinking mode, or message body type validation failing — producing a 400 when going through the cc-switch proxy or calling a third-party API. Officially some of it was fixed in a later version (2.1.70), but for third-party API compatibility, rolling back and disabling auto-update is usually the way through.

Fix

Section titled “Fix”

  1. Run npm install -g @anthropic-ai/[email protected] to roll the Claude Code CLI back to 2.1.150 (or to 2.1.63).

  2. Disable auto-update in the config file so it does not upgrade itself again.

    // setting.json
    {
      "autoUpdates": false,
      "env": {
        "DISABLE_AUTOUPDATER": "1",
        "DISABLE_UPDATES": "1"
      }
    }

  3. If you use the VSCode plugin, roll the Claude Code plugin back to version 145 in extension management.

Affected Versions

Section titled “Affected Versions”
ToolClaude Code
Version2.1.69, 152
PlatformsWindows

Source Issues

Section titled “Source Issues”

This page is distilled from 2 real issues

FAQ

Section titled “FAQ”
Why does it still error after rolling back to 145?
Some users report 145 still having problems, which may depend on the specific model. One user noted no problems with models such as Max — try switching model or checking other configuration.
Is there an official fix for the 2.1.69 API format error?
Yes — it was fixed officially in v2.1.70. You can either upgrade to 2.1.70 or roll back to 2.1.63.
Section titled “Related problems”
401 Unauthorized: Incorrect API key providedAfter switching to OpenAI Official or turning the proxy off, clear the leftover third-party OPENAI_API_KEY from ~/.codex/auth.json and restart Codex.2 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.7 issues mergedSymlink target not found: .DirIcon broken symlink causes - CC SwitchAppImage install fails due to broken .DirIcon symlink. Fix by converting it to a relative path.2 issues merged

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