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API Error: 422 format conversion error: Empty choices array Claude Code

Quick fix

The upstream NVIDIA NIM GLM-5.2 model intermittently returns an empty choices array. Turn on failover in cc-switch or retry the request.

Symptom

Section titled “Symptom”
Error output
API Error: 422 格式转换错误: Empty choices array
English translation

API Error: 422 format conversion error: Empty choices array

Cause

Section titled “Cause”

Calling the z-ai/glm-5.2 model through an upstream API such as NVIDIA NIM, the API occasionally returns a response carrying only usage statistics with choices as an empty array (particularly on large requests of 100-500KB, at roughly a 10-20% failure rate).

The cc-switch desktop build fixed this for the streaming case in v3.16.3, but the CLI build that Claude Code uses has not fully fixed that OpenAI format conversion logic, so parsing the empty array throws a 422 or a 502.

Fix

Section titled “Fix”

  1. Configure failover for the current model in cc-switch so an empty choices error falls back to another API interface automatically.

  2. Retry the request. The error is an intermittent upstream API problem, and resending usually succeeds.

Affected Versions

Section titled “Affected Versions”
ToolClaude Code
Version3.16.5 - 3.19.1 (affected range)
PlatformsmacOSWindows

Source Issues

Section titled “Source Issues”

This page is distilled from 2 real issues

FAQ

Section titled “FAQ”
Why does the desktop build not error while only Claude Code does?
The desktop build fixed the usage-only trailing packet with choices:[] in a streaming response in v3.16.3, but the CLI build Claude Code depends on has not picked up that conversion fix yet.
Is this error a cc-switch problem or an upstream API problem?
The root cause is the upstream API (NVIDIA NIM) returning an empty choices array that does not conform to the standard OpenAI format, but the cc-switch CLI build lacks tolerance for that malformed response.
Section titled “Related problems”
Claude Code Tool Call Failure via NVIDIA Proxy - CC Switch FixNVIDIA free-tier models are unstable; switch to stable providers like deepseek-ai/deepseek-v4-flash.2 issues merged401 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 merged

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