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api failed deserialize json body into cc-switch

Quick fix

Depending on the error: roll Claude Code back, upgrade cc-switch, turn the local proxy off, or stop sending unsupported fields.

Symptom

Section titled “Symptom”
Error output
API Error: 400 Failed to deserialize the JSON body into the target type: messages[1].role: unknown variant `system`, expected `user` or `assistant` at line 1 column 4371

Cause

Section titled “Cause”

This error means the upstream model API rejected the JSON request body that cc-switch forwarded or the client generated. The issues hold several variants. Claude Code 2.1.154 puts the system prompt into the messages array with role: "system", while the DeepSeek /anthropic endpoint requires system as a top-level field. When Codex /responses is converted to Chat Completions through cc-switch, a tool call can lose its name field — fixed in cc-switch 3.16.4. A non-multimodal DeepSeek model receiving image_url / image content produces the same class of 400. And users found that turning the cc-switch local proxy on or off changes compatibility for some models.

Fix

Section titled “Fix”

  1. If the error contains messages[1].role: unknown variant `system`, roll Claude Code back to 2.1.153 or 2.1.152 and turn auto-update off.

  2. If the error contains missing field `name`, upgrade cc-switch to 3.16.4 or newer — it is still present in 3.16.3.

  3. If the error contains unknown variant `image_url`, unknown variant `image`, or a similar multimodal field, stop sending images to non-multimodal models such as DeepSeek.

  4. If some models work and others 400 while switching between them, try turning the local proxy on the cc-switch home screen off and on again. Maintainers explain some providers are more compatible with the local proxy on, and others more stable with it off.

  5. If the DeepSeek official API previously reported a system / developer role problem, maintainers report DeepSeek fixed it upstream — retry first, and only fall back to rolling Claude Code back if it still fails.

Affected Versions

Section titled “Affected Versions”
ToolClaude Code / Codex
VersionUnknown
PlatformsmacOSWindows

Source Issues

Section titled “Source Issues”

This page is distilled from 7 real issues

FAQ

Section titled “FAQ”
Which Claude Code version should I roll back to?
Several users confirm npm i -g @anthropic-ai/[email protected] works, and others solved it by rolling back to 2.1.152. Turn Claude Code auto-update off afterwards.
Does the VS Code Claude Code plugin need rolling back too?
If you use the VS Code plugin, uninstall the current one and reinstall version 2.1.153.
Why does DeepSeek work once I turn the cc-switch local proxy off?
Providers differ in how they handle Anthropic-specific fields and proxy conversion. Maintainers suggest some models do better with the local proxy and Claude takeover on, while others are more stable with the local proxy off.
Why can DeepSeek not accept images?
Maintainers and users in the issues confirm models such as DeepSeek V3.2 are not multimodal and do not support image / image_url content, so sending an image triggers the deserialize 400.
Is missing field `name` a model problem or a cc-switch problem?
It relates to a tool call losing its name when Codex /responses is converted to Chat Completions. Maintainers confirmed cc-switch 3.16.3 is affected and 3.16.4 fixed it.
Section titled “Related problems”
Request body format invalid error - Claude CodeUpgrade cc-switch and enable the Rectifier, or add MAX_THINKING_TOKENS=0, for compatibility with third-party API formats.4 issues mergedConsole Go: Upstream request failedThis 400 comes from the OpenCode Go gateway rejecting an incompatible payload. Restart the proxy to restore session mapping, or avoid WebSearch and images.3 issues mergedDeepSeek prefix cache hit rate drop - CC Switch fixUpgrade to cc-switch v3.16.3 to fix cache hit rate calculation errors caused by format conversion.2 issues merged

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