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thinking enabled but reasoning_content missing Claude Code

Quick fix

Disable Thinking mode in Claude Code, or upgrade cc-switch to fix Kimi/Moonshot tool call errors.

Symptom

Section titled “Symptom”
Error output
API Error: 400 {"error":{"message":"thinking is enabled but reasoning_content is missing in assistant tool call message at index 2","type":"invalid_request_error"}}

Cause

Section titled “Cause”

When using models like Kimi/Moonshot via Silicon Flow with Claude Code for multi-turn conversations involving tool calls, cc-switch discards the thinking block during Anthropic-to-OpenAI format conversion. Providers like Moonshot require the reasoning_content field in assistant tool call messages when thinking is enabled; its absence triggers an HTTP 400 error. This issue is fixed in cc-switch by injecting reasoning_content (defaulting to "tool call") for Kimi/Moonshot paths.

Fix

Section titled “Fix”

  1. Upgrade cc-switch to version 3.14.2 or later. This version fixes the missing reasoning_content issue for Kimi/Moonshot paths by automatically injecting the field or using a placeholder.

  2. If upgrading is not immediately possible, disable Thinking mode in the Claude Code interface as a temporary workaround to avoid triggering this API validation.

Affected Versions

Section titled “Affected Versions”
ToolClaude Code
Versionpre-3.14.2
PlatformsWindowsmacOSLinux

Source Issues

Section titled “Source Issues”

This page is distilled from 2 real issues

FAQ

Section titled “FAQ”
Why does this error only occur during tool calls?
The error occurs during multi-turn conversations. After the model generates thinking and tool_use, Claude Code sends the history back upstream. The conversion logic loses the thinking content, causing assistant messages containing tool_calls to lack the required reasoning_content.
Will the fix affect other OpenAI-compatible models?
No. The fix restricts reasoning_content injection to the Kimi/Moonshot path (determined by model name or base_url), preventing unknown field pollution on generic OpenAI-compatible backends.
Why do models hosted on Silicon Flow also report this error?
Models hosted on platforms like Silicon Flow (e.g., Kimi) follow the same API specification. When Thinking mode is enabled and multi-turn tool calls occur, a request body lacking reasoning_content triggers a 400 error.
Section titled “Related problems”
Third-party model still claims based on GPT-5 - CodexMove the `baseInstructions` override out of the `if profile != ProxyChat` block so it applies to ProxyChat. Currently it is not injected even when set.1 issues mergedcontent[].thinking must be passed backUpgrade cc-switch to v3.16.0 or newer. As a stopgap, roll Claude Code back to 2.1.150 or turn thinking off.11 issues mergedBody text appears in thinking blocks, visible text nearly emptyUpgrade cc-switch to a build with PR #4210. Reactive thinking-placeholder handling fixes long-context freezes and body-text collapse.1 issues merged

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