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CLAUDE_CODE_ATTRIBUTION_HEADER causes cache invalidation - CC Switch Fix

Quick fix

Set CLAUDE_CODE_ATTRIBUTION_HEADER=0 to disable the dynamic request header and restore KV cache hits.

Symptom

Section titled “Symptom”
Error output
缓存固定为13824
English translation

Cache is fixed at 13824

Cause

Section titled “Cause”

Starting from Claude Code v2.1.36, every API request includes an `x-anthropic-billing-header` with dynamic values such as cc_version and cc_entrypoint. These changing header values break KV cache prefix matching, forcing full prompt processing on every request. This increases latency and cost, and appears as cache counts not updating or staying fixed.

Many third-party proxies, such as LiteLLM and claude-code-router, do not recognize this header and may return ValidationException. Setting the environment variable `CLAUDE_CODE_ATTRIBUTION_HEADER=0` disables the header and restores normal cache behavior. Note: older Claude Code versions, such as v2.1.148, may have compatibility issues; update to the latest version, such as v2.1.215+.

Fix

Section titled “Fix”

  1. Add or set CLAUDE_CODE_ATTRIBUTION_HEADER to 0 in the system environment variables.

    Windows 用户可通过系统属性 -> 高级 -> 环境变量 设置
    # Linux/macOS 用户可在 ~/.bashrc, ~/.zshrc 或 /etc/environment 中添加:
    export CLAUDE_CODE_ATTRIBUTION_HEADER=0

Affected Versions

Section titled “Affected Versions”
ToolClaude Code
VersionUnknown
PlatformsWindowsmacOSLinux

Source Issues

Section titled “Source Issues”

This page is distilled from 1 real issues

FAQ

Section titled “FAQ”
Why is caching still broken after setting it?
Check whether your Claude Code version is too old, such as v2.1.148. Reports indicate older versions may have mutable-prefix compatibility issues. Update to v2.1.215 or later.
Does this setting affect the official Anthropic API?
No. It only disables the dynamic header used for billing and tracking and does not affect core functionality. If you use the official Anthropic API directly, this setting is usually unnecessary; it is useful with third-party proxies or local inference.
How can I quickly toggle this setting in CC Switch?
CC Switch does not currently provide a built-in toggle; Issue #2025 requests this feature. Set it manually in your operating system environment variables.
Section titled “Related problems”
ANTHROPIC_AUTH_TOKEN and ANTHROPIC_API_KEYRun `claude daemon stop --any` to kill leftover Claude background processes, then keep only one auth variable in `env` in `~/.claude/settings.json`.12 issues mergedANTHROPIC_AUTH_TOKEN and ANTHROPIC_API_KEYOpen `~/.claude/settings.json`, delete the duplicate auth variable so only the one your provider needs remains, save, and restart Claude Code.4 issues mergedAuth conflictLog out of the official Claude login, clear conflicting ANTHROPIC_* variables, set hasCompletedOnboarding to true in ~/.claude.json, and restart the terminal.6 issues merged

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