Claude Code Sends Prompt-Caching Beta Header to Custom Endpoints Even When Disabled

What this error means

API error 400: The provider does not support the prompt-caching-scope-2026-01-05 beta header is a Claude Code failure pattern reported for developers trying to fix claude code sending prompt-caching beta header to custom api endpoints (anthropic_base_url) when caching is disabled. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub issue #21644 in anthropics/claude-code: With enablePromptCaching=false and useAnthropicBetaHeaders=false set in VS Code settings.json, and a custom ANTHROPIC_BASE_URL that doesn’t support prompt-caching-scope-2026-01-05, the beta header is still sent, causing API errors when using claude-4.5-opus model.

Common causes

• Even when users explicitly disable prompt caching in VS Code settings (claudeCode.enablePromptCaching: false) and unset beta headers (claudeCode.useAnthropicBetaHeaders: false), Claude Code v2.1.23 still sends the ‘prompt-caching-scope-2026-01-05’ beta header to custom API endpoints. This breaks integration with self-hosted or proxy API servers that don’t support the beta.
• GitHub issue #21644 in anthropics/claude-code: With enablePromptCaching=false and useAnthropicBetaHeaders=false set in VS Code settings.json, and a custom ANTHROPIC_BASE_URL that doesn’t support prompt-caching-scope-2026-01-05, the beta header is still sent, causing API errors when using claude-4.5-opus model.

Quick fixes

1. Confirm the exact error signature matches API error 400: The provider does not support the prompt-caching-scope-2026-01-05 beta header.
2. Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/anthropics/claude-code/issues/21644

Evidence note: GitHub issue #21644 in anthropics/claude-code: With enablePromptCaching=false and useAnthropicBetaHeaders=false set in VS Code settings.json, and a custom ANTHROPIC_BASE_URL that doesn’t support prompt-caching-scope-2026-01-05, the beta header is still sent, causing API errors when using claude-4.5-opus model.

Related errors

• Claude Code ANTHROPIC_BASE_URL custom endpoint errors
• Claude Code prompt caching header ignored settings
• Custom Claude API proxy beta header issues

FAQ

What should I check first?

Start with the exact API error 400: The provider does not support the prompt-caching-scope-2026-01-05 beta header text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Claude Code workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without API error 400: The provider does not support the prompt-caching-scope-2026-01-05 beta header.