LiteLLM / LiteLLM
LiteLLM Presidio Guardrail PII Masking Broken with Anthropic Native API
Fix LiteLLM Presidio PII guardrail not working with Anthropic native API path Includes evidence for LiteLLM troubleshooting demand.
- Category
- LiteLLM
- Error signature
Presidio guardrail: PII masked on input but never unmasked in responses, 400 error with tools- Quick fix
- Compare the failing environment with a known working setup, then change one configuration value at a time.
- Updated
What this error means
Presidio guardrail: PII masked on input but never unmasked in responses, 400 error with tools is a LiteLLM failure pattern reported for developers trying to fix litellm presidio pii guardrail not working with anthropic native api path. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.
Why this happens
When using Anthropic native API path with Presidio guardrail and output_parse_pii=true, PII is masked on input but never unmasked in responses. Using tools (e.g. via Claude Code) causes 400 error.
Common causes
- PII masking is a critical security/compliance feature for enterprise users of LiteLLM proxy. When it silently fails, sensitive data leaks — a severe compliance risk.
- When using Anthropic native API path with Presidio guardrail and output_parse_pii=true, PII is masked on input but never unmasked in responses. Using tools (e.g. via Claude Code) causes 400 error.
Quick fixes
- Confirm the exact error signature matches
Presidio guardrail: PII masked on input but never unmasked in responses, 400 error with tools. - Check the LiteLLM account, local tool state, and provider configuration involved in the failing workflow.
- 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
- Capture the exact error message and the command, editor action, or request that triggered it.
- Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
- Review the source evidence below and compare it with your environment.
- Apply one change at a time and rerun the smallest failing action.
- 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
Evidence note: When using Anthropic native API path with Presidio guardrail and output_parse_pii=true, PII is masked on input but never unmasked in responses. Using tools (e.g. via Claude Code) causes 400 error.
Related errors
- LiteLLM guardrail bypass
- LiteLLM PII leak
- LiteLLM Anthropic 400 error
FAQ
What should I check first?
Start with the exact Presidio guardrail: PII masked on input but never unmasked in responses, 400 error with tools text and the smallest action that reproduces it.
Can I ignore this error?
No. Treat it as a failed LiteLLM 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 Presidio guardrail: PII masked on input but never unmasked in responses, 400 error with tools.