Claude Code + LiteLLM Gateway — Multi-turn Conversation Hangs with Validation Errors

What this error means

API Error: 400 litellm.BadRequestError: 178 validation errors on multi-turn conversation is a LiteLLM failure pattern reported for developers trying to fix claude code multi-turn conversation failing through litellm proxy gateway. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Claude Code calling LiteLLM gateway returns API Error 400 with 178 validation errors. Input type mismatch: string_type validation fails on array input. Affects multi-turn conversations specifically.

Common causes

• Claude Code using LiteLLM as proxy gateway; multi-turn conversations fail with 178 validation errors; blocks entire workflow
• Claude Code calling LiteLLM gateway returns API Error 400 with 178 validation errors. Input type mismatch: string_type validation fails on array input. Affects multi-turn conversations specifically.

Quick fixes

1. Confirm the exact error signature matches API Error: 400 litellm.BadRequestError: 178 validation errors on multi-turn conversation.
2. Check the LiteLLM 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/BerriAI/litellm/issues/27839

Evidence note: Claude Code calling LiteLLM gateway returns API Error 400 with 178 validation errors. Input type mismatch: string_type validation fails on array input. Affects multi-turn conversations specifically.

Related errors

• Claude Code LiteLLM proxy error
• LiteLLM validation error multi-turn

FAQ

What should I check first?

Start with the exact API Error: 400 litellm.BadRequestError: 178 validation errors on multi-turn conversation 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 API Error: 400 litellm.BadRequestError: 178 validation errors on multi-turn conversation.