LiteLLM constructs incorrect Vertex AI base URL for us/eu multi-region endpoints

What this error means

LiteLLM Vertex AI: wrong base URL for us/eu multi-region endpoints is a LiteLLM failure pattern reported for developers trying to fix litellm wrong vertex ai url construction for us/eu multi-region endpoints. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Google introduced multi-region endpoints (us, eu) on April 16, 2026. LiteLLM’s get_vertex_base_url() constructs wrong URLs. Generated URLs don’t exist and return HTML error pages. Fix: use aiplatform.{region}.rep.googleapis.com format.

Common causes

• LiteLLM generates wrong URLs (us-aiplatform.googleapis.com instead of aiplatform.us.rep.googleapis.com) for new Vertex AI multi-region endpoints
• Google introduced multi-region endpoints (us, eu) on April 16, 2026. LiteLLM’s get_vertex_base_url() constructs wrong URLs. Generated URLs don’t exist and return HTML error pages. Fix: use aiplatform.{region}.rep.googleapis.com format.

Quick fixes

1. Confirm the exact error signature matches LiteLLM Vertex AI: wrong base URL for us/eu multi-region endpoints.
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/25926

Evidence note: Google introduced multi-region endpoints (us, eu) on April 16, 2026. LiteLLM’s get_vertex_base_url() constructs wrong URLs. Generated URLs don’t exist and return HTML error pages. Fix: use aiplatform.{region}.rep.googleapis.com format.

Related errors

• Claude Code Bedrock beta flag 400
• LiteLLM additional_drop_params ignored

FAQ

What should I check first?

Start with the exact LiteLLM Vertex AI: wrong base URL for us/eu multi-region endpoints 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 LiteLLM Vertex AI: wrong base URL for us/eu multi-region endpoints.