Summary

When using the Claude GitHub Action with use_vertex: true, the action fails unless both CLOUD_ML_REGION and the corresponding model-specific VERTEX_REGION_CLAUDE_* environment variable are set.

I assumed CLOUD_ML_REGION to act as a global default for all Vertex AI models, but that does not appear to be the case.

If CLOUD_ML_REGION is omitted, the action fails with:

API Error: No region was given. The client should be instantiated with the `region` option or the `CLOUD_ML_REGION` environment variable should be set.

If the model-specific variable (VERTEX_REGION_CLAUDE_3_7_SONNET in this case) is omitted the run also fails with:

API Error: No region was given. The client should be instantiated with the `region` option or the `CLOUD_ML_REGION` environment variable should be set.

Expected Behavior

Setting CLOUD_ML_REGION should be sufficient to route all models through Vertex AI unless explicitly overridden by a model-specific variable.

Request

• Support CLOUD_ML_REGION as a global default across all models
• If model-specific region variables are required, document the full list and precedence behavior