Summary

agent_cfg prepends base.yaml unless some config path contains the substring base. That fires on database.yaml and my_base_model.yaml, so -c those files never got the agent system/instance templates and the run failed in pydantic.

Match on the filename base.yaml instead (including configs/base.yaml).

Test plan

• database.yaml and my_base_model.yaml get base.yaml prepended
• configs/base.yaml is left as the base, not doubled
• existing model_gateway.yaml / explicit base.yaml cases still pass