> For AI agents: the complete documentation index is available at https://mfeflow.github.io/mfeflow/llms.txt, the full documentation bundle is available at https://mfeflow.github.io/mfeflow/llms-full.txt.

# MFEFLOW_E506

The registry host is not set up or cannot be used.

## Fix

Pass --host file:<dir> or s3://<bucket>\[/prefix], or set registry.host in mfeflow\.json. Deploys also need --base-url or registry.baseUrl. S3 settings come from MFEFLOW_S3_ENDPOINT, MFEFLOW_S3_REGION, AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY. See [https://mfeflow.github.io/mfeflow/guide/deploy-and-rollback](https://mfeflow.github.io/mfeflow/guide/deploy-and-rollback).