Add validate_config_structure() that catches common config.yaml mistakes:
- custom_providers as dict instead of list (missing '-' in YAML)
- fallback_model accidentally nested inside another section
- custom_providers entries missing required fields (name, base_url)
- Missing model section when custom_providers is configured
- Root-level keys that look like misplaced custom_providers fields
Surface these diagnostics at three levels:
1. Startup: print_config_warnings() runs at CLI and gateway module load,
so users see issues before hitting cryptic errors
2. Error time: 'Unknown provider' errors in auth.py and model_switch.py
now include config diagnostics with fix suggestions
3. Doctor: 'hermes doctor' shows a Config Structure section with all
issues and fix hints
Also adds a warning log in runtime_provider.py when custom_providers
is a dict (previously returned None silently).
Motivated by a Discord user who had malformed custom_providers YAML
and got only 'Unknown Provider' with no guidance on what was wrong.
17 new tests covering all validation paths.
dce5f51c7c