Custom model ids (#97928): a value of image_gen.openai.model / OPENAI_IMAGE_MODEL outside the
gpt-image-2 / gpt-image-2.5 catalog used to fall through silently to the default tier, so a
gateway serving its own image model names always received `model: gpt-image-2` +
`quality: medium`. resolve_static_model(passthrough=True) now returns the unknown id as the
API model with quality=None, and the request omits `quality` for it — OpenAI-compatible
gateways reject enum values they do not know, and a foreign model has no OpenAI quality
tiers. Only the provider-scoped key and env var pass through; the shared top-level
image_gen.model can hold another provider's id (a FAL path) and is never forwarded.
Named custom endpoint (#83080, config-reuse half): image_gen.openai.provider names a
providers:/custom_providers: entry; its base_url and api_key/key_env fill in whatever
image_gen.openai.base_url / key_env leave unset, so a gateway already declared for chat is
not re-declared with a duplicated key. Explicit image_gen.openai values keep precedence; an
unknown name logs a warning and falls back to the OpenAI variables. The lookup goes through
hermes_cli.runtime_provider._get_named_custom_provider, the same resolver the auxiliary
clients use, so aliases and legacy list entries behave identically.
image_gen is an open config root (deliberately absent from DEFAULT_CONFIG), so
`image_gen.openai.provider` already validates as a known key; docs cover both behaviours.
Live probe (fake /v1/images/generations gateway recording the body, real provider on a temp
HERMES_HOME): before — `custom-image-model` sent as model=gpt-image-2 quality=medium; named
provider → is_available False / auth_required. After — model=custom-image-model, no quality;
named provider → request to the entry's URL with `Bearer <its key_env>`; the catalog model
still maps to gpt-image-2 + quality=medium.
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