ModelCatalog class final

Allowlist of supported embedding models for dense retrieval.

ModelCatalog is the single place where models are registered and the concrete AllowlistProvider implementation used with ModelDownloader. All models must appear here before they can be downloaded — attempting to look up an unregistered model ID throws ArgumentError. Attempting to load a model whose validation flag is false throws UnsupportedError.

Why AllowlistProvider

ModelCatalog implements AllowlistProvider from betto_onnxrt so that ModelDownloader can be constructed with allowlist: ModelCatalog() and will reject any model not in this catalog before touching the network.

Adding a new model

1. Add a private ModelSpec field below (as a static final).
2. Insert it into the _catalog map with its ID as the key.
3. Add '<id>': false to _validated until the model has been tested in CI; flip it to true when the validation plan is complete.

Usage

final spec = ModelCatalog.lookup('bge-small-en-v1.5');
print(spec.meta['dimensions']); // 384

// Use with ModelDownloader to gate downloads:
final downloader = ModelDownloader(allowlist: ModelCatalog());