# models catalog The `models` extension keeps a local copy of the [models.dev](https://models.dev) catalog and answers one question for the rest of Albedo: what is actually known about this model and its provider. It never guesses a limit from a model name. It is enabled by default and contributes no model tools and no prompt context. ## cache The catalog is cached at `$ALBEDO_HOME/models.json` (default `~/.albedo/models.json`). Albedo refreshes it when it is missing or older than the refresh window, in the background, and writes it by rename so a partial download is never readable. A failed fetch keeps the previous cache, and the whole file stays as models.dev published it. ```json { "models": { "url": "https://models.dev/api.json", "refreshHours": 24 } } ``` Put this in `$ALBEDO_HOME/extensions.json`. `refreshHours: 0` disables automatic fetching and uses only the cached file, which is what the test suite and air-gapped hosts do. Only `https`, or `http` on the loopback host, is fetched. Run `/reload models` to fetch the configured catalog immediately, regardless of its age or `refreshHours`. The command returns only after the cache has been atomically replaced, so the next `/model` picker reads the new model list. A failed fetch leaves the previous cache in place and reports the failure. ## lookup A lookup takes the session's model id and its configured provider base url. The endpoint decides between providers that publish the same model id. Without a host match, candidates that agree still answer, and candidates that disagree stay unknown rather than picking one. Both the catalog key and its trailing segment resolve, so `vendor/model` and `model` find the same entry. An answer carries the context window, the maximum output, the input modalities, the provider id, its documented API endpoint, and its expected environment variable names. Everything is reported with its source: the cached file and how the model was matched. ## used by `rolling` compaction asks for the context window when `contextWindow…