LiteLLM settings: configured model ID silently reverts to default and cannot be changed

[easonLiangWorldedtech]

Description

With the LiteLLM provider, the model ID on the settings screen cannot be changed: after picking a model (e.g. via "Use custom model..."), the picker silently reverts to the hardcoded default (claude-3-7-sonnet-20250219). The user's selection is not displayed afterwards, so the setting appears broken.

Steps to reproduce

1. Open Settings → Providers → LiteLLM.
2. Set the base URL and API key, then refresh the model list.
3. Pick a model ID that is not present in the fetched /models list (e.g. a custom alias) via "Use custom model...".
4. The picker immediately reverts to the default model ID.
5. Save, close and reopen Settings — the configured model ID is not shown; the default is shown instead.

Root cause

The LiteLLM case in webview-ui/src/components/ui/hooks/useSelectedModel.ts validates the configured litellmModelId against the fetched router-model list and, when it is absent, substitutes the hardcoded default via getValidatedModelId(). LiteLLM is a proxy that fronts arbitrary models and aliases, so a configured ID is the user's explicit selection even when it is absent from the fetched list (custom aliases, incomplete or stale listings, renamed deployments).

Expected behavior

• A configured litellmModelId is displayed and preserved, regardless of whether it appears in the fetched list.
• The hardcoded default is only used when nothing is configured and a populated list exists.