## What happened?

In LiteLLM Admin UI, when adding a model with provider `OpenRouter`, I selected `openrouter/google/gemini-2.5-flash` directly from the provider model list/dropdown.

When I click `Test Connect`, the request fails with:

```text OpenrouterException - {"error":{"message":"openrouter/google/gemini-2.5-flash is not a valid model ID","code":400},"user_id":"..."} ```

This does not appear to be a manual input error, because the model was selected from the OpenRouter model list in the UI.

## Why this seems incorrect

As of March 30, 2026, `google/gemini-2.5-flash` still exists on OpenRouter: https://openrouter.ai/google/gemini-2.5-flash

So either: 1. LiteLLM Admin UI is surfacing a stale or invalid OpenRouter model ID. 2. The `Test Connect` flow is sending a model name format that OpenRouter rejects. 3. There is a mismatch between what the dropdown returns and what the backend/OpenRouter expects.

## Reproduction

1. Open LiteLLM Admin UI. 2. Go to `Models + Endpoints` -> `Add Model`. 3. Choose provider: `OpenRouter`. 4. Select model from the provider model list: `openrouter/google/gemini-2.5-flash`. 5. Click `Test Connect`.

## Actual result

Connection test fails wi…