## Summary

LiteLLM runtime supports dict-based fallback entries, but the Admin UI router settings page appears to assume fallback entries are strings only.

When `router_settings.fallbacks` contains an advanced fallback object like:

```yaml router_settings: fallbacks: - primary-model: - model: fallback-model api_key: "..." extra_headers: {} ```

the router works with this shape, but the Admin UI crashes when viewing router settings.

Browser console error:

```text Uncaught Error: Minified React error #31; visit https://react.dev/errors/31?args[]=object%20with%20keys%20%7Bmodel%2C%20api_key%2C%20extra_headers%7D ```

This looks like the UI is trying to render the fallback object directly as a React child.

## Why this matters

This fallback shape is useful for real cases where fallback must override request-level auth.

Example:

- primary model uses auth injected by a proxy/custom hook - request fails and falls back to another model/provider - fallback must explicitly replace stale `api_key` / `Authorization` state

Without dict-based fallback entries, standard string fallback can reuse the wrong auth across fallback attempts.

## Repro

1. Star…