There's no way to explicitly remove a key from a model's `litellm_params` via `PATCH /model/{id}/update`. Observed behavior: omitting a field preserves the old value (expected); explicitly setting it to `null` **also** preserves the old value (unexpected); only a non-null replacement actually takes effect. The only workaround found was a direct Postgres `litellm_params - 'key'` JSONB delete, bypassing the management API.

Concretely hit this with `cache_control_injection_points`: setting it to `[]` to mean "disabled" left a stored empty list rather than clearing the key. After an unrelated restart re-read the config, that stored `[]` began being forwarded as a literal request parameter to the model provider, breaking every request through that model entry with `Extra inputs are not permitted`.

**Suggested fix:** give explicit `null` real delete semantics (distinct from omission), or add a dedicated field-removal mechanism to the update endpoint.