### Check for existing issues

- [x] I have searched the existing issues and checked that my issue is not a duplicate.

### What happened?

We have a litellm instance with OpenRouter and Vertex providing Calude Sonnet 4.5 models. We use the instance together with Kilo Code and Roo Code. Recently we've started to get a lot errors from both of them about "tool calling" failure. For example:

`Kilo Code tried to use write_to_file without value for required parameter 'content'. Retrying...`

Further investigation showed that the tool calling responses coming from litellm are not complete.

### Steps to Reproduce

1. Set up any version of LiteLLM (we have tested every version from v1.75 to v1.81.3) 2. Set up either Vertex or OpenRouter with Sonnet 4.5 3. Try below curl which is an example I've reconstructed from Kilo Code logs

``` curl --location '[BASE_URL]' \ --header 'Content-Type: application/json' \ --header 'Authorization: Bearer [API_KEY]' \ --data '{ "model": "[REPLACE WITH LITELLM MODEL NAME -> claude-sonnet-4-5]", "messages": [ { "role": "user", "content": "Imagine a service like n8n. Think about how to implement it, then write down the plan to a markdown file…