UnsupportedParamsError when using litellm with perplexity/sonar model

[amit-y11]

Describe the bug
I am encountering an UnsupportedParamsError when using the perplexity/sonar model via LiteLLM. The error message indicates that the sonar model does not support parameter 'tools'. The underlying litellm library suggests setting litellm.drop_params=True to resolve this. But, the current implementation of google.adk.models.lite_llm.LiteLlmdoes not provide a direct way to pass this drop_params configuration to the underlying litellm.completion or litellm.acompletion calls on a per-instance basis.

Error Message

An error occurred: litellm.UnsupportedParamsError: perplexity does not support parameters: ['tools'], for model=sonar. To drop these, set `litellm.drop_params=True` or for proxy:

`litellm_settings:
 drop_params: true`

 If you want to use these params dynamically send allowed_openai_params=['tools'] in your request.

To Reproduce
Steps to reproduce the behavior:

1. Install litellm
2. create an agent with perplexity/sonar model using litellm

Expected behavior
I expect to be able to configure drop_params when initializing LiteLlm from google.adk.models.lite_llm, similar to how other LiteLLM-specific parameters might be passed. This would allow me to gracefully handle models that do not support certain parameters (like tools) without having to set litellm.drop_params = True globally.

Desktop (please complete the following information):

• OS: macOS
• Python version(python -V): 3.13.5
• ADK version(pip show google-adk): 1.5.0
• litellm version: 1.73.6

Model Information:
perplexity/sonar

Additional context
Add any other context about the problem here.