[Help needed] Anthropic Caching filter: Can filter only access user/assistant messages and not system ?

[thiswillbeyourgithub]

Hi,

I was trying to make a simple filter (NOT using pipelines, I want to make it simple for others to install) that automatically modifies the system message to use caching for anthropic models. But after coding a draft it appears that the body my inlet receives only contains user and assistant messages, but no system prompts.

Is that a bug or on purpose? I have to say it's surprising to me that an inlet filter would only access the user/assistant message and not all chat messages at it severely reduces its potential applications to my eyes.

Here's my draft if you want to take a look: https://github.com/thiswillbeyourgithub/openwebui_custom_pipes_filters/blob/main/filters/WIP_automatic_claude_caching.py