Add optional timestamp to SystemPromptPart

[JohnUiterwyk]

UserPromptPart, ToolReturnPart, RetryPromptPart all include a timestamp attribute.
As do TextPart, ToolCallPart.

SystemPromptPart is the only part type in the ModelRequestPart that does not have a timestamp.

There are times that we create a system prompt instance from a template, and this instantiation is done at particular point in time. There are also times when this happens in other systems, and that history is passed to our pydantic-ai service, and the timestamp is consider a required attribute as part of retaining an immutable timestamped sequence of entries related to a user/ai chat.

Can we please add

    timestamp: datetime = field(default_factory=_now_utc)

to SystemPromptPart to bring it in line with the other parts

[Kludex]

PR welcome! 🙏

[vricciardulli]

Just opened a PR about this, but I didn't see there was another open already. Feel free to close it if redundant

[Kludex]

• Closed by Add timestamp to SystemPromptPart #1154

[JohnUiterwyk]

thank you!