Add metadata field to ModelMessage #3404
Description
Description
Summary
This feature request is to add a new, optional metadata: dict[str, Any] | None field to both the ModelRequest and ModelResponse. This field would serve as a "user-space" container for arbitrary, application-specific data that is not sent to the LLM.
Problem & Motivation
Developers often need to tag messages for filtering, grouping, or post-processing based on their application's internal logic. However, currently, there is no dedicated field on message objects to attach custom, application-specific data.
For example, an application might need to decorate the user's raw input before sending it as a ModelRequest. With a metadata field, developers could easily track which messages are customized and which template was used, enabling more reliable filtering or post-processing. Without metadata, we currently have to rely on detecting special characters in the message, which is error-prone.
A dedicated metadata field provides a clean, and simple way to store this information directly on the message object, improving developer experience and code robustness.
References
No response