[FR]: Error field support in metrics constructor / default error chart

[seldereyy]

Proposal summary

Currently, when logging errors, Opik adds an Error field to the input/output section. However, this field is not accessible in the online evaluation → code metric constructor.

Because of this limitation, it’s not possible to track the dynamics of error frequency in the UI.

I’d like to request one of the following improvements:

1. Add a default chart for errors (e.g., error count over time), possibly with breakdowns by error type or by agent that generated the error.
2. Expose the Error field in the metrics constructor, so that custom metrics can leverage it directly.

Motivation

This would make it easier to monitor system reliability and evaluate error trends without additional workarounds.

[juanferrub]

Thanks so much for sharing this feedback, @seldereyy 🙏

It would be really helpful to understand a bit more about your needs: what kinds of errors are you most interested in tracking? Also, what’s the underlying use case where metrics that capture errors would provide the most value for you?

This context will help us think through the best solution
Best,
Juan