How do you track product decisions so you don’t lose the original reasoning months later?

In a previous role, we shipped a feature that didn’t move the metric we expected.

When leadership asked why we built it, we struggled to clearly show:

• What evidence we had at the time

• What assumptions we were making

• Who aligned on the decision

Most of the context was buried in Slack threads and meeting notes.

I’m curious — how do you all track product decisions beyond just PRDs and Jira tickets?

Do you maintain a separate decision log? Or does it naturally live in your docs?

Genuinely trying to learn how others handle this.