Supersession

Retiring a belief by marking when it stopped being true (invalid_at) and what replaced it (superseded_by), rather than removing it.

Why it matters in a memory layer

It costs one nullable timestamp and buys every historical question: where do I work and where did I work before both stay answerable, and any belief the system once held can be explained. Deletion answers the first and destroys the rest permanently. The date matters too — a belief is invalid from the moment its replacement became true, which is event time, not when the system found out. Genuine erasure is a different operation for a different reason, and it is a governance obligation rather than an update.

Connections

Taught in: Supersede, Never Destroy

Used in: From Facts to a User Model · Promotion as a Release · Sleep-Time Compute · Two Clocks · Validity Intervals · Why Memory Eval Is Hard · Forgetting Under a Budget · Hybrid Architecture · Scope, Then Rank · Vector Stores for Data That Changes · Why Forgetting Is a Feature