# Supersession, decay, and forget

Three mechanisms for how beliefs change, fade, and are removed.

Most memory products conflate three different questions into a single “delete” or “rank lower” behaviour. That is why teams discover too late that a correction was lost, a stale preference still wins at retrieval time, or an erasure request left records in a backup table nobody queries.

SurrealDB Agent Memory separates them on purpose:

| Question | Mechanism | Example |
| --- | --- | --- |
| **“This replaced that.”** | **Supersession** | You preferred formal tone in March; you prefer casual now. The old instruction stays in history with a bounded validity interval; the new one is current. |
| **“This stopped being relevant.”** | **Decay with reinforcement** | A sprint goal from three weeks ago fades unless retrieval keeps using it. |
| **“This should not exist for the agent.”** | **Forget** (soft by default) | “Forget everything about my old job.” Matched beliefs expire from current retrieval; see [Forgetting memories](/docs/agent-memory/operations/forget.md). |

Conflating these into one overwrite or one ranking pool is a common reason agent memory fails in production: you either lose the audit trail or you let two “current” beliefs fight at query time.

## Supersession - replacement with history

When an updated preference or corrected fact arrives from the **same kind of source** (for example two statements from the same user over time), SurrealDB Agent Memory treats it as **you changing your mind**, not a contradiction to flag.

- The prior belief is **closed in time**, not erased.
- The new belief becomes the **single current answer** for “what is true now?”
- You can still ask what the value was last month and when it changed.

Instructions behave the same way: “always use formal tone” superseded by “prefer casual” means the agent follows casual **now**, but the shift remains auditable.

Cross-provenance clashes are different - an uploaded policy versus a user assertion - and surface as **`uncertainty`** instead of a clean supersession. See [Authority when pillars meet](/docs/agent-memory/reasoning/authority-hierarchy.md).

## Decay - relevance without destruction

Not everything should live at full strength forever. **Context** fades quickly; **knowledge** fades more slowly; **identity** is comparatively stable. SurrealDB Agent Memory applies category-aware **importance decay** on a schedule.

Decay is not blind deletion: when a memory contributes to a successful retrieval, its importance can be **reinforced** so useful facts stay sharp while untouched noise quietly leaves the active set.

Background **consolidation** can also crystallise repeated observations into durable beliefs (`source.kind = "consolidation"`) - the “between conversations” evolution described in [Traces and memory evolution](/docs/agent-memory/architecture/traces-and-evolution.md).

## Forget - explicit removal

When something must stop influencing the agent - privacy, compliance, or a hard reset - use **`POST /forget`** or entity delete. Default behaviour **expires** matched records from current retrieval while keeping audit history; **`purge: true`** and scoped forget exist for erasure requirements.

Forget does not block future extraction: if a later turn mentions the same topic again, new memory can be created. Combine product policy with forget when a topic must stay gone.

## Long sessions and compaction

Existing model context windows encourage **compaction**, namely the process of squashing a long thread into a summary. Summaries are inherently lossy, often discarding details you did not know you would need later.

SurrealDB Agent Memory’s approach is complementary: important facts from turns are **promoted into durable, queryable memory** (entities, attributes, instructions) while the **full episodic transcript** remains addressable via sessions and provenance. Consolidation and reflection run **between** interactions so you are not dependent on remembering to compact at the right moment for memory to survive the next session.

## Who owns the decision?

The **reconciler** owns the bookkeeping guarantees - supersession chains, confidence floors, decay schedules, uncertainty when sources disagree. **Signals** come from agent actions: turns, corrections, document ingest, reflection, and traces of what was retrieved and used.

When the system genuinely cannot decide (cross-provenance conflict, confidence below the calibration floor), it records **`uncertainty`** for the agent or a higher-level policy to resolve rather than silently picking a winner.

## Related reading

- [Reconciliation and supersession](/docs/agent-memory/reasoning/reconciliation-and-supersession.md)
- [Tri-temporal model](/docs/agent-memory/architecture/tri-temporal-model.md)
- [Forgetting memories](/docs/agent-memory/operations/forget.md)
- [Traces and memory evolution](/docs/agent-memory/architecture/traces-and-evolution.md)