# Memory eviction and forgetting in AI agents

## Metadata

| Field | Value |
|---|---|
| Institute | Molodetz Institute — Research & Retrieval Division |
| Subject | agent-memory-recency-tracking |
| Document type | Source Dossier |
| Tier | 1 |
| Source title | Memory eviction and forgetting in AI agents |
| Source URL | https://mem0.ai/blog/memory-eviction-and-forgetting-in-ai-agents |
| Source publisher / author | Mem0 (vendor blog) |
| Source type | blog post / vendor docs |
| Source date (published) | Unknown — not stated |
| Date researched | 2026-10-09 |
| Researched by | tai (agent), model: Claude Sonnet 5, on behalf of retoor |
| Research method | web search synthesis |
| Confidence | Medium |
| Status | Active |

## Summary

Mem0's broader guidance on eviction/forgetting beyond the Memory Decay feature specifically: it distinguishes soft re-ranking (decay) from real pruning, and recommends TTL policies plus explicit deletion APIs for genuine forgetting, with tiered memory lifetimes by scope.

## Key findings

- Session memory is described as persisting minutes-to-hours and being cleared explicitly; user- and organization-level memory are long-lived by contrast.
- For episodic data specifically, the guidance is to use timestamps plus explicit TTL policies rather than relying on decay alone.
- The source explicitly states memory systems need deletion APIs and UX patterns that expose what is remembered — i.e. forgetting should be an observable, intentional operation, not an opaque side effect.
- Decay (see `mem0-introducing-memory-decay.md`) is characterized here as "decays low-relevance entries over time, freeing up space and attention" — a description, not a documented formula.

## Pros / strengths

- Clearly separates three distinct concerns that are easy to conflate: ranking (decay), lifecycle/expiry (TTL), and user-visible deletion (explicit API) — a useful three-way framework for tai to keep in mind even though only the tracking substrate for the first concern is being built right now.

## Cons / limitations / caveats

- Lacks a documented formula for its own decay mechanism (consistent with the companion decay-announcement post); this source is guidance-level, not implementation-level detail.
- Vendor content, not independently verified.

## Relevance to tai

Useful for correctly scoping what tai's `last_used`/`use_count` proposal is and is not: it is tracking substrate that could later feed a decay-style ranking signal (per Mem0's own distinction), but it is explicitly not a TTL/expiry mechanism and not a deletion mechanism — those would be separate, later decisions if ever made.

## Changelog

| Date | Change |
|---|---|
| 2026-10-09 | Initial dossier created. |