Letta vs Zep: open-source agent memory vs production memory layer in 2026
Letta (formerly MemGPT) is the OSS virtual-context agent framework. Zep is the production memory layer with temporal facts + Graphiti knowledge graph. Pick Letta for OSS + virtual context, Zep for production.
At a glance
| Dimension | Letta (MemGPT) | Zep |
|---|---|---|
| Form factor | OSS framework | Hosted + OSS service |
| Memory architecture | Virtual context (main + archival) | Temporal facts + Graphiti knowledge graphWIN |
| Knowledge graph | No | First class (Graphiti)WIN |
| Production maturity | Growing OSS adoption | Production-grade hosted + OSSWIN |
| API ergonomics | Python-first | REST + Python + TS SDKsWIN |
| Setup complexity | Self-host required | Hosted or self-hostWIN |
| Cost | Free OSS + computeWIN | Per-seat + per-op |
| Best for | Research + OSS exploration | Production agent memory |
Verdict
Letta is the right pick for research, OSS-preferring stacks, and teams exploring the virtual-context memory pattern Letta pioneered. Zep is the right pick for production agent memory — temporal facts, knowledge graph via Graphiti, and ergonomic SDKs make it the production default in 2026. For OSS / research, Letta. For shipping agent memory in production, Zep.
When to pick which
Pick Letta (MemGPT)
OSS / research, virtual-context exploration.
Pick Zep
Production agent memory, temporal facts, knowledge graph.
FAQ
Letta or Zep for production?
Zep — production memory layer with stronger ergonomics in 2026.
Best free agent memory?
Letta (OSS) or Mem0 (OSS + cloud).
Best for knowledge graph memory?
Zep — Graphiti is first class.
Last updated: 2026-06-01.