These tools integrates with
LettavsOpenAI API
Stateful agents with long-term memory — formerly MemGPT versus GPT-5 era models, embeddings, and Responses API from OpenAI
Compare interactively in Explore →Choose Letta when…
- •need agents with persistent cross-session memory
- •context window length is limiting your application
- •building personal assistants or long-running agents
Choose OpenAI API when…
- •You need the broadest ecosystem and most integrations
- •GPT-4 or o-series reasoning models are required
- •Assistants API, fine-tuning, or batch API are needed
Side-by-side comparison
Field
Letta
OpenAI API
Category
Agent Frameworks
LLM Infrastructure
Type
Open Source
Commercial
Free Tier
✓ Yes
✗ No
Pricing Plans
Open Source: FreeCloud: $20/mo
API: Per token
GitHub Stars
⭐ 13,200
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Health
●100 — Active
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Letta
Letta (formerly MemGPT) is an open-source framework for building stateful AI agents with persistent, editable memory. Agents remember conversations across sessions, search their own memory, and update their knowledge over time — solving context window limitations.
OpenAI API
API access to GPT-5, GPT-5.5, o3/o4 reasoning models, and the Responses API; plus embeddings, image, audio, and Realtime endpoints. The most widely deployed LLM API in production.
Only Letta (2)
LangGraphOpenAI API
Only OpenAI API (39)
CrewAIAutoGenLlamaIndexLangChainPydanticAIsmolagentsAgnoMastraLiteLLMPortKey
Explore the full AI landscape
See how Letta and OpenAI API fit into the bigger picture — 235 tools, 543 relationships, all mapped.