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.
Mem0
Open-source persistent memory layer that gives AI agents the ability to remember users, preferences, and context across sessions. Supports vector, graph, and key-value storage backends. AWS partner for Strands Agents. YC W23, $24M raised, 30K+ GitHub stars.