LiteLLM
OSS proxy that normalizes 100+ LLMs to the OpenAI format. Add routing, fallbacks, caching, and cost tracking in one layer.
AutoGen
Microsoft research framework for building multi-agent systems through conversational patterns. Officially superseded by Microsoft Agent Framework 1.0 (April 2026), which merges AutoGen and Semantic Kernel. Large installed base remains; Microsoft publishes a migration path.