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 Officially superseded by Microsoft Agent Framework 1.0 (April 2026), which merges AutoGen and Semantic Kernel.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.
Anthropic API
API access to Claude model family including Claude 3.5 Sonnet, Haiku, and Opus. Excels at coding, analysis, long-context tasks, and safety-critical applications.