Agentic Frameworks Explained: FastAgent vs LangGraph vs Pydantic AI

Agentic frameworks explained: compare FastAgent, LangGraph and Pydantic AI, then understand custom harnesses, the Claude Agent SDK and managed agents. Learn who chooses the next step, how state and validation work, and who operates the runtime. This visual lesson covers: • Reusable agent infrastructure versus your application logic • FastAgent model-led execution, MCP and workflow composition • LangGraph nodes, edges, shared state, branching and checkpoints • Human approval, resume behavior and safe handling of repeated side effects • Pydantic AI typed results, validation and dependency injection • Model-driven, workflow-driven and hybrid architectures • Custom harnesses, frameworks, agent SDKs and managed services • Claude cloud and self-hosted sandbox options CHAPTERS 00:00 Agentic Frameworks: Reuse the Machinery 00:46 FastAgent: Model-Led Execution 01:32 LangGraph: State, Nodes and Edges 02:13 Shared State: Read, Work, Update 02:58 Branch, Pause and Resume 03:46 Pydantic AI: Typed, Validated Results 04:33 Dependencies: Connect Agents to Your App 05:26 Three Frameworks, Three Emphases 06:17 Model-Driven and Workflow-Driven 07:02 Who Builds and Operates the Machinery? 07:51 Claude Agent SDK vs Managed Agents 08:42 Choose by Responsibility and Control Key distinctions: schema validation does not establish factual truth; interrupted graph nodes may replay; framework categories overlap. Product capabilities were checked against primary documentation on September 25, 2026. PRIMARY SOURCES FastAgent: https://fast-agent.ai/ FastAgent workflows: https://fast-agent.ai/agents/workflows/ LangGraph state and graphs: https://docs.langchain.com/oss/python/lang... LangGraph persistence: https://docs.langchain.com/oss/python/lang... LangGraph approval and replay: https://docs.langchain.com/oss/python/lang... Pydantic AI: https://pydantic.dev/docs/ai/overview/ Typed output: https://pydantic.dev/docs/ai/core-concepts... Dependencies: https://pydantic.dev/docs/ai/core-concepts... Claude Agent SDK: https://code.claude.com/docs/en/agent-sdk/... Claude Managed Agents: https://platform.claude.com/docs/en/manage... For developers learning agentic AI, LLM application architecture and practical orchestration. Subscribe to Core Concept Learning for clear, visual explanations of AI and software engineering concepts.    / @coreconceptlearning   #AgenticAI #LangGraph #PydanticAI