LangChain is a comprehensive framework for building LLM-powered applications. It provides core abstractions for language models, prompts, chains, agents, memory, and tools, enabling developers to create complex AI systems like chatbots, question-answering agents, and retrieval-augmented generation pipelines. The architecture is modular with clear separation between core langchain_core foundations, legacy langchain_classic components (many deprecated), and partner integrations for specific LLM providers and vector stores. Key entry points include agent creation functions, chain constructors, and memory/retriever interfaces. The framework emphasizes composability through the Runnable interface (LCEL) and supports both synchronous and asynchronous operations. While extensive, the codebase shows strong maintenance practices with active dependency management and version consistency checks across integrations.

LangGraph is a production-grade Python framework for building stateful, resumable, multi-step LLM agent workflows, distributed as a monorepo of Python packages (core `langgraph`, `langgraph-sdk`, `langgraph-cli`, checkpoint backends, prebuilt agents) plus JS/TS SDK examples. The core is a Pregel-inspired execution engine: `StateGraph` compiles user-defined nodes and conditional edges into a `Pregel` runnable, where typed state channels (`LastValue`, `Topic`, `DeltaChannel`) apply reducer-based updates across supersteps. The engine supports durable checkpointing (in-memory, SQLite, Postgres), interrupts for human-in-the-loop, retry/timeout policies, subgraph composition, and v3 streaming. The CLI can scaffold projects and deploy graphs to LangGraph Cloud or self-hosted runtimes via Docker; the SDK provides sync/async clients that drive remote graphs over HTTP/SSE/WebSocket with typed stream projections (messages, tool calls, lifecycle). This is purely an application/framework repo; the `examples/` notebooks are usage demonstrations, not research pipelines. Primary data flow: user code builds a graph and compiles it; invocation reads channel state from a `BaseCheckpointSaver`, runs eligible nodes (with optional caching/retry), applies channel updates via reducers, writes the new checkpoint per superstep, and emits streamed events through a transformer pipeline (`StreamMux`). The SDK's v3 streaming protocol adds reconnection, subscription fan-out, and scoped subgraph handles over an SSE/WebSocket transport. External dependencies center on `langchain-core` (messages, tools, runnables), Pydantic, `httpx`, `psycopg`, `msgpack`, `orjson`, with optional `redis` and `pycryptodome` for cache/encryption. The codebase exhibits exceptional engineering: extensive unit/integration/conformance tests, a formal conformance suite that pins checkpoint-backend behavior across implementations, security-conscious serialization (strict msgpack/json module allowlists, a patched path-traversal vulnerability in the SDK), and benchmarks. Notable weaknesses are real but contained: heavy sync/async duplication in SDK clients and transports, a fast-moving deprecation path (many renamed APIs, `MessageGraph` slated for removal), and beta features (`DeltaChannel`, `ServerRuntime`) marked unstable. The `@task`/`@entrypoint` functional API, `create_react_agent` prebuilt, and conformance test framework are the most stable and reusable surfaces.

This repository is a comprehensive, multi-package AI agent framework developed by LangChain, known as 'Deep Agents'. It provides a production-ready SDK ('deepagents') built on LangGraph for creating stateful, middleware-driven agents with capabilities such as filesystem manipulation, shell execution, memory, sub-agents, skills, human-in-the-loop, and summarization. The primary client is a high-quality CLI/TUI application ('deepagents-code') that offers an interactive coding assistant with a rich Textual terminal interface, plugin system, MCP OAuth integration, and sandboxed execution via multiple providers (Daytona, Modal, Runloop, Vercel). A deployment CLI ('deepagents-cli') manages agent lifecycle on LangSmith, and an experimental persistent runtime ('talon') supports cron jobs, voice, and channels like Telegram/WhatsApp. A comprehensive evaluation suite ('evals') includes benchmarks (FRAMES, Nexus, BFCL, tau2, MemoryAgentBench, Context-Bench, DRBench) with LLM-as-judge, trajectory scoring, and LangSmith reporting. The architecture emphasizes modularity: middleware stack, hooks system, backend protocols, and profile system. While primarily an application, the evals and dataset curation give it a hybrid character.

This is a LangGraph-based web research assistant that runs fully locally. It accepts a research topic, then enters a loop: an LLM (Ollama or LMStudio) generates a web search query, a configurable search API (DuckDuckGo, Tavily, Perplexity, or SearXNG) fetches results, the same LLM summarizes the findings and reflects on knowledge gaps to generate follow-up queries. After a configurable number of iterations, it produces a final markdown summary with deduplicated source citations. The architecture is a clean state graph with six nodes and conditional routing, all orchestrated via LangGraph's compile and run mechanism. It is deployed as a LangGraph dev server or via Docker. The codebase demonstrates solid LangGraph patterns, proper separation of concerns (configuration, state, utilities, prompts, graph definition), and a smart abstraction for switching between JSON mode and tool calling for structured LLM output. Notable craft includes the `generate_search_query_with_structured_output` helper that cleanly handles fallback and the `ChatLMStudio` adapter for LMStudio's OpenAI-compatible API.

This repository is an educational tutorial for learning LangChain, LangGraph, and Deep Agents frameworks. It contains two tracks: 101 (fundamentals) and 201 (production patterns) with Jupyter notebooks and standalone agents runnable via `langgraph dev`. The code demonstrates multi-agent supervision, human-in-the-loop interrupts, middleware hooks, MCP tool integration, and a deep research agent with skills and memory. All agents use mock or simulated data (Chinook SQLite, Tavily search) and are designed for learning rather than production. The architecture centers on a centralized model configuration (`utils/models.py`) that supports multiple LLM providers, and reusable patterns like subgraph composition, dynamic prompts, and composite backends. While the code is educational and lacks production hardening (error handling, testing, security), it provides clear, well-commented examples of advanced agent patterns.