LLM Agent
An AI system that uses a large language model as its core reasoning engine, augmented with tools, memory, and planning capabilities to autonomously complete tasks.
Architecture
An LLM agent typically includes: (1) an LLM for reasoning and decision-making, (2) a set of tools it can invoke (search, code execution, APIs), (3) memory (conversation history, knowledge base), and (4) a planning module for breaking complex tasks into steps.
Frameworks
LangChain, LlamaIndex, AutoGPT, CrewAI, Claude Agent SDK, and OpenAI Assistants API provide building blocks for LLM agents. ReAct (Reason + Act) is a foundational pattern where the agent alternates between thinking and acting.
Current State
LLM agents can handle many multi-step tasks but still struggle with long-horizon planning, error recovery, and tasks requiring precise reasoning. The field is rapidly evolving with better tool use, memory systems, and evaluation frameworks.