ReAct: Synergizing Reasoning and Acting in Language Models
Shunyu Yao et al. · ICLR 2023
arXiv:2210.03629
In short
ReAct has a language model alternate between writing a thought and taking an action, such as a search, then reading the result before its next thought. Grounding reasoning in real observations cuts hallucination and beats reasoning-only or acting-only prompting.
Why it matters
The think–act–observe loop in ReAct is the skeleton of nearly every LLM agent and coding harness today.
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The 4 Field Guide ideas this paper leans on.
Starting from scratch? The full route 23 ideas · basics first
- Natural Language Processing ✓ understood
The field of AI that lets computers read, interpret, translate and generate human language, from spam filters and search to chatbots.
- Token ✓ understood
The basic unit of text that a language model processes, typically representing a word, subword, or character. Tokens are the fundamental building blocks for LLM input and output.
- Tokenization ✓ understood
Splitting text into tokens, usually subword pieces, and mapping each to an integer ID so a language model can process it.
- Language Modeling ✓ understood
Learning probability distributions over sequences of words to predict what comes next.
- Dataset ✓ understood
A collection of data examples used for training, validating, or testing machine learning models.
- Training ✓ understood
The process of fitting a model to data by repeatedly measuring how wrong its outputs are and adjusting its parameters to reduce that error.
- Machine Learning ✓ understood
Building systems that learn patterns from data instead of following hand-written rules, getting better at a task as they see more examples.
- Unsupervised Learning ✓ understood
Learning from unlabeled data to discover hidden patterns, structures, or relationships without explicit target outputs.
- Self-Supervised Learning ✓ understood
Learning representations from unlabeled data by creating supervised tasks from the data itself (masked prediction, contrastive learning).
- Pre-training ✓ understood
Training a model on a large dataset (often self-supervised) before fine-tuning on specific tasks, enabling transfer learning.
- Feature ✓ understood
A single measurable property of an example, such as a house's floor area or how many links an email contains, used as an input to a model.
- Neural Network ✓ understood
A computational model inspired by biological neural networks, consisting of interconnected nodes (neurons) organized in layers that process information through weighted connections.
- Deep Learning ✓ understood
A subset of machine learning that uses neural networks with multiple layers (deep neural networks) to learn hierarchical representations of data.
- Representation Learning ✓ understood
Learning useful features or representations of data automatically, rather than hand-crafting them.
- Embedding ✓ understood
A list of numbers (a vector) that represents a word, sentence, image or other item, learned so that similar items end up close together.
- Attention Mechanism ✓ understood
A technique that lets a neural network weigh every part of its input when producing each output, focusing on the parts most relevant at that step.
- Transformer ✓ understood
A neural network architecture, introduced in 2017, built from stacked self-attention and feed-forward layers; the basis of nearly every modern large language model.
- Large Language Model · read first ✓ understood
A neural network, almost always a transformer, trained on vast amounts of text to predict the next token, which lets it write, answer, summarize and follow instructions.
- Prompt Engineering ✓ understood
The practice of designing and optimizing input prompts to get desired outputs from language models. A crucial skill for effectively using LLMs.
- Chain-of-Thought · read first ✓ understood
A prompting technique where the model explains its reasoning step-by-step before giving a final answer, improving complex reasoning.
- Tool Use · read first ✓ understood
LLMs learning to call external tools, APIs, or functions to extend capabilities beyond text generation (calculators, search, code execution).
- Context Window ✓ understood
The maximum number of tokens an LLM can process at once, including both input prompt and generated output. Also called context length.
- AI Agent · read first ✓ understood
A system where a large language model decides its own next steps in a loop: calling tools, reading the results, and continuing until the task is done.