Claude Opus 4.5

Gold definitionUpdated Apr 2, 2026

Definition

Claude Opus 4.5 is a powerful large language model (LLM) serving as a base model for advanced agentic systems, particularly excelling as a general coding agent. It enables complex reasoning tasks like formal theorem proving, achieving state-of-the-art performance by coordinating with tools and specialized modules.

At a glance

Executive summary

Claude Opus 4.5 is a powerful AI model that acts as the brain for advanced AI agents, especially those that write code and solve complex problems. It helps these agents perform tasks like proving math theorems by allowing them to use various tools and adapt without needing to be retrained for every new task.

TL;DR

Claude Opus 4.5 is a top-tier AI model used as the core intelligence for smart coding agents that can solve hard problems and use tools flexibly.

Key points

Serves as a general coding agent and base LLM for agentic systems, providing a natural interface for diverse reasoning tasks.
Enables flexible, extensible, and high-performing autonomous agents for complex tasks like formal theorem proving without task-specific training.
Used by researchers and engineers developing advanced AI agents for formal verification, software automation, and complex problem-solving.
Improves performance by model replacement rather than extensive task-specific pipeline training, offering greater flexibility than specialized formal provers.
Central to the paradigm of using general coding agents as formal reasoners, pushing the boundaries of autonomous AI in complex domains.

Use cases

Formal Theorem Proving: Powering agents like Numina-Lean-Agent to solve challenging mathematical problems and verify proofs in systems like Lean.
Automated Software Engineering: Acting as the core of autonomous coding agents to automate complex development tasks, from code generation to debugging.
AI-Assisted Research: Enabling agents to retrieve information, perform auxiliary reasoning, and interact with specialized scientific tools.
Complex Problem Solving: Serving as the reasoning engine for agents tackling multi-step, open-ended problems requiring tool use and dynamic adaptation.

Also known as

Claude Opus