Claude Opus

basicwidespread

Claude Opus is the most knowledgeable and most expensive model in the Claude artificial intelligence family from the company Anthropic, designed for the most difficult tasks requiring extensive reasoning.

In plain terms

Anthropic releases its artificial intelligence, Claude, in several sizes, with Opus being the flagship model. Its smaller siblings are Sonnet (the mid-range, general-purpose model) and Haiku (the fastest and cheapest).

It is like a senior partner in a law firm: you do not have them write routine letters because they are expensive and slower, but you entrust them with complex, high-stakes cases. It is worth bringing out Opus when the task is long, complex, and errors are costly.

Typical use cases include analyzing long documents, multi-stage research, large-scale programming work, and operating agents that work independently on a task for hours.

'Opus' is not a single program but a level name. New versions are released periodically (for example, Claude 3 Opus, Opus 4, Opus 4.5), while older ones are gradually phased out.

How it works

Opus is a large language model: it was trained on vast amounts of text and learned from this how to carry out a coherent line of reasoning or solve a task.
When you ask it a question, it breaks your text into small pieces (tokens) and generates the answer step by step. For more difficult tasks, if this feature is enabled, it first 'thinks through' the solution and then answers.
This is the family's largest, most compute-intensive model, so it handles long, detail-heavy tasks better, but in return it is slower and more expensive than Sonnet or Haiku.
It can also receive tools: it can search the web, read files, and run programs. In this case, it functions as an agent, meaning it not only answers but also performs the work in multiple steps.
You can access it via the Claude app (typically with a subscription), while companies integrate it into their own services through a programming interface (API), paying based on the amount of text used.

An everyday example

You open the Claude application and can choose from several names in the model selector, such as Opus and Sonnet. If you want to extract pitfalls from an eighty-page contract, you choose Opus; if you just want to rewrite an email, the smaller model is more than enough and finishes faster.

Who is affected

developerCoding agents often run on Opus when they need to navigate a large codebase or complete a long, independent task. → Code

entrepreneur, executiveYou must decide which tasks are worth the more expensive top-tier model and where the cheaper, faster version is sufficient.

employeeFor analysis, report writing, or processing long materials, you can get noticeably more thorough work from it than from smaller models. → Work & HR

lawyer, citizenStrong in interpreting long, complex texts, but the user remains responsible for the results. → Law

A common misconception

MythAlways use Opus because it is the best.

In realityFor most everyday tasks, smaller models deliver equally good results, faster and cheaper. Opus makes a difference where the task is truly long, complex, or high-stakes.

Limits and risks

Even the top model can err and confidently state falsehoods, so always verify important facts, numbers, and references.
It is more expensive and slower than its siblings, and subscription plans usually impose stricter usage limits.
Its knowledge extends only up to a specific date: it knows about recent events only if it is given a web search or your own document.
The versions behind the name change, so the same request may yield a different result in six months. Always check exactly which Opus version you are using.

Similar, but not the same

Claude – Claude is the name of the entire model family and the application; Opus is only the most capable tier within it.
Claude Sonnet – Sonnet is the family's mid-tier, faster and cheaper model designed for daily work, while Opus is intended for the most demanding tasks.
Claude Code – Claude Code is a programming assistant tool, a coding agent that uses a model, such as Opus, but is not the model itself.

Related concepts

Broader

Claude, Large language model, Foundation model, Generative AI

Narrower

Claude 3 Opus, Claude Opus 4, Claude Opus 4.1, Claude Opus 4.5

On the edge

Anthropic, Claude Sonnet, Claude Haiku, Claude Code, AI-agent

A brief history

The name Opus appeared in March 2024, when Anthropic released the Claude 3 family in three sizes (Haiku, Sonnet, Opus). Claude Opus 4 arrived in May 2025, followed by Opus 4.1 in August and Opus 4.5 in November, with the line continuing in 2026 with further versions.

Where things stand

By the end of 2026, Opus is Anthropic's flagship model line, available in the Claude app, through the developer API and from the major cloud providers. It is used mainly for complex professional work and for running agents that work independently over long periods.

Status: 2026 November

In the news

Appears in 15 Agent Age stories; the curve shows weekly occurrence in the news magazine.

Anthropic restricts Claude Code from cloning video gamesNov 2, 2026 · Code
GitHub Copilot Fusion mixes models to approach frontier coding performance at half the costOct 28, 2026 · Agent Age
Gemini 4 models in coding rankings: Carbon second, Argon trails on Android testOct 26, 2026 · Code
Cognition says Devin Fusion scores 68 on coding agent index at 31% lower costOct 19, 2026 · Code
Cursor agent wiped a production database and its backups in nine secondsOct 17, 2026 · Code
Developer builds free Adobe clones with Claude Opus 5.5Oct 8, 2026 · Code
Price war: GPT-6 Sol and Luna and Claude Opus 5.5 are cheaper than predecessorsSep 22, 2026 · Agent Age
Claude Opus 5.5 arrives in Claude Code, with pricing tied to longer coding sessionsSep 22, 2026 · Code

Also known as

Claude Opus · Opus · Opus modell · Claude 3 Opus · Claude Opus 4 · Claude Opus 4.1 · Claude Opus 4.5 · Anthropic Opus · Opus-modell

Sources

This entry was machine-edited and has undergone machine expert review; the “In the news” section updates automatically from Agent Age stories.