Claude Opus 4 vs Sonnet 4 vs Haiku 3.5: functionalities, performance and practical differences between the models available today.

Today the models actually available to Claude subscribers are three.

Anyone subscribing today will only find Opus 4, Sonnet 4, and Haiku 3.5 among the accessible choices.

For those with a Claude subscription—be it Pro, Max, Team, or Enterprise—the model selection is limited to the three main names: Claude Opus 4, Claude Sonnet 4, and Claude Haiku 3.5. Models from previous generations, such as Opus 3 or Sonnet 3.5, are now labeled as “legacy” and have disappeared from the standard interface, remaining accessible only via API for compatibility with pre-existing projects if necessary.

Each model meets different practical needs and offers a specific mix of power, speed, and costs.

The main differences in power and target use are clearly visible among the three models.

Claude Opus 4 is the top-tier model, designed for the most complex tasks that require deep reasoning, processing of large data sets, or projects where precision is not negotiable. It offers a context window of 200,000 tokens (up to 1 million for Enterprise), with a maximum output of 32,000 tokens and the well-known “extended thinking” mode, which allows the model to solve complicated problems by allocating more computational resources and processing time.

Claude Sonnet 4 is conceived as a balanced solution for most professional uses. It maintains the same context width as Opus 4 but brings the maximum output to 64,000 tokens. It responds very quickly—often in less than a second—and can also activate “extended thinking” to achieve higher accuracy. It is the most suitable choice for corporate chats, customer care, text generation, and mid-high volume automations.

Claude Haiku 3.5 favors absolute speed and handling of large numbers of light requests, ideal for brainstorming, instant replies, autocompletion, and real-time moderation. It offers the same context window as the other models (200,000 tokens), but the maximum output per turn is limited to 8,000 tokens and it does not have the extended reasoning mode.

All current models share some key functionalities useful in professional settings.

Vision, integrated tools, code execution, and data management are transversal elements.

All three current models—Opus 4, Sonnet 4, Haiku 3.5—allow for image analysis (up to 100 images per turn), interpretation of tables, charts, and diagrams, as well as integration with custom tools via API. Each allows the execution of Python code in an isolated environment, search on external sources (RAG), and the use of advanced retrievals. However, only Opus 4 and Sonnet 4 enable the “extended thinking” mode, while Haiku focuses entirely on speed.

It is worth noting Anthropic’s choice not to implement persistent memory for the user: any historical customization or long-term memory must be integrated through external systems via API.

Usage limits and the management of “extended thinking” minutes vary depending on the selected plan.

Different subscriptions provide access to different minutes and contexts for every need.

In the free plan, the user can only select Sonnet 4, with a very low daily limit for the “extended thinking” mode (about 5 minutes per day). Pro and Max plans unlock all models, raising the limit to 30 or 120 minutes per day respectively, while Team or Enterprise plans offer even higher custom limits and wider contexts. This logic of limits applies both on the web and on mobile apps, and the model can be changed even during an ongoing conversation.

The choice of the most suitable model depends on the task and the required depth of analysis.

Every practical use finds its ideal model among the three available today.

Opus 4 is the right choice for activities where accuracy, deep reasoning, advanced automation, complex code refactoring, or the preparation of complex documents and specialized reports are needed.

Sonnet 4 is perfect for business needs like chatbots, customer support, and technical text generation, combining speed and reasoning.

Haiku 3.5 is irreplaceable when speed of response over large volumes or handling simple, repetitive tasks becomes the priority.

The API identifiers change according to the version and are updated periodically.

Each model has a dedicated and well-documented API endpoint.

Those integrating Claude into their applications will find these updated codes:– Claude Opus 4: claude-opus-4-20250514– Claude Sonnet 4: claude-sonnet-4-20250514– Claude Haiku 3.5: claude-3-5-haiku-20241022The old “legacy” models are now excluded from the standard interfaces and can only be called in specific contexts via API.

Some practical tips help you make the most of the Claude platform.

It is convenient to alternate speed and depth by leveraging the flexibility of the models.

Enabling “extended thinking” mode only when truly needed allows you to optimize costs and daily limits. For batch activities or prompt caching, Anthropic offers significant discounts that make mass automation more convenient. Sending images before text significantly increases the accuracy of visual analysis, while for any need for memory or personalization, you must rely on external systems. The possibility of changing the model in real time represents real operational flexibility for those working in professional contexts.

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