Anthropic, the company behind Claude, widely considered one of the most capable AI systems available today, did not build seven completely different models. What they built is simpler than it first appears. It is one system, organized as a ladder. The names can sound confusing at first, but in practice there are only five levels to understand, moving from fast and efficient to increasingly powerful forms of reasoning. Once you understand this ladder, the system becomes much easier to use.
A therapist recently said, “I keep hearing different names, Haiku, Sonnet, Opus, and I don’t know which one I should use.” This is a very common experience. The difficulty is not the technology itself, but how it is presented. When there are too many names, it starts to feel complicated very quickly.
A more helpful way to understand Claude is this: it is not many separate AI systems. It is one system organized as a ladder. Each name represents a different level of ability, moving from fast and simple to more powerful and complex. Once you see it this way, the confusion becomes much easier to manage.
At the lowest level is Haiku. This is the fastest and most affordable option. It works well for simple, repetitive tasks that do not require deep thinking. For example, a therapist might use Haiku to summarize session notes, rewrite a paragraph, or organize brief information. It is helpful for saving time, but it is not designed for complex clinical reasoning.
The next level is Sonnet, and this is the model most clinicians will find useful in everyday work. It offers a good balance between quality and cost. Sonnet can support tasks like writing case notes, developing treatment plans, or creating psychoeducational material. It is reliable and clear, without being too resource-intensive. For many therapists, this becomes the default choice.
Above that is Opus, which is designed for more demanding thinking. This is the model to use when the work becomes more complex, such as exploring case formulations, comparing diagnostic possibilities, or integrating research into practice. It can handle more depth, but it also requires more resources, so it is usually best used when needed rather than all the time.
At the top of the ladder are Fable and Mythos. These are not two different systems, but the same model with different settings. Fable includes safety guardrails, meaning it is more cautious when responding to sensitive or high-risk topics. Mythos has fewer restrictions and allows more open responses, but it is typically limited to expert use. For most clinical settings, Fable is the more appropriate and responsible choice.
However, a recent development adds a key limitation: the US government has issued an export control directive suspending access to Fable 5 and Mythos 5 for foreign nationals, both inside and outside the United States. As a result, these systems may be abruptly unavailable to many users in practice.
Thinking in terms of a ladder can help guide decisions in practice. Instead of asking, “Which model is best?”, it is more useful to ask, “How much support do I need for this task?” Simple tasks can stay at the lower levels, while more complex clinical questions may require moving higher. This approach is similar to how therapists already adjust interventions based on client needs.
It is also important to remember that these tools support thinking, but do not replace clinical judgment. AI can help organize ideas, suggest possibilities, or clarify language, but it does not fully understand the client or the therapeutic relationship. The clinician remains responsible for interpreting and deciding what is appropriate.
There are also ethical considerations to keep in mind. When using AI in clinical or research settings, it is important to be transparent about how it is used and to ensure that sensitive information is handled carefully. Clinicians should also be aware that AI systems can reflect biases or make errors, even when responses sound confident. Careful review and critical thinking are always necessary.
As these tools become more common, they may begin to shape how clinicians write, think, and communicate. This creates new opportunities, but also new responsibilities. It will be important to continue reflecting on how AI fits into clinical practice, rather than using it automatically or without question.
In the end, the goal is not to master every model or feature. It is simply to understand the basic structure: one ladder, with different levels of support. With this perspective, AI becomes less overwhelming and more practical. It can then serve as a helpful extension of clinical work, while the therapist remains at the center of decision-making and care.