Which AI Chatbots Have “Deep Reasoning” Features?

Today, more people are turning to chatbots for serious help—this might mean researching a technical topic, analyzing business contracts, or untangling complex academic questions. The difference between a basic chatbot and a truly helpful one often comes down to a capability called “deep reasoning”

Deep Reasoning is the ability to break down complex questions, follow logical steps, and give a thoughtful, step-by-step explanation instead of a rushed response. But not all AI chatbots are created equal in this area, and some offer special models or features specifically designed for users who want their chatbot to “think harder.”

What Is Deep Reasoning in AI Chatbots?

When we talk about deep reasoning, we’re referring to an AI’s ability to truly engage with a complex problem. Instead of grabbing the first fact it finds, a chatbot with deep reasoning can break down a big question into smaller, logical steps. It follows chains of logic, keeps track of multiple details, and provides an answer that is clear and well-explained. This skill is essential for students needing help with math proofs, researchers analyzing lengthy texts, or professionals working through complicated business scenarios.

ChatGPT (OpenAI)

Among all the AI chatbots available today, OpenAI’s ChatGPT remains one of the most familiar and trusted. Over the past year, ChatGPT’s ability to reason deeply has improved tremendously, especially with the introduction of new model families specifically built for logic and careful, step-by-step thinking. In 2025, users can access several versions of ChatGPT, each with different strengths.

The GPT-4o model (the “o” stands for “omni”) is the fast, all-purpose choice used by millions for daily questions, writing, and also image or voice-based tasks. But for deep reasoning—tasks like reading and understanding long legal documents, solving tricky technical problems, or tracking many details across a big conversation—OpenAI now offers the o3 and o3-pro models.

Let's see how deep reasoning technically works on this platform.

When you use ChatGPT, you start by picking your model in the menu (on the web, mobile app, or integrated tools). The “o3” and especially “o3-pro” models are engineered to allow more deliberation time per response. In technical terms, these models use more compute cycles and are allowed to run more “forward passes” (the internal steps the model takes to generate each token, or word). This means that when faced with a complex question, they can simulate thinking step-by-step, rather than just jumping to the most likely answer based on their training.

For example, if you ask a math problem or a multi-part research question, o3 and o3-pro break the input into logical pieces internally. They keep an expanded “working memory” of the conversation so they can refer back to previous details, and may use a built-in “chain-of-thought” prompting system—where the model is guided to reason through the answer out loud, listing steps before giving a final conclusion. Under the hood, this involves mechanisms like self-consistency sampling (running the model through the problem multiple times and comparing reasoning paths) and, for advanced users, can also include tool use (where the model calls built-in calculators, code runners, or web search plugins to check steps).

As a user, you see this in the form of more detailed, step-by-step answers—often with the model first outlining assumptions or laying out each calculation or logical step before the summary. If you explicitly ask “Please explain this step by step” or “List your assumptions,” the model’s output will reflect that, showing you its whole thought process.

Practically, standard “Plus” users (around €24/month) can use GPT-4o and o3 with a weekly message limit. The “o3-pro” model is only available to business-focused plans—such as ChatGPT Team, Enterprise, Education, or the premium “Pro” research subscription—since it uses even more computational resources and is designed for very heavy or sensitive tasks.

Overall, the technical deep reasoning in ChatGPT comes from how these models are allowed to slow down, simulate many steps in their logic, and check their own work before sharing a final answer—making the process as transparent as possible for you.

Claude (Anthropic)

Another top performer in deep reasoning is Claude, created by Anthropic. Claude is well-known for providing highly thoughtful, context-aware answers, especially for questions that require actual logic or balancing different points of view.

Claude is available via its web interface at claude.ai, on iOS, and through APIs (like Amazon Bedrock and Google Vertex AI). In 2025, the models best suited for deep reasoning are Claude Opus 4 (the most careful and detailed) and Claude Sonnet 4 (faster but still logical).

What’s unique about Claude’s deep reasoning process is that it relies on both model design and dynamic response scaling. Technically, Claude Opus 4 is built with a huge context window, meaning it can remember and reference more of your conversation and any long documents you upload—sometimes hundreds of thousands of words. When Claude detects a question that looks complicated (such as a request for ethical analysis, long-form research, or comparing legal arguments), it automatically enters what Anthropic calls “extended thinking.”

During extended thinking, Claude breaks down your input internally into separate reasoning threads. It may run through multiple possible logic paths, compare them, and then assemble a response that includes the pros and cons, potential errors, or different viewpoints. Under the hood, Claude also uses techniques like chain-of-thought prompting (where the model is instructed to explain every step before drawing a conclusion) and sometimes a process called “reflection”—where the model double-checks its own output before returning the answer to you. This is done by re-feeding its own answer back into itself, asking, “Is there a possible mistake in this reasoning?” or “Can I improve the logic?”

For you, this results in a highly organized answer: Claude might lay out assumptions first, then walk through each logical or calculation step, and finally summarize the findings. If you ask for even more structure (“Please list your steps before answering” or “Break this down into bullet points and then explain”), Claude will follow these instructions and make its thinking very transparent.

Anthropic’s free tier lets you use Sonnet 4 with some limits. For full access to Opus 4 and heavier use, the paid “Pro” plan (about €20/month) is available. Businesses and organizations can use Team or Enterprise tiers for even higher usage caps.

What makes Claude’s deep reasoning so effective is the technical foundation—large context, chain-of-thought prompting, reflection, and self-checks—all designed to maximize logical accuracy and transparency. The result is an AI that doesn't just give answers, but tries to show you how and why it reached its conclusion, every step of the way.

Gemini (Google DeepMind)

Google’s Gemini chatbot, developed by DeepMind, has also made big strides in deep reasoning. The most advanced model, Gemini 2.5 Pro, now includes an experimental “Deep Think” setting that’s specifically designed for big, careful, and complicated questions. When you want to analyze a long scientific article, pull insights from a large data set, or get a step-by-step explanation of a challenging topic, Gemini 2.5 Pro is Google’s best tool for the job.

Gemini can be accessed through its dedicated mobile app or web interface at gemini.google.com, and it’s also being built into Google Workspace tools like Gmail, Docs, and Sheets. For developers, the Gemini API is available through Vertex AI and AI Studio. Gemini’s basic version is free to everyone, but the “AI Pro” plan (about €20 per month) unlocks Gemini 2.5 Pro and its Deep Think mode. Google also offers a higher “AI Ultra” tier with additional features for power users, and students can get AI Pro for free during the academic year.

To get the most out of Gemini’s deep reasoning abilities, you select the 2.5 Pro model in your settings or ask for “Deep Think” when you’re working with big or complex questions. The chatbot then takes its time, considers your question carefully, and walks you through the logic step by step.

Meta AI (Llama 4)

Meta’s AI assistant, powered by the Llama 4 model, is now widely available across WhatsApp, Instagram, and Facebook Messenger, as well as in a standalone Meta AI app and even smart glasses. Unlike some of its competitors, Meta AI doesn’t offer a specific deep reasoning mode or model. However, Llama 4 is capable of logical, step-by-step answers if you prompt it the right way.

You can use Meta AI for free in all supported apps by tagging “@Meta AI” in your conversation. If you want the chatbot to reason more deeply, it’s best to ask it to “explain your reasoning,” “analyze each step,” or “show your thinking.” While Meta AI may not match the ultra-detailed performance of ChatGPT o3-pro or Claude Opus 4, it still does a solid job of working through everyday logic and complex conversations, all without a subscription fee. Meta is rumored to be testing a premium “Meta AI+” tier, but as of now, all users can access

Llama 4 and its reasoning abilities for free.

Grok (xAI / X.com)

Grok, created by Elon Musk’s xAI and available inside X (formerly Twitter), offers a playful and sometimes witty approach to deep reasoning. The latest Grok-3 model includes special “Think” and “Big Brain” toggles, which users can activate to see the chatbot’s full chain of logic and get more thoughtful, step-by-step answers. When you tap one of these modes, Grok spends extra time and computing resources to break down your question in detail, instead of giving you a quick summary.

You can access Grok in the X web and mobile apps, or on the grok.com beta site. There’s a basic free tier with limits on how many “Think” messages you can send, and two paid plans—Premium+ (about €40-50/month, depending on the region) and SuperGrok (about €30/month extra)—that remove these limits and unlock all deep reasoning features, including the Big Brain mode and voice interactions.

Grok’s personality is a bit more casual than some of the others, but when you want a chatbot to “show its work” or explain its thinking in detail, these special modes make it a strong choice—especially for users who spend a lot of time on X.

Constella App

Constella is a unique “second-brain” app that lets you organize your notes and thoughts, then pipe them directly into your choice of AI chatbot for advanced reasoning. Rather than building its own large language model, Constella acts as a bridge: you can connect ChatGPT, Claude, Gemini, or other leading chatbots, and then send entire graphs of your notes to whichever model you choose.

The depth of reasoning you get from Constella therefore depends entirely on which external model you connect. If you link it to ChatGPT o3-pro, you get the full power of that model’s deep reasoning; if you use Claude Opus 4, you get the best from Anthropic. Constella offers a basic “Starter” plan (about €6/month) with limited AI usage, and a “Star” plan (about €15/month) that enables more advanced features like “context stitching” and higher AI minute limits. You can use Constella on macOS, the web, and in a mobile beta app, and there’s a 14-day free trial for new users.

Getting the Most Out of Deep Reasoning

No matter which chatbot you choose, you can encourage deeper, more thoughtful answers by asking the AI to “think step by step,” “show your work,” or “explain your reasoning.” Always provide as much context as possible, and don’t hesitate to use the premium or advanced models if you’re tackling especially large or complex tasks. For chatbots with special reasoning modes or toggles—like Grok’s “Think” or Gemini’s “Deep Think”—make sure to turn them on when you want the bot to work harder on your problem.

So... in 2025, users have a wide range of options when it comes to AI chatbots that can truly “think things through.” OpenAI’s ChatGPT, especially in the o3-pro model for research and business users, and Anthropic’s Claude Opus 4 lead the way for research, business, and technical analysis. Google’s Gemini 2.5 Pro is an excellent choice for long and complex queries, while Meta AI offers solid, free reasoning for day-to-day tasks. Grok stands out for its interactive “Think” mode inside X, and Constella gives you the freedom to bring deep reasoning to your personal notes using any of the major external models.

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