PrecisionAI Thinking Modes Explained
TL;DR;
AI models operate in two modes: Non-Reasoning (Fast) and Reasoning (Deep Think). Choose the right one to save money and improve results.
- Fast Models are intuitive, quick, and cheap. Best for simple, high-volume tasks. They need long, structured prompts to prevent making things up (hallucination).
- Deep Think Models are slow, deliberate, and expensive. Essential for complex planning and critical analysis. They work best with simple, short prompts as they handle the complexity internally.
- Strategy: Start with the Fast Model by default. Only upgrade to the Deep Think Model if the task is complex, high-risk, or the Fast Model fails.
If you use tools like Gemini or Claude, you’ve probably noticed the option to switch between a “Fast” mode and a “Pro” or “Thinking” mode—and wondered what that choice actually does.
Is it just a speed setting, or does it change how the AI works under the hood? And when does picking the wrong one cost you accuracy, money, or both?
Most modern AI tools run in one of two modes: reasoning and non-reasoning. Here’s what those modes really mean, and when each one makes sense to use.
Fast Thinking vs. Deep Thinking
The Non-Reasoning Model is the Fast Thinker. It delivers quick, low-cost output using rapid pattern-matching. This makes it well suited to high-volume work—such as drafting multiple social posts or extracting simple data. The trade-off is accuracy control: it relies heavily on long, explicit prompts. Without clear rules, it will guess, increasing the risk of hallucination.
The Reasoning Model is the Deep Thinker. It is slower and more expensive because it plans and checks its logic before responding. This makes it better suited to complex or subjective tasks, such as analysing sentiment or solving multi-step problems. Because it handles the reasoning internally, it usually works well with shorter, simpler prompts.
Model Names
Here is a quick reference for the models you might encounter:
| AI Provider | Fast/Non-Reasoning Model | Deep Think/Reasoning Model |
|---|---|---|
| Google Gemini | Gemini Flash series | Gemini Pro / Deep Think series |
| Anthropic Claude | Claude Haiku | Claude Sonnet or Opus |
| OpenAI GPT | GPT-4o Mini | GPT-4o or GPT-5.2 Thinking |
Things to try
Use this rule: Start fast, escalate only when needed.
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Drafting Social Media Copy (Fast Model): Use a Fast Model to generate five posts for a new product. Use a detailed prompt to lock down tone, length, and hashtags.
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Analysing Customer Feedback (Deep Think Model): Use a Deep Think Model to review comments and identify the most important emotional pain point. Ask for a conclusion with supporting evidence.
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Data Extraction from Documents (Fast Model): Use a Fast Model to extract client names, dates, and amounts from 20 invoices and return them as a table.
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Planning a Project Timeline (Deep Think Model): Use a Deep Think Model to produce a 90-day plan for a complex change, including dependencies and risks.
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Summarising a Long Report (Fast Model): Use a Fast Model to reduce a 5,000-word report to five bullet points for a team brief. Specify length and format.
Want to know more?
Now that you know how to pick the right AI “brain,” the next step is learning how to make the Deep Thinker work even harder for you. Run this prompt in any of your preferred AI models:
“I want to improve the quality of the answer I get for complex problems. Ask me three questions to clarify my goal, and then give me a simple rule I can add to any prompt that will force the model to ‘show its working’ before giving me the final answer.”