Chain of Thought & Reasoning Architecture

A New Paradigm in AI

The reasoning model family (o1 → o3 → GPT-5.4 Thinking) represents a fundamental shift. Instead of generating answers token-by-token immediately, they use reinforcement learning to generate a hidden Chain of Thought (CoT) before producing the final output.

The Evolution

How Reasoning Models Think

1. Break the problem into smaller steps.
2. Try different approaches.
3. Recognize mistakes and backtrack.
4. Synthesize a final, accurate answer.

Prompting Reasoning Models

• Keep it simple: State the problem directly. Do NOT say "think step by step."
• Provide edge cases: Give constraints the model should consider.
• Use the developer role: Reasoning models use developer instead of system.

// Reasoning models use the "developer" role:
const response = await openai.responses.create({
  model: "gpt-5.4-thinking",
  reasoning: { effort: "high" },  // low | medium | high
  input: [
    { role: "developer", content: "You are a math olympiad judge. Be rigorous." },
    { role: "user", content: "Prove that sqrt(2) is irrational." }
  ]
});